Severity by source
CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X
Network vector, no privileges or interaction required for anonymous daemons; scope unchanged, pure availability impact with no confidentiality or integrity effect.
AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
Primary rating from Vendor (VulnCheck).
CVSS VectorVendor: VulnCheck
Lifecycle Timeline
3DescriptionCVE.org
rsync 3.4.2 before 3.5.0 contains a denial of service vulnerability that allows a remote sender to exhaust system resources by specifying the --zt short alias for --compress-threads, which bypasses the refuse options directive's string matching on long option names. Attackers can specify --zt=N with a large value to spawn an unbounded number of Zstandard worker threads on the receiver, exhausting available thread and memory resources.
AnalysisAI
Denial of service in rsync's receiver process allows a remote, unauthenticated sender to exhaust thread and memory resources by specifying the --zt short alias for --compress-threads, directly bypassing daemon-side refuse options directives that match only against long option names. Affected versions span 3.4.2 through 3.4.x prior to 3.5.0; the bypass is most damaging to operators who explicitly configured refuse options to block --compress-threads, since they believed a mitigation was in place. No public exploit has been identified at time of analysis and no CISA KEV listing exists, but the CVSS 4.0 score of 8.7 accurately reflects low-complexity, unauthenticated network exploitation with high availability impact.
Technical ContextAI
rsync is a widely deployed file synchronization utility that operates either as a standalone daemon (rsyncd) or over SSH. The vulnerability is rooted in CWE-770 (Allocation of Resources Without Limits or Throttling): when --zt=N is passed, the receiver spawns exactly N Zstandard (zstd) compression worker threads without enforcing any ceiling, consuming thread handles and heap memory proportional to N. The rsync daemon's refuse options security directive is designed to let administrators reject client-specified options by name, but its implementation performs string comparison only against full long option names such as --compress-threads, not registered short aliases such as --zt. This is a security control bypass rather than a pure implementation bug: the resource allocation itself is intentional, but the gatekeeping mechanism is incomplete. The CPE string cpe:2.3:a:rsyncproject:rsync:*:*:*:*:*:*:*:* scopes the affected product to the rsyncproject's canonical rsync implementation across all platforms.
RemediationAI
Upgrade rsync to version 3.5.0, designated by the upstream project as a major security release and available at https://github.com/RsyncProject/rsync/releases/tag/v3.5.0. Where immediate upgrade is not feasible, administrators should manually append --zt to the refuse options list in rsyncd.conf as a compensating control; note that this approach requires identifying and blocking every registered short alias for resource-intensive options, and may be incomplete if additional undiscovered aliases exist - it is a partial mitigation, not equivalent to patching. Restricting rsync daemon access to trusted source IP ranges using rsyncd.conf hosts allow directives or an upstream firewall rule is an independent layer that significantly reduces the attack surface, with the trade-off of blocking legitimate clients from unrestricted ranges. Disabling Zstandard compression support at the rsyncd module level, if the deployment does not require zstd, eliminates the thread-spawning vector entirely. The vendor advisory at https://github.com/RsyncProject/rsync/security/advisories/GHSA-rjvj-qgqg-cvx9 and the VulnCheck advisory at https://www.vulncheck.com/advisories/rsync-dos-via-zt-zstandard-compression-thread-exhaustion provide additional operator guidance.
