Attack ChainAIDerived
Hypothetical attack flow derived from CVE metadata – not a confirmed exploit chain
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AccessGain adjacent-network access to TFTP segment
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DeliveryRequest a TFTP file to seed transfer cache
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ExploitVictim PXE client requests its boot file
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ExecutionStale uninvalidated cache serves attacker content
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ImpactVictim boots attacker-supplied image
Vulnerability Assessment
| Weakness |
CWE
ASVS 5.0
V15 - Secure Coding and Architecture Operation on resource after expiration or release
|
| Exploitation Conditions | Requires dnsmasq to be running with its TFTP server feature enabled (typically for PXE/network boot) - the flaw does not exist when TFTP is not in use. The attacker must be on the adjacent/local network able to issue TFTP requests to the server (AV:A), and exploitation is unauthenticated (PR:N, TFTP has no auth) with no user interaction (UI:N). Key limiting factors: the attack is high-complexity (AC:H) because the attacker cannot control when a later client will request the same file and thus receive the stale cached data; it is not remotely exploitable over the internet; and meaningful impact (malicious boot content) depends on the environment actually using dnsmasq TFTP for PXE provisioning, a non-default, specific deployment mode. |
| Impact | This is a moderate-severity, situational issue rather than a drop-everything emergency, and the signals are largely consistent. The CVSS 3.1 vector (AV:A/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:N, 6.8) correctly frames it as adjacent-network (not internet-routable), high-complexity, and unauthenticated, with high confidentiality and integrity impact but no availability impact - matching CWE-672 (use of a resource after expiration/release: the TFTP transfer cache is not invalidated when a transfer completes). The vuln.today decision label is 'this_month', which aligns with a real-but-not-urgent priority. Exploitation status: no public exploit identified at time of analysis - there is no CISA KEV listing, no POC/exploit reference in the input, and no EPSS score provided, so widespread or automated exploitation is not indicated. The main caveat is that the real-world impact hinges entirely on deployment: the flaw matters only where dnsmasq's TFTP server is enabled, typically for PXE network boot, which is a specific (often datacenter/provisioning) configuration rather than a default. Within such environments the integrity consequence - substituting attacker-chosen boot content - is serious, but AC:H reflects that the attacker cannot control when a later client will request the stale-cached file. No conflicting signals were found; the chief gap is the absence of EPSS/KEV/POC data and no listed fixed version in the provided sources. |
| Exploit ScenarioDerived | On a LAN segment served by a dnsmasq instance with its TFTP server enabled for PXE boot, an attacker requests a TFTP file, leaving its contents in the transfer cache that is never invalidated after the transfer finishes. When a victim machine subsequently PXE-boots and requests its boot file, dnsmasq serves the previously cached data instead of the correct file, allowing attacker-chosen boot content to be delivered to the victim. No public exploit code is identified; the adjacent-network vector and high attack complexity (the attacker cannot control the timing of the later client request) limit opportunistic abuse. |
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Alert meAnalysisAIv1 – Oct 29, 2026
TFTP file substitution in dnsmasq allows an attacker on the local network to make a later client receive stale, previously cached transfer data instead of the file it requested; in PXE network-boot deployments this can substitute attacker-chosen boot content for a victim machine, giving both confidentiality and integrity impact. The flaw only exists when dnsmasq is running with its TFTP server feature enabled (a non-default configuration used for network boot), requires adjacent-network access (AV:A) with no authentication (PR:N) and no user interaction (UI:N), but is rated high complexity (AC:H) because the attacker cannot control when another client will request the same file and pick up the cached response. There is no CISA KEV entry and no public exploit code identified at time of analysis, and the vendor-reported CVSS 3.1 score is 6.8, making this a moderate, situational issue rather than an emergency; Red Hat tracks it for remediation within the current monthly cycle.
RemediationAI
No vendor-released patch was identified in the available data for CVE-2026-93006, so track the Red Hat advisory at https://access.redhat.com/security/cve/CVE-2026-93006 and Bugzilla https://bugzilla.redhat.com/show_bug.cgi?id=2536075 for the dnsmasq errata covering RHEL 6, 7, 8, 9, 10 and the Ceph, OpenShift and OpenStack channels, and apply the updated dnsmasq package as soon as it is published. Because the defect only exists when the TFTP server is in use, the most direct mitigation is to disable it: remove or comment the enable-tftp directive (and any tftp-root setting) from dnsmasq.conf and restart the service, which eliminates the vulnerable code path entirely - the trade-off is that PXE/network boot clients served by that host will no longer boot until an alternative boot server is provided. Where TFTP must stay enabled for provisioning, restrict reachability of the TFTP service to the specific provisioning VLAN or subnet via host firewalls or network ACLs, since TFTP performs no authentication and any adjacent host can otherwise issue requests; the trade-off is tighter change control on boot infrastructure and the risk that legitimate PXE clients outside the permitted segment fail to boot. Environments that do not use dnsmasq for PXE boot should treat disabling TFTP as the primary control rather than waiting on the package update, and operators should not rely on monitoring alone, as a substituted boot image may only be visible as unexpected client behaviour.
