Race Condition
Race conditions occur when multiple concurrent requests exploit the brief time gap between checking a condition and acting upon it (TOCTOU - Time of Check, Time of Use).
How It Works
Race conditions occur when multiple concurrent requests exploit the brief time gap between checking a condition and acting upon it (TOCTOU - Time of Check, Time of Use). An attacker sends nearly simultaneous requests to manipulate shared state before the application can enforce its business logic. For example, when redeeming a gift voucher, Request A checks the balance, Request B also checks while A is processing, then both complete successfully—redeeming the voucher twice.
Attackers use specialized techniques to achieve precise timing. HTTP/2's multiplexing allows 20-30 requests in a single TCP packet, arriving virtually simultaneously at the server. For HTTP/1.1, "last-byte synchronization" holds back the final byte of multiple requests, then releases them together. These methods reduce network jitter to microseconds, maximizing collision probability.
Advanced attacks include multi-endpoint collisions (hitting different API paths that share state), exploiting partial object construction (accessing resources before initialization completes), and single-endpoint confusion (causing a function to process stale state by overwhelming it with requests).
Impact
- Financial fraud: Redeeming coupons multiple times, withdrawing beyond account balance, applying discounts repeatedly
- Authentication bypass: Reusing CAPTCHA tokens, bypassing rate limits on login attempts, exploiting session validation gaps
- Resource exhaustion: Claiming limited inventory multiple times, booking the same seat/room concurrently
- Data corruption: Simultaneous writes creating inconsistent database states, inventory counts becoming negative
- Access control violations: Exploiting privilege checks to access unauthorized resources during state transitions
Real-World Examples
In 2019, security researchers demonstrated race conditions in major e-commerce platforms allowing users to purchase items at massive discounts by applying the same promotional code dozens of times within milliseconds. The applications checked voucher validity but didn't atomically mark them as used.
TOCTOU vulnerabilities have been found in cryptocurrency exchanges where concurrent withdrawal requests could drain more funds than an account held. Attackers automated HTTP/2 packet timing to submit multiple withdrawal requests before the balance update propagated, essentially duplicating money.
File upload race conditions have enabled remote code execution when attackers upload malicious files and execute them before security scanners complete validation-the check happens, but the file runs before removal.
Mitigation
- Database transactions with row-level locking: Wrap check-and-update logic in ACID transactions with SELECT FOR UPDATE
- Idempotency keys: Require unique request identifiers; reject duplicates within a time window
- Uniqueness constraints: Database-level UNIQUE constraints on critical fields (voucher redemptions, order IDs)
- Atomic operations: Use database built-ins like DECREMENT with bounds checking, compare-and-swap primitives
- Application-level mutexes: Distributed locks (Redis, memcached) around critical sections, ensuring single execution
- Rate limiting per resource: Throttle requests per user AND per target resource (not just per IP)
- Sequence validation: Check monotonically increasing counters or nonces to detect concurrent modification
Recent CVEs (2128)
An elevation of privilege vulnerability exists due to a race condition in Windows Subsystem for Linux, aka 'Windows Subsystem for Linux Elevation of Privilege Vulnerability'. Rated high severity (CVSS 7.0).
Possible use after free issue due to race condition while attempting to mark the entry pages as dirty using function set_page_dirty() in Snapdragon Auto, Snapdragon Compute, Snapdragon Consumer IOT,. Rated high severity (CVSS 8.1), this vulnerability is remotely exploitable, no authentication required.
In Magento prior to 1.9.4.3, Magento prior to 1.14.4.3, Magento 2.2 prior to 2.2.10, and Magento 2.3 prior to 2.3.3 or 2.3.2-p1, an authenticated user with administrative privileges for the import. Rated medium severity (CVSS 6.6), this vulnerability is remotely exploitable. No vendor patch available.
Sudo through 1.8.29 allows local users to escalate to root if they have write access to file descriptor 3 of the sudo process. Rated high severity (CVSS 7.0). Public exploit code available and no vendor patch available.