A flaw was found in rsync which could be triggered when rsync compares file checksums. Rated high severity (CVSS 7.5), t
A heap-based buffer overflow flaw was found in the rsync daemon. Rated critical severity (CVSS 9.8), this vulnerability
rsync 3.1.1 allows remote attackers to write to arbitrary files via a symlink attack on a file in the synchronization pa
Server-to-client path traversal in rsync lets a malicious or compromised rsync server write files outside the client's i
An issue was discovered in rsync before 3.2.5 that allows malicious remote servers to write arbitrary files inside the d
The check_secret function in authenticate.c in rsync 3.1.0 and earlier allows remote attackers to cause a denial of serv
A flaw was found in rsync. Rated medium severity (CVSS 6.1), this vulnerability is remotely exploitable, no authenticati
The receive_xattr function in xattrs.c in rsync 3.1.2 and 3.1.3-development does not check for a trailing '\0' character
The daemon in rsync 3.1.2, and 3.1.3-development before 2017-12-03, does not check for fnamecmp filenames in the daemon_
rsync 3.1.3-development before 2017-10-24 mishandles archaic checksums, which makes it easier for remote attackers to by
Arbitrary command execution in rsync before 3.5.0 arises from multiple unsanitized code paths - the RSYNC_CONNECT_PROG e
Arbitrary file write in rsync 2.3.3 through 3.4.4 lets a malicious sender escape a daemon module's root by abusing symli
Same technique Denial Of Service
View allVendor StatusVendor
SUSE
Severity: Important| Product | Status |
|---|---|
| SUSE Linux Enterprise High Performance Computing 15 SP4-ESPOS | Affected |
| SUSE Linux Enterprise High Performance Computing 15 SP4-LTSS | Affected |
| SUSE Linux Enterprise High Performance Computing 15 SP5-ESPOS | Affected |
| SUSE Linux Enterprise High Performance Computing 15 SP5-LTSS | Affected |
| SUSE Linux Enterprise Micro 5.3 | Affected |
| SUSE Linux Enterprise Micro 5.4 | Affected |
| SUSE Linux Enterprise Micro 5.5 | Affected |
| SUSE Linux Enterprise Module for Basesystem 15 SP7 | Affected |
| SUSE Linux Enterprise Server 15 SP7 | Affected |
| SUSE Linux Enterprise Desktop 15 SP7 | Affected |
| SUSE Linux Enterprise Server for SAP Applications 15 SP7 | Affected |
| SUSE Linux Enterprise High Performance Computing 15 SP7 | Affected |
| SUSE Linux Enterprise Server 15 SP4-LTSS | Affected |
| SUSE Linux Enterprise Server 15 SP4-LTSS | Affected |
| SUSE Linux Enterprise Server 15 SP5-LTSS | Affected |
| SUSE Linux Enterprise Server 15 SP5-LTSS | Affected |
| SUSE Linux Enterprise Server 15 SP6-LTSS | Affected |
| SUSE Linux Enterprise Server 15 SP6-LTSS | Affected |
| SUSE Linux Enterprise Server for SAP Applications 15 SP4 | Affected |
| SUSE Linux Enterprise Server for SAP Applications 15 SP5 | Affected |
| SUSE Linux Enterprise Server for SAP Applications 15 SP6 | Affected |
| SUSE Manager Proxy LTS 4.3 | Affected |
| SUSE Manager Retail Branch Server LTS 4.3 | Affected |
| SUSE Manager Server LTS 4.3 | Affected |
| SUSE Linux Enterprise Desktop 15 SP7 | Affected |
| SUSE Linux Enterprise High Performance Computing 12 | Not-Affected |
