CyberSecBulletin
CVE-2026-53265NVD status: Modified

Linux: Concurrent Execution using Shared Resource with Improper Synchronization

Published Updated By the CyberSecBulletin desk

CVE-2026-53265 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 c242c7af2aecf0b538b8623bdb86b8b441da38d9, 13da856c86fb8c2ccab95034fd77da1bb2c2a17c, d886945fcb0f8c9dc6b39928d7a96c95c587346c 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.

Next patch cycle

High severity with no evidence of exploitation so far.

What to do

  1. Update Linux to c242c7af2aecf0b538b8623bdb86b8b441da38d9 or 13da856c86fb8c2ccab95034fd77da1bb2c2a17c or d886945fcb0f8c9dc6b39928d7a96c95c587346c or b4892561552d671bd8c4da5ebb70e9fbb1ec446e, whichever matches your release line, or a later version.
  2. Update Linux Kernel to 6.6.143 or 6.12.94 or 6.18.36 or 7.0.13, whichever matches your release line, or a later version.

Affected products and versions

VendorProductAffected versionsFixed in
LinuxLinux4991b5a08751e2e82488fb93ae08849b6aea10d9 up to, but not including, c242c7af2aecf0b538b8623bdb86b8b441da38d9; 1b2bec4a7dcf5f00b7a1cbeeec8997841d783513 up to, but not including, 13da856c86fb8c2ccab95034fd77da1bb2c2a17c; 9a5fdfb9e57ec3a8ad2b8fce5e5ffa42d53b130e up to, but not including, d886945fcb0f8c9dc6b39928d7a96c95c587346c; ac5ee99443891bdb161f5539606a66a1b5e72542 up to, but not including, b4892561552d671bd8c4da5ebb70e9fbb1ec446e; 93627a29d4b66d4a2def938dfb8610cc80ae454b up to, but not including, 03ffe1112ed88bb3a9bd0b971549bf4d64bfc59a; c348ae47d8e65f06429fa41adce9ad986b696766 up to, but not including, 42ff6774ecd9d7f70d599cb71ff64373a1da4948; 2b62d0611c9af14a16bddf22df2612b4f40eb5a1 up to, but not including, c57570fba24016ec25ec046ab44db39143fb7a64; 2d1f7b65f5deedd2e6b09fdc6ea27f8375f24b45 up to, but not including, d3f0a606b9f278ece8a0df626ded9c4044071235; and 7 more rangesc242c7af2aecf0b538b8623bdb86b8b441da38d9, 13da856c86fb8c2ccab95034fd77da1bb2c2a17c, d886945fcb0f8c9dc6b39928d7a96c95c587346c, b4892561552d671bd8c4da5ebb70e9fbb1ec446e, 03ffe1112ed88bb3a9bd0b971549bf4d64bfc59a, 42ff6774ecd9d7f70d599cb71ff64373a1da4948
SiemensSIMATIC S7-1500 TM MFP - GNU/Linux subsystemall versionsNot stated
LinuxLinux Kernel6.6.141 up to, but not including, 6.6.143; 6.12.91 up to, but not including, 6.12.94; 6.18.33 up to, but not including, 6.18.36; 7.0.10 up to, but not including, 7.0.13; 5.10.258; 5.15.209; 6.1.175; 7.16.6.143, 6.12.94, 6.18.36, 7.0.13

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: dm cache policy smq: check allocation under invalidate lock commit 2d1f7b65f5de ("dm cache policy smq: fix missing locks in invalidating cache blocks") added mq->lock around the destructive part of smq_invalidate_mapping(), but left the e->allocated check outside the critical section. That leaves a check-then-act race. Two concurrent invalidators can both observe e->allocated as true before either of them takes mq->lock. The first invalidator that acquires the lock removes the entry from the queues and hash table and then calls free_entry(), which clears e->allocated and puts the entry back on the free list. The second invalidator can then acquire mq->lock and continue with the stale result of the unlocked check. This can corrupt the SMQ queues or hash table by deleting an entry that is no longer on those structures. It can also hit the allocation check in free_entry() when the same entry is freed again. Move the allocation check under mq->lock so the predicate and the destructive operations are serialized by the same lock.

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).

More Concurrent Execution using Shared Resource with Improper Synchronization vulnerabilities (CWE-362)

Timeline

  1. CVE record published.
  2. CISA published its SSVC assessment (exploitation: none, automatable: no, technical impact: total).
  3. Record last changed materially (score, affected products, status or references).

References

Recent Concurrent Execution using Shared Resource with Improper Synchronization vulnerabilities

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