An issue was discovered in drivers/media/platform/vivid in the Linux kernel through 5.3.8. Rated high severity (CVSS 7.0). Public exploit code available.
An issue was discovered in Xen through 4.12.x allowing x86 PV guest OS users to gain host OS privileges by leveraging race conditions in pagetable promotion and demotion operations. Rated high severity (CVSS 7.5), this vulnerability is remotely exploitable.
Adobe Acrobat and Reader versions , 2019.012.20040 and earlier, 2017.011.30148 and earlier, 2017.011.30148 and earlier, 2015.006.30503 and earlier, and 2015.006.30503 and earlier have a race. Rated high severity (CVSS 8.1), this vulnerability is remotely exploitable, no authentication required.
A vulnerability has been found in the implementation of the Label Distribution Protocol (LDP) protocol in EOS. Rated medium severity (CVSS 5.9), this vulnerability is remotely exploitable, no authentication required. No vendor patch available.
A race condition which may occur when discarding malformed packets can result in BIND exiting due to a REQUIRE assertion failure in dispatch.c. Rated medium severity (CVSS 5.9), this vulnerability is remotely exploitable, no authentication required. No vendor patch available.
An issue was discovered in Xen through 4.11.x allowing x86 PV guest OS users to cause a denial of service or gain privileges by leveraging a race condition that arose when XENMEM_exchange was. Rated high severity (CVSS 7.0).
An issue was discovered in Xen through 4.11.x allowing x86 PV guest OS users to cause a denial of service or gain privileges by leveraging a page-writability race condition during addition of a. Rated high severity (CVSS 7.8).
Possible use-after-free issue due to a race condition while calling camera ioctl concurrently in Snapdragon Compute, Snapdragon Consumer IOT, Snapdragon Industrial IOT, Snapdragon Mobile, Snapdragon. Rated high severity (CVSS 7.0).
In hostapd, there is a possible out of bounds write due to a race condition. Rated medium severity (CVSS 6.4). No vendor patch available.
In the Easel driver, there is possible memory corruption due to race conditions. Rated medium severity (CVSS 6.4). No vendor patch available.
In the Easel driver, there is possible memory corruption due to race conditions. Rated medium severity (CVSS 6.4). No vendor patch available.
The Mozilla Maintenance Service does not guard against files being hardlinked to another file in the updates directory, allowing for the replacement of local files, including the Maintenance Service. Rated high severity (CVSS 7.0). No vendor patch available.
A race condition in specific microprocessors using Intel (R) DDIO cache allocation and RDMA may allow an authenticated user to potentially enable partial information disclosure via adjacent access. Rated medium severity (CVSS 4.8). No vendor patch available.
The File Session Manager in Beego 1.10.0 allows local users to read session files because there is a race condition involving file creation within a directory with weak permissions. Rated medium severity (CVSS 4.7). No vendor patch available.
An issue was discovered in GitLab Community and Enterprise Edition before 11.8.9, 11.9.x before 11.9.10, and 11.10.x before 11.10.2. Rated medium severity (CVSS 5.3), this vulnerability is remotely exploitable. Public exploit code available and no vendor patch available.
In the Android kernel in the video driver there is a use after free due to a race condition. Rated high severity (CVSS 7.0).
In the Android kernel in the FingerTipS touchscreen driver there is a possible memory corruption due to a race condition. Rated medium severity (CVSS 6.4).
In the Android kernel in the mnh driver there is a race condition due to insufficient locking. Rated medium severity (CVSS 6.4). No vendor patch available.
In FreeBSD 12.0-STABLE before r351264, 12.0-RELEASE before 12.0-RELEASE-p10, 11.3-STABLE before r351265, 11.3-RELEASE before 11.3-RELEASE-p3, and 11.2-RELEASE before 11.2-RELEASE-p14, the kernel. Rated high severity (CVSS 7.5), this vulnerability is remotely exploitable, no authentication required, low attack complexity. No vendor patch available.