| SUSE Linux Enterprise High Performance Computing 15 SP7 | Affected |
| SUSE Linux Enterprise Micro 5.3 | Affected |
| SUSE Linux Enterprise Micro 5.4 | Affected |
| SUSE Linux Enterprise Micro 5.5 | Affected |
| SUSE Linux Enterprise Module for Basesystem 15 SP7 | Affected |
| SUSE Linux Enterprise Server 15 SP7 | Affected |
| SUSE Linux Enterprise Server 16.0 | Affected |
| SUSE Linux Enterprise Server 16.1 | Affected |
| SUSE Linux Enterprise Server for SAP Applications 15 SP7 | Affected |
| SUSE Linux Enterprise Server for SAP applications 16.0 | Affected |
| SUSE Linux Enterprise Server for SAP applications 16.1 | Affected |
| SUSE Linux Micro 6.0 | Not-Affected |
| SUSE Linux Micro 6.1 | Not-Affected |
| SUSE Linux Micro 6.2 | Affected |
| openSUSE Leap 16.0 | Not-Affected |
| SUSE Linux Enterprise High Performance Computing 12 SP5 | Not-Affected |
| SUSE Linux Enterprise High Performance Computing 15 SP4-LTSS | Affected |
| SUSE Linux Enterprise High Performance Computing 15 SP5 | Not-Affected |
| SUSE Linux Enterprise High Performance Computing 15 SP5-LTSS | Affected |
| SUSE Linux Enterprise Module for Basesystem 15 SP4 | Not-Affected |
| SUSE Linux Enterprise Module for Basesystem 15 SP5 | Not-Affected |
| SUSE Linux Enterprise Module for Basesystem 15 SP6 | Not-Affected |
| SUSE Linux Enterprise Server 12 SP5 | Not-Affected |
| SUSE Linux Enterprise Server 12 SP5-LTSS | Not-Affected |
| SUSE Linux Enterprise Server 12 SP5-LTSS Extended Security | Not-Affected |
| SUSE Linux Enterprise Server 15 SP4 | Not-Affected |
| SUSE Linux Enterprise Server 15 SP4-LTSS | Affected |
| SUSE Linux Enterprise Server 15 SP5 | Not-Affected |
| SUSE Linux Enterprise Server 15 SP5-LTSS | Affected |
| SUSE Linux Enterprise Server 15 SP6 | Not-Affected |
| SUSE Linux Enterprise Server 15 SP6-LTSS | Affected |
| SUSE Linux Enterprise Server LTSS Extended Security 12 SP5 | Not-Affected |
| SUSE Linux Enterprise Server for SAP Applications 15 SP4 | Affected |
| SUSE Linux Enterprise Server for SAP Applications 15 SP5 | Affected |
| SUSE Linux Enterprise Server for SAP Applications 15 SP6 | Affected |
| SUSE Manager Proxy 4.3 | Not-Affected |
| SUSE Manager Proxy LTS 4.3 | Affected |
| SUSE Manager Retail Branch Server 4.3 | Not-Affected |
| SUSE Manager Retail Branch Server LTS 4.3 | Affected |
| SUSE Manager Server 4.3 | Not-Affected |
| SUSE Manager Server LTS 4.3 | Affected |
| SUSE CaaS Platform 3.0 | Not-Affected |
| SUSE CaaS Platform 4.0 | Not-Affected |
| SUSE Enterprise Storage 6 | Not-Affected |
| SUSE Enterprise Storage 7 | Not-Affected |
| SUSE Enterprise Storage 7.1 | Not-Affected |
| SUSE Linux Enterprise Desktop 12 | Not-Affected |
| SUSE Linux Enterprise Desktop 12 SP1 | Not-Affected |
| SUSE Linux Enterprise Desktop 12 SP2 | Not-Affected |
| SUSE Linux Enterprise Desktop 12 SP3 | Not-Affected |
| SUSE Linux Enterprise Desktop 12 SP4 | Not-Affected |
| SUSE Linux Enterprise Desktop 15 | Not-Affected |
| SUSE Linux Enterprise Desktop 15 SP1 | Not-Affected |
| SUSE Linux Enterprise Desktop 15 SP2 | Not-Affected |
| SUSE Linux Enterprise Desktop 15 SP3 | Not-Affected |
| SUSE Linux Enterprise Desktop 15 SP4 | Not-Affected |
