EUVD-2026-39220
GHSA-7m9q-85qj-rc4g
Severity by source
AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H
Race condition requires concurrent timing (AC:H); local low-privilege access needed; no confidentiality or integrity impact, only availability.
Primary rating from NVD.
CVSS VectorNVD
CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H
Lifecycle Timeline
5DescriptionNVD
In the Linux kernel, the following vulnerability has been resolved:
netfilter: synproxy: add mutex to guard hook reference counting
As the synproxy infrastructure register netfilter hooks on-demand when a user adds the first iptables target or nftables expression, if done concurrently they can race each other.
Introduce a mutex to serialize the refcount control blocks access from both frontends. While a per namespace mutex might be more efficient, it is not needed for target/expression like SYNPROXY.
AnalysisAI
Denial-of-service via race condition in the Linux kernel's netfilter synproxy subsystem allows a local low-privileged user to crash the system by triggering concurrent netfilter hook registration. The synproxy infrastructure registers hooks on-demand when iptables targets or nftables expressions are added; without serialization, concurrent additions race on the reference count control blocks, corrupting kernel state. …
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Attack ChainAIDerived
Hypothetical attack flow derived from CVE metadata
Vulnerability AssessmentAI
| Exploitation | Exploitation requires a local user account with the ability to manipulate netfilter rules - specifically, adding iptables SYNPROXY targets or nftables SYNPROXY expressions concurrently. … Additional conditions and limiting factors are described in the full assessment. |
| Risk Assessment | The CVSS 3.1 base score of 5.5 (AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H) accurately reflects a local, low-privilege, availability-only impact, consistent with the description. … Full risk analysis with EPSS, KEV, and SSVC signal comparison available after sign-in. |
| Exploit Scenario | An attacker with a local low-privileged shell on a vulnerable Linux system (kernel 5.3 to pre-patch) spawns multiple concurrent processes each adding a SYNPROXY iptables target or nftables expression in a network namespace they control. The racing threads simultaneously enter the on-demand hook registration path without serialization, corrupting the synproxy reference count control block. … |
| Remediation | Upgrade the Linux kernel to a patched stable version: 5.10.259, 5.15.210, 6.1.176, 6.6.143, 6.12.94, 6.18.36, 7.0.13, or 7.1 (final). … Detailed patch versions, workarounds, and compensating controls in full report. |
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