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Technical ContextAI · show details
dnsmasq is a lightweight DNS forwarder, DHCP server and TFTP server commonly bundled in Linux distributions and appliances; its TFTP component is typically enabled alongside DHCP to support PXE/network boot of clients. The root cause is classed as CWE-672 (Operation on a Resource after Expiration or Release): dnsmasq keeps a cache of recently used TFTP transfers so repeat requests for the same file can be served efficiently, but that entry is not invalidated when a transfer completes, so the cached content remains usable after it should have been released. A client requesting a file that matches a stale cache entry can therefore be served bytes belonging to an earlier transfer rather than its own requested content. Because TFTP itself has no authentication or session integrity, any host on the adjacent network able to reach the TFTP service can issue requests, and the corruption is only detected by the receiving client. The trigger for the specific cache-reuse path is described only at this level in the available sources; what is confirmed is that the flaw is absent unless the TFTP server feature is in use, and that meaningful integrity impact requires an environment where dnsmasq TFTP actually serves PXE boot content. The Red Hat advisory (access.redhat.com/security/cve/CVE-2026-93006) and Bugzilla entry 2536075 are the primary tracking references.
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Severity by source
AV:A/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:N
TFTP is adjacent-network and unauthenticated (AV:A, PR:N); AC:H because the attacker cannot control when a later client requests the stale-cached file; a victim receives another's data (C:H) and attacker-staged boot content (I:H), with no availability impact.
Primary rating from Vendor (redhat).
CVSS VectorVendor: redhat
DescriptionCVE.org
A flaw was found in dnsmasq. The TFTP server can serve the wrong file contents because a recently used transfer cache is not invalidated when a transfer finishes. An attacker on the local network who can request a TFTP file may cause a later client to receive previously cached data instead of the requested file. In PXE network-boot environments this can substitute attacker-chosen boot content for a victim machine.
Threat Intelligence Overview
How this decision was reached
The engine reads each signal below and applies a fixed list of rules from top to bottom. The first rule that matches sets the recommended action – like a statement, every line is shown.
What every action level means
SSVC AssessmentENISA
Priority Score
Attack Technique
Information disclosure occurs when an application unintentionally exposes sensitive data that aids attackers in reconnaissance or directly compromises security.
Affected Products (CPE)CVE.org
Heap-based buffer overflow in dnsmasq before 2.78 allows remote attackers to cause a denial of service (crash) or execut
Heap-based buffer overflow in dnsmasq before 2.78 allows remote attackers to cause a denial of service (crash) or execut
In dnsmasq before 2.78, if the DNS packet size does not match the expected size, the size parameter in a memset call get
Memory leak in dnsmasq before 2.78, when the --add-mac, --add-cpe-id or --add-subnet option is specified, allows remote
Integer underflow in the add_pseudoheader function in dnsmasq before 2.78 , when the --add-mac, --add-cpe-id or --add-su
Stack-based buffer overflow in dnsmasq before 2.78 allows remote attackers to cause a denial of service (crash) or execu
CRLF injection in the Dnsmasq configuration path of Oray Pugongying X5 Pro 7.6.1 lets a user who already holds administr
dnsmasq before 2.78, when configured as a relay, allows remote attackers to obtain sensitive memory information via vect
Improper bounds checking in Dnsmasq before 2.76 allows an attacker controlled DNS server to send large DNS packets that
The tcp_request function in Dnsmasq before 2.73rc4 does not properly handle the return value of the setup_reply function
Dnsmasq before 2.66test2, when used with certain libvirt configurations, replies to queries from prohibited interfaces,
Heap-based buffer overflow in dnsmasq's DHCPv6 implementation enables local attackers to execute arbitrary code with roo
EUVD-2026-112791
GHSA-fp59-6rfj-9jgw
NVD
CVE.org
EPSS
Exploit-DB