| SUSE Linux Enterprise Desktop 15 SP5 | Not-Affected |
| SUSE Linux Enterprise Desktop 15 SP6 | Not-Affected |
| SUSE Linux Enterprise High Performance Computing 12 SP1 | Not-Affected |
| SUSE Linux Enterprise High Performance Computing 12 SP2 | Not-Affected |
| SUSE Linux Enterprise High Performance Computing 12 SP3 | Not-Affected |
| SUSE Linux Enterprise High Performance Computing 12 SP4 | Not-Affected |
| SUSE Linux Enterprise High Performance Computing 15 | Not-Affected |
| SUSE Linux Enterprise High Performance Computing 15 SP1 | Not-Affected |
| SUSE Linux Enterprise High Performance Computing 15 SP1-ESPOS | Not-Affected |
| SUSE Linux Enterprise High Performance Computing 15 SP1-LTSS | Not-Affected |
| SUSE Linux Enterprise High Performance Computing 15 SP2 | Not-Affected |
| SUSE Linux Enterprise High Performance Computing 15 SP2-ESPOS | Not-Affected |
| SUSE Linux Enterprise High Performance Computing 15 SP2-LTSS | Not-Affected |
| SUSE Linux Enterprise High Performance Computing 15 SP3 | Not-Affected |
| SUSE Linux Enterprise High Performance Computing 15 SP3-ESPOS | Not-Affected |
| SUSE Linux Enterprise High Performance Computing 15 SP3-LTSS | Not-Affected |
| SUSE Linux Enterprise High Performance Computing 15 SP4 | Not-Affected |
| SUSE Linux Enterprise High Performance Computing 15 SP4-ESPOS | Affected |
| SUSE Linux Enterprise High Performance Computing 15 SP5-ESPOS | Affected |
| SUSE Linux Enterprise High Performance Computing 15 SP6 | Not-Affected |
| SUSE Linux Enterprise High Performance Computing 15-ESPOS | Not-Affected |
| SUSE Linux Enterprise High Performance Computing 15-LTSS | Not-Affected |
| SUSE Linux Enterprise Micro 5.0 | Not-Affected |
| SUSE Linux Enterprise Micro 5.1 | Not-Affected |
| SUSE Linux Enterprise Micro 5.2 | Not-Affected |
| SUSE Linux Enterprise Module for Basesystem 15 | Not-Affected |
| SUSE Linux Enterprise Module for Basesystem 15 SP1 | Not-Affected |
| SUSE Linux Enterprise Module for Basesystem 15 SP2 | Not-Affected |
| SUSE Linux Enterprise Module for Basesystem 15 SP3 | Not-Affected |
| SUSE Linux Enterprise Point of Sale 12 SP2-CLIENT | Not-Affected |
| SUSE Linux Enterprise Real Time 15 SP2 | Not-Affected |
| SUSE Linux Enterprise Real Time 15 SP3 | Not-Affected |
| SUSE Linux Enterprise Real Time 15 SP4 | Not-Affected |
| SUSE Linux Enterprise Server 12 | Not-Affected |
| SUSE Linux Enterprise Server 12 SP1 | Not-Affected |
| SUSE Linux Enterprise Server 12 SP1-LTSS | Not-Affected |
| SUSE Linux Enterprise Server 12 SP2 | Not-Affected |
| SUSE Linux Enterprise Server 12 SP2-BCL | Not-Affected |
| SUSE Linux Enterprise Server 12 SP2-ESPOS | Not-Affected |
| SUSE Linux Enterprise Server 12 SP2-LTSS | Not-Affected |
| SUSE Linux Enterprise Server 12 SP3 | Not-Affected |
| SUSE Linux Enterprise Server 12 SP3-BCL | Not-Affected |
| SUSE Linux Enterprise Server 12 SP3-ESPOS | Not-Affected |
| SUSE Linux Enterprise Server 12 SP3-LTSS | Not-Affected |
| SUSE Linux Enterprise Server 12 SP4 | Not-Affected |
| SUSE Linux Enterprise Server 12 SP4-ESPOS | Not-Affected |
| SUSE Linux Enterprise Server 12 SP4-LTSS | Not-Affected |