A use-after-free flaw in the sandbox container implemented in cmdguard.sys in Comodo Antivirus 12.0.0.6870 can be triggered due to a race condition when handling IRP_MJ_CLEANUP requests in the. Rated medium severity (CVSS 4.7). Public exploit code available.
In ActivityManagerService.attachApplication of ActivityManagerService, there is a possible race condition. Rated high severity (CVSS 7.0). No vendor patch available.
Wind River VxWorks 6.9.4 and vx7 has a Buffer Overflow in the TCP component (issue 4 of 4). Rated high severity (CVSS 8.1), this vulnerability is remotely exploitable, no authentication required. No vendor patch available.
A race condition flaw was found in the response headers Elasticsearch versions before 7.2.1 and 6.8.2 returns to a request. Rated medium severity (CVSS 5.9), this vulnerability is remotely exploitable, no authentication required. No vendor patch available.
A race condition in the one-pass compression functions of Zstandard prior to version 1.3.8 could allow an attacker to write bytes out of bounds if an output buffer smaller than the recommended size. Rated high severity (CVSS 8.1), this vulnerability is remotely exploitable, no authentication required.
Race condition while accessing DMA buffer in jpeg driver in Snapdragon Auto, Snapdragon Connectivity, Snapdragon Consumer IOT, Snapdragon Industrial IOT, Snapdragon Mobile, Snapdragon Wearables in. Rated high severity (CVSS 7.0).
Possible race condition that will cause a use-after-free when writing to two sysfs entries at nearly the same time in Snapdragon Compute, Snapdragon Consumer IOT, Snapdragon Industrial IOT,. Rated high severity (CVSS 7.0).
A use-after-free vulnerability can occur in AssertWorkerThread due to a race condition with shared workers. Rated high severity (CVSS 8.1), this vulnerability is remotely exploitable, no authentication required. No vendor patch available.
A race condition is present in the crash generation server used to generate data for the crash reporter. Rated high severity (CVSS 8.3), this vulnerability is remotely exploitable, no authentication required. No vendor patch available.
A race condition occurs while processing perf-event which can lead to a use after free condition in Snapdragon Auto, Snapdragon Compute, Snapdragon Consumer IOT, Snapdragon Industrial IOT, Snapdragon. Rated high severity (CVSS 7.0).
In arch/x86/lib/insn-eval.c in the Linux kernel before 5.1.9, there is a use-after-free for access to an LDT entry because of a race condition between modify_ldt() and a #BR exception for an MPX. Rated high severity (CVSS 7.0). Public exploit code available.
On F5 SSL Orchestrator 14.1.0-14.1.0.5, on rare occasions, specific to a certain race condition, TMM may restart when SSL Forward Proxy enforces the bypass action for an SSL Orchestrator transparent. Rated medium severity (CVSS 5.9), this vulnerability is remotely exploitable, no authentication required. No vendor patch available.
modules/luksbootkeyfile/main.py in Calamares versions 3.1 through 3.2.10 has a race condition between the time when the LUKS encryption keyfile is created and when secure permissions are set. Rated high severity (CVSS 8.1), this vulnerability is remotely exploitable, no authentication required. Public exploit code available and no vendor patch available.
Incorrect security UI in popup blocker in Google Chrome on iOS prior to 75.0.3770.80 allowed a remote attacker to bypass navigation restrictions via a crafted HTML page. Rated medium severity (CVSS 4.3), this vulnerability is remotely exploitable, no authentication required, low attack complexity. No vendor patch available.
In createEffect of AudioFlinger.cpp, there is a possible memory corruption due to a race condition. Rated high severity (CVSS 7.5), this vulnerability is remotely exploitable, no authentication required. No vendor patch available.
In serviceDied of HalDeathHandlerHidl.cpp, there is a possible memory corruption due to a use after free. Rated critical severity (CVSS 9.8), this vulnerability is remotely exploitable, no authentication required, low attack complexity. No vendor patch available.
