Linux: Concurrent Execution using Shared Resource with Improper Synchronization
CVE-2026-43366 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 a7b33671e418fca507feebd1d56e7f4952a4b25c, 439a6728ec4641ffad1ca796622c19bc525e570f, f3fb54e7a8b4aadcc2836ee463eec8c88709b8aa 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 0.13% 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 a7b33671e418fca507feebd1d56e7f4952a4b25c or 439a6728ec4641ffad1ca796622c19bc525e570f or f3fb54e7a8b4aadcc2836ee463eec8c88709b8aa or 50ad880db3013c6fee0ef13781762a39e2e7ef83, whichever matches your release line, or a later version.
- Update Linux Kernel to 6.1.167 or 6.6.130 or 6.12.78 or 6.18.19, whichever matches your release line, or a later version.
Affected products and versions
| Vendor | Product | Affected versions | Fixed in |
|---|---|---|---|
| Linux | Linux | c7fb19428d67dd0a2a78a4f237af01d39c78dc5a up to, but not including, a7b33671e418fca507feebd1d56e7f4952a4b25c; c7fb19428d67dd0a2a78a4f237af01d39c78dc5a up to, but not including, 439a6728ec4641ffad1ca796622c19bc525e570f; c7fb19428d67dd0a2a78a4f237af01d39c78dc5a up to, but not including, f3fb54e7a8b4aadcc2836ee463eec8c88709b8aa; c7fb19428d67dd0a2a78a4f237af01d39c78dc5a up to, but not including, 50ad880db3013c6fee0ef13781762a39e2e7ef83; c7fb19428d67dd0a2a78a4f237af01d39c78dc5a up to, but not including, 97b57f69fee1b61b41acbf37e7720cac9d389fa4; c7fb19428d67dd0a2a78a4f237af01d39c78dc5a up to, but not including, c2c185be5c85d37215397c8e8781abf0a69bec1f; 5.19 | a7b33671e418fca507feebd1d56e7f4952a4b25c, 439a6728ec4641ffad1ca796622c19bc525e570f, f3fb54e7a8b4aadcc2836ee463eec8c88709b8aa, 50ad880db3013c6fee0ef13781762a39e2e7ef83, 97b57f69fee1b61b41acbf37e7720cac9d389fa4, c2c185be5c85d37215397c8e8781abf0a69bec1f |
| Linux | Linux Kernel | 5.19 up to, but not including, 6.1.167; 6.2 up to, but not including, 6.6.130; 6.7 up to, but not including, 6.12.78; 6.13 up to, but not including, 6.18.19; 6.19 up to, but not including, 6.19.9; 7.0 | 6.1.167, 6.6.130, 6.12.78, 6.18.19, 6.19.9 |
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: io_uring/kbuf: check if target buffer list is still legacy on recycle There's a gap between when the buffer was grabbed and when it potentially gets recycled, where if the list is empty, someone could've upgraded it to a ring provided type. This can happen if the request is forced via io-wq. The legacy recycling is missing checking if the buffer_list still exists, and if it's of the correct type. Add those checks.
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
- git.kernel.org/stable/c/439a6728ec4641ffad1ca796622c19bc525e570f
- git.kernel.org/stable/c/50ad880db3013c6fee0ef13781762a39e2e7ef83
- git.kernel.org/stable/c/97b57f69fee1b61b41acbf37e7720cac9d389fa4
- git.kernel.org/stable/c/a7b33671e418fca507feebd1d56e7f4952a4b25c
- git.kernel.org/stable/c/c2c185be5c85d37215397c8e8781abf0a69bec1f
- git.kernel.org/stable/c/f3fb54e7a8b4aadcc2836ee463eec8c88709b8aa
Recent Concurrent Execution using Shared Resource with Improper Synchronization vulnerabilities
- 7.8 High severity
- 7.5 High severity
- 8.8 High severity
- 7.8 High severity
- 7.5 High severity
- 9.8 Critical severity
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