| SUSE Linux Enterprise Server 12-LTSS | Not-Affected |
| SUSE Linux Enterprise Server 15 | Not-Affected |
| SUSE Linux Enterprise Server 15 SP1 | Not-Affected |
| SUSE Linux Enterprise Server 15 SP1-BCL | Not-Affected |
| SUSE Linux Enterprise Server 15 SP1-LTSS | Not-Affected |
| SUSE Linux Enterprise Server 15 SP2 | Not-Affected |
| SUSE Linux Enterprise Server 15 SP2-BCL | Not-Affected |
| SUSE Linux Enterprise Server 15 SP2-LTSS | Not-Affected |
| SUSE Linux Enterprise Server 15 SP3 | Not-Affected |
| SUSE Linux Enterprise Server 15 SP3-BCL | Not-Affected |
| SUSE Linux Enterprise Server 15 SP3-LTSS | Not-Affected |
| SUSE Linux Enterprise Server 15-LTSS | Not-Affected |
| SUSE Linux Enterprise Server for Raspberry Pi 12 SP2 | Not-Affected |
| SUSE Linux Enterprise Server for SAP Applications 12 SP1 | Not-Affected |
| SUSE Linux Enterprise Server for SAP Applications 12 SP2 | Not-Affected |
| SUSE Linux Enterprise Server for SAP Applications 12 SP3 | Not-Affected |
| SUSE Linux Enterprise Server for SAP Applications 12 SP4 | Not-Affected |
| SUSE Linux Enterprise Server for SAP Applications 15 | Not-Affected |
| SUSE Linux Enterprise Server for SAP Applications 15 SP1 | Not-Affected |
| SUSE Linux Enterprise Server for SAP Applications 15 SP2 | Not-Affected |
| SUSE Linux Enterprise Server for SAP Applications 15 SP3 | Not-Affected |
| SUSE Manager Proxy 4.0 | Not-Affected |
| SUSE Manager Proxy 4.1 | Not-Affected |
| SUSE Manager Proxy 4.2 | Not-Affected |
| SUSE Manager Retail Branch Server 4.0 | Not-Affected |
| SUSE Manager Retail Branch Server 4.1 | Not-Affected |
| SUSE Manager Retail Branch Server 4.2 | Not-Affected |
| SUSE Manager Server 4.0 | Not-Affected |
| SUSE Manager Server 4.1 | Not-Affected |
| SUSE Manager Server 4.2 | Not-Affected |
| SUSE OpenStack Cloud 7 | Not-Affected |
| SUSE OpenStack Cloud 8 | Not-Affected |
| SUSE OpenStack Cloud 9 | Not-Affected |
| SUSE OpenStack Cloud Crowbar 8 | Not-Affected |
| SUSE OpenStack Cloud Crowbar 9 | Not-Affected |
| openSUSE Leap 15.3 | Not-Affected |
| openSUSE Leap 15.4 | Not-Affected |
| openSUSE Leap 15.5 | Not-Affected |
| openSUSE Leap 15.6 | Not-Affected |
| openSUSE Leap Micro 5.2 | Not-Affected |
| openSUSE Leap Micro 5.3 | Not-Affected |
| openSUSE Leap Micro 5.4 | Not-Affected |
| openSUSE Leap Micro 5.5 | Not-Affected |
| bci/kiwi kiwi-templates-Minimal kiwi-templates-Minimal-Cloud-sap kiwi-templates-Minimal-MS-HyperV-sap kiwi-templates-Minimal-VMware-sap kiwi-templates-Minimal-kvm-and-xen-sap rancher/elemental-builder-image/5.3 rancher/elemental-teal-rt/5.3 rancher/elemental-teal-rt/5.4 rancher/elemental-teal/5.3 rancher/elemental-teal/5.4 rancher/seedimage-builder suse/hpc/warewulf4-x86_64/sle-hpc-node suse/manager/5.0/x86_64/server suse/multi-linux-manager/5.1/x86_64/server suse/multi-linux-manager/5.2/x86_64/server suse/sle-micro-rancher/5.2 suse/sle-micro-rancher/5.3 suse/sle-micro-rancher/5.4 suse/sle-micro/5.5 suse/sle-micro/base-5.5 suse/sle-micro/kvm-5.5 suse/sle-micro/rt-5.5 | Not-Affected |
| suse/sles-16.1-kubevirt-minimal | Affected |
Share
External POC / Exploit Code
Leaving vuln.today
EUVD-2026-58049