In callGenIDChangeListeners and related functions of SkPixelRef.cpp, there is a possible use after free due to a race condition. Rated high severity (CVSS 7.0), this vulnerability is no authentication required. No vendor patch available.
There is a race condition vulnerability on Huawei Honor V10 smartphones versions earlier than Berkeley-AL20 9.0.0.156(C00E156R2P14T8), Honor 10 smartphones versions earlier than Columbia-AL10B. Rated high severity (CVSS 7.0), this vulnerability is no authentication required. No vendor patch available.
An issue was discovered in GNOME gvfs 1.29.4 through 1.41.2. Rated high severity (CVSS 8.1), this vulnerability is remotely exploitable, no authentication required. No vendor patch available.
Data race in extensions guest view in Google Chrome prior to 73.0.3683.75 allowed a remote attacker to potentially exploit heap corruption via a crafted HTML page. Rated high severity (CVSS 7.5), this vulnerability is remotely exploitable, no authentication required. No vendor patch available.
A race condition in Intel(R) Graphics Drivers before version 10.18.14.5067 (aka 15.36.x.5067) and 10.18.10.5069 (aka 15.33.x.5069) may allow an authenticated user to potentially enable a denial of. Rated medium severity (CVSS 4.7). No vendor patch available.
An issue was discovered in rds_tcp_kill_sock in net/rds/tcp.c in the Linux kernel before 5.0.8. Rated high severity (CVSS 8.1), this vulnerability is remotely exploitable, no authentication required. Public exploit code available and no vendor patch available.
The groonga-httpd package 6.1.5-1 for Debian sets the /var/log/groonga ownership to the groonga account, which might let local users obtain root access because of unsafe interaction with logrotate. Rated high severity (CVSS 7.0). No vendor patch available.
The Siemens R3964 line discipline driver in drivers/tty/n_r3964.c in the Linux kernel before 5.0.8 has multiple race conditions. Rated high severity (CVSS 7.0).
The Linux kernel through 5.0.7, when CONFIG_IA32_AOUT is enabled and ia32_aout is loaded, allows local users to bypass ASLR on setuid a.out programs (if any exist) because install_exec_creds() is. Rated low severity (CVSS 2.5). Public exploit code available and no vendor patch available.
The Linux kernel before 4.8 allows local users to bypass ASLR on setuid programs (such as /bin/su) because install_exec_creds() is called too late in load_elf_binary() in fs/binfmt_elf.c, and thus. Rated medium severity (CVSS 4.7). Public exploit code available.
It was found that the net_dma code in tcp_recvmsg() in the 2.6.32 kernel as shipped in RHEL6 is thread-unsafe. Rated medium severity (CVSS 6.1), this vulnerability is low attack complexity.
In Apache HTTP Server 2.4 release 2.4.38 and prior, a race condition in mod_auth_digest when running in a threaded server could allow a user with valid credentials to authenticate using another. Rated high severity (CVSS 7.5), this vulnerability is remotely exploitable.
An issue was discovered in webargs before 5.1.3, as used with marshmallow and other products. Rated high severity (CVSS 8.1), this vulnerability is remotely exploitable, no authentication required. Public exploit code available and no vendor patch available.
In bta_hl_sdp_query_results of bta_hl_main.cc, there is a possible use-after-free due to a race condition. Rated high severity (CVSS 7.5), this vulnerability is remotely exploitable, no authentication required. No vendor patch available.
In the Linux kernel before 4.20.8, kvm_ioctl_create_device in virt/kvm/kvm_main.c mishandles reference counting because of a race condition, leading to a use-after-free. Rated high severity (CVSS 8.1), this vulnerability is remotely exploitable, no authentication required. Public exploit code available.
An issue was discovered in Metinfo 6.x. Rated high severity (CVSS 8.1), this vulnerability is remotely exploitable, no authentication required. Public exploit code available and no vendor patch available.
Debian tmpreaper version 1.6.13+nmu1 has a race condition when doing a (bind) mount via rename() which could result in local privilege escalation. Rated high severity (CVSS 7.0). No vendor patch available.
