Linux: Concurrent Execution using Shared Resource with Improper Synchronization
CVE-2026-31516 is a high-severity concurrent execution using shared resource with improper synchronization vulnerability in Linux, with a CVSS 3.1 base score of 7.8 out of 10. It can be exploited with local access to the system by an attacker with a low-privileged account, without any action from a user. The record lists versions 56ea2257b83ee29a543f158159e3d1abc1e3e4fe, 8854e9367465d784046362698731c1111e3b39b8, 4e2e77843fef473ef47e322d52436d8308582a96 as the first without the flaw, so updating Linux to one of those releases or later removes the exposure. There is no confirmed exploitation so far. EPSS estimates a 0.1% chance of exploitation within 30 days, which is low compared with other CVEs.
High severity with no evidence of exploitation so far.
What to do
- Update Linux to 56ea2257b83ee29a543f158159e3d1abc1e3e4fe or 8854e9367465d784046362698731c1111e3b39b8 or 4e2e77843fef473ef47e322d52436d8308582a96 or 29fe3a61bcdce398ee3955101c39f89c01a8a77e, whichever matches your release line, or a later version.
- Update Linux Kernel to 6.12.80 or 6.18.21 or 6.19.11, whichever matches your release line, or a later version.
Affected products and versions
| Vendor | Product | Affected versions | Fixed in |
|---|---|---|---|
| Linux | Linux | 880a6fab8f6ba5b5abe59ea68533202ddea1012c up to, but not including, 56ea2257b83ee29a543f158159e3d1abc1e3e4fe; 880a6fab8f6ba5b5abe59ea68533202ddea1012c up to, but not including, 8854e9367465d784046362698731c1111e3b39b8; 880a6fab8f6ba5b5abe59ea68533202ddea1012c up to, but not including, 4e2e77843fef473ef47e322d52436d8308582a96; 880a6fab8f6ba5b5abe59ea68533202ddea1012c up to, but not including, 29fe3a61bcdce398ee3955101c39f89c01a8a77e; 3.18 | 56ea2257b83ee29a543f158159e3d1abc1e3e4fe, 8854e9367465d784046362698731c1111e3b39b8, 4e2e77843fef473ef47e322d52436d8308582a96, 29fe3a61bcdce398ee3955101c39f89c01a8a77e |
| Linux | Linux Kernel | 3.18.1 up to, but not including, 6.12.80; 6.13 up to, but not including, 6.18.21; 6.19 up to, but not including, 6.19.11; 3.18; 7.0 | 6.12.80, 6.18.21, 6.19.11 |
Version data comes from the organisation that assigned the CVE. Confirm against the vendor advisory before deciding you are unaffected.
How the severity score breaks down
- Attack vector
- LocalThe attacker needs local access or must trick a user into running something.
- Attack complexity
- LowNo special conditions are needed; the attack works reliably.
- Privileges required
- LowA basic user account is enough.
- User interaction
- NoneNo action by a victim is required.
- Scope
- UnchangedImpact stays within the vulnerable component.
- Confidentiality
- HighAll data handled by the component can be read.
- Integrity
- HighData or code can be modified at will.
- Availability
- HighThe component can be taken down completely.
Vector: CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H. Scored by CNA.
Official description
In the Linux kernel, the following vulnerability has been resolved: xfrm: prevent policy_hthresh.work from racing with netns teardown A XFRM_MSG_NEWSPDINFO request can queue the per-net work item policy_hthresh.work onto the system workqueue. The queued callback, xfrm_hash_rebuild(), retrieves the enclosing struct net via container_of(). If the net namespace is torn down before that work runs, the associated struct net may already have been freed, and xfrm_hash_rebuild() may then dereference stale memory. xfrm_policy_fini() already flushes policy_hash_work during teardown, but it does not synchronize policy_hthresh.work. Synchronize policy_hthresh.work in xfrm_policy_fini() as well, so the queued work cannot outlive the net namespace teardown and access a freed struct net.
Source: the CVE record as published by its numbering authority, via NVD and CVE.org.
The underlying weakness: Concurrent Execution using Shared Resource with Improper Synchronization
The product contains a concurrent code sequence that requires temporary, exclusive access to a shared resource, but a timing window exists in which the shared resource can be modified by another code sequence operating concurrently.
How developers prevent this class of flaw
- In languages that support it, use synchronization primitives. Only wrap these around critical code to minimize the impact on performance.
- Use thread-safe capabilities such as the data access abstraction in Spring.
- Minimize the usage of shared resources in order to remove as much complexity as possible from the control flow and to reduce the likelihood of unexpected conditions occurring. Additionally, this will minimize the amount of synchronization necessary and may even help to reduce the likelihood of a denial of service where an attacker may be able to repeatedly trigger a critical section (CWE-400).
Timeline
- CVE record published.
- CISA published its SSVC assessment (exploitation: none, automatable: no, technical impact: total).
- Record last changed materially (score, affected products, status or references).
References
Patches and release notes
Recent Concurrent Execution using Shared Resource with Improper Synchronization vulnerabilities
- 7.8 High severity
- 8.2 High severity
- 8.7 High severity
- 8.1 High severity
- 7.0 High severity
- 7.8 High severity
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