In PolicyKit (aka polkit) 0.115, the "start time" protection mechanism can be bypassed because fork() is not atomic, and therefore authorization decisions are improperly cached. Rated medium severity (CVSS 6.7).
Elasticsearch Security versions 6.4.0 to 6.4.2 contain an error in the way request headers are applied to requests when using the Active Directory, LDAP, Native, or File realms. Rated medium severity (CVSS 6.5), this vulnerability is remotely exploitable, low attack complexity. No vendor patch available.
In Veraport G3 ALL on MacOS, a race condition when calling the Veraport API allow remote attacker to cause arbitrary file download and execution. Rated high severity (CVSS 8.1), this vulnerability is remotely exploitable, no authentication required. No vendor patch available.
v9fs_wstat in hw/9pfs/9p.c in QEMU allows guest OS users to cause a denial of service (crash) because of a race condition during file renaming. Rated medium severity (CVSS 4.7).
A flaw was found in qemu Media Transfer Protocol (MTP) before version 3.1.0. Rated high severity (CVSS 7.8).
In easelcomm_hw_build_scatterlist, there is a possible out of bounds write due to a race condition. Rated medium severity (CVSS 6.4). No vendor patch available.
The svpn component of the F5 BIG-IP APM client prior to version 7.1.7.2 for Linux and macOS runs as a privileged process and can allow an unprivileged user to get ownership of files owned by root on. Rated high severity (CVSS 7.0). No vendor patch available.
A Race condition vulnerability in unzip_file in admin/import/class-import-settings.php in the Yoast SEO (wordpress-seo) plugin before 9.2.0 for WordPress allows an SEO Manager to perform command. Rated medium severity (CVSS 6.6), this vulnerability is remotely exploitable. Public exploit code available and no vendor patch available.
In the ClearKey CAS descrambler, there is a possible use after free due to a race condition. Rated high severity (CVSS 7.0).
A race in the handling of SharedArrayBuffers in WebAssembly in Google Chrome prior to 65.0.3325.146 allowed a remote attacker to potentially exploit heap corruption via a crafted HTML page. Rated high severity (CVSS 7.5), this vulnerability is remotely exploitable, no authentication required. No vendor patch available.
A race condition in chown_one() of systemd allows an attacker to cause systemd to set arbitrary permissions on arbitrary files. Rated high severity (CVSS 7.0). Public exploit code available.
In the Linux kernel through 4.19, a use-after-free can occur due to a race condition between fanout_add from setsockopt and bind on an AF_PACKET socket. Rated high severity (CVSS 8.1), this vulnerability is remotely exploitable, no authentication required. Public exploit code available and no vendor patch available.
A remote unauthorized disclosure of information vulnerability was identified in HPE Service Governance Framework (SGF) version 4.2, 4.3. Rated medium severity (CVSS 5.9), this vulnerability is remotely exploitable, no authentication required. No vendor patch available.
A vulnerability in the errdisable per VLAN feature of Cisco IOS XE Software could allow an unauthenticated, adjacent attacker to cause the device to crash, leading to a denial of service (DoS). Rated medium severity (CVSS 6.1), this vulnerability is no authentication required. No vendor patch available.
An issue was discovered in the proc_pid_stack function in fs/proc/base.c in the Linux kernel through 4.18.11. Rated medium severity (CVSS 5.5), this vulnerability is low attack complexity.
In some Lenovo IdeaPad consumer notebook models, a race condition in the BIOS flash device locking mechanism is not adequately protected against, potentially allowing an attacker with administrator. Rated medium severity (CVSS 5.9), this vulnerability is remotely exploitable. No vendor patch available.
In all android releases (Android for MSM, Firefox OS for MSM, QRD Android) from CAF using the linux kernel, LUT configuration is passed down to driver from userspace via ioctl. Rated high severity (CVSS 7.0).
Gitolite before 3.6.9 does not (in certain configurations involving @all or a regex) properly restrict access to a Git repository that is in the process of being migrated until the full set of. Rated high severity (CVSS 8.1), this vulnerability is remotely exploitable, low attack complexity.
GEAR Software products that include GEARAspiWDM.sys, 2.2.5.0, allow local users to cause a denial of service (Race Condition and BSoD on Windows) by not checking that user-mode memory is available. Rated medium severity (CVSS 4.7). Public exploit code available and no vendor patch available.
OpenSSH through 7.7 is prone to a user enumeration vulnerability due to not delaying bailout for an invalid authenticating user until after the packet containing the request has been fully parsed,. Rated medium severity (CVSS 5.3), this vulnerability is remotely exploitable, no authentication required, low attack complexity. Public exploit code available.
If an async request was completed by the application at the same time as the container triggered the async timeout, a race condition existed that could result in a user seeing a response intended for. Rated medium severity (CVSS 5.9), this vulnerability is remotely exploitable, no authentication required.
An issue was discovered in the __ns_get_path function in fs/nsfs.c in the Linux kernel before 4.11. Rated high severity (CVSS 7.0).
Due to a race condition in the MDSS MDP driver in all Android releases from CAF using the Linux kernel (Android for MSM, Firefox OS for MSM, QRD Android) before security patch level 2018-07-05, a Use. Rated high severity (CVSS 7.0).
A race condition exists in a driver in all Android releases from CAF using the Linux kernel (Android for MSM, Firefox OS for MSM, QRD Android) before security patch level 2018-05-05 potentially. Rated high severity (CVSS 7.0). No vendor patch available.
Due to a race condition in a camera driver ioctl handler in Android releases from CAF using the linux kernel (Android for MSM, Firefox OS for MSM, QRD Android) before security patch level 2018-06-05,. Rated high severity (CVSS 7.0). No vendor patch available.
Time-of-check to time-of-use (TOCTOU) race condition in org.onosproject.acl (aka the access control application) in ONOS v1.13 and earlier allows attackers to bypass network access control via data. Rated medium severity (CVSS 6.8), this vulnerability is remotely exploitable, no authentication required.
CVE-2018-8025 describes an issue in Apache HBase that affects the optional "Thrift 1" API server when running over HTTP. Rated high severity (CVSS 8.1), this vulnerability is remotely exploitable, no authentication required. No vendor patch available.
An issue was discovered in the Linux kernel through 4.17.2. Rated medium severity (CVSS 6.3).
Symantec Endpoint Protection prior to 14 RU1 MP1 or 12.1 RU6 MP10 may be susceptible to a race condition (or race hazard). Rated medium severity (CVSS 5.3), this vulnerability is remotely exploitable. No vendor patch available.
A race condition in the nginx module in Phusion Passenger 3.x through 5.x before 5.3.2 allows local escalation of privileges when a non-standard passenger_instance_registry_dir with insufficiently. Rated high severity (CVSS 7.0). No vendor patch available.
389-ds-base before versions 1.4.0.10, 1.3.8.3 is vulnerable to a race condition in the way 389-ds-base handles persistent search, resulting in a crash if the server is under load. Rated medium severity (CVSS 5.9), this vulnerability is remotely exploitable, no authentication required.
private_address_check ruby gem before 0.5.0 is vulnerable to a time-of-check time-of-use (TOCTOU) race condition due to the address the socket uses not being checked. Rated low severity (CVSS 3.7), this vulnerability is remotely exploitable, no authentication required.
Due to a race condition in the QTEECOM driver in all Android releases from CAF (Android for MSM, Firefox OS for MSM, QRD Android) using the Linux Kernel, when more than one HLOS client loads the same. Rated high severity (CVSS 7.0).
In the Linux Kernel before version 4.16.11, 4.14.43, 4.9.102, and 4.4.133, multiple race condition errors when handling probe, disconnect, and rebind operations can be exploited to trigger a. Rated high severity (CVSS 7.0).
Quick Facts
- Typical Severity
- MEDIUM
- Category
- web
- Total CVEs
- 2128