Linux: Concurrent Execution using Shared Resource with Improper Synchronization
CVE-2026-43239 is a high-severity concurrent execution using shared resource with improper synchronization vulnerability in Linux, with a CVSS 3.1 base score of 8.8 out of 10. It can be exploited remotely over the network by an unauthenticated attacker, but only if a user takes part, for example by opening a link or file. The record lists versions de3c1653510d566a245cc54ac4bb9e50ebc5faa8, 93e8e3ee165ae4609a1222b516b573837103d2c3, ab6564f416a6eaf1199200b6100952407b438f7d 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 0.29% 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 de3c1653510d566a245cc54ac4bb9e50ebc5faa8 or 93e8e3ee165ae4609a1222b516b573837103d2c3 or ab6564f416a6eaf1199200b6100952407b438f7d or 6287eefaf21ec805d42f941bd368018cf397a7f5, whichever matches your release line, or a later version.
- Update Linux Kernel to 6.6.128 or 6.12.75 or 6.18.16 or 6.19.6, whichever matches your release line, or a later version.
- Until you can update, restrict network access to the affected service so it is not reachable from untrusted networks.
- Because the attack needs a user to take part, warn users about unexpected links and files related to this product until it is patched.
Affected products and versions
| Vendor | Product | Affected versions | Fixed in |
|---|---|---|---|
| Linux | Linux | aa45dadd34e44fcd6a9df4b395bee5b5633b4cec up to, but not including, de3c1653510d566a245cc54ac4bb9e50ebc5faa8; aa45dadd34e44fcd6a9df4b395bee5b5633b4cec up to, but not including, 93e8e3ee165ae4609a1222b516b573837103d2c3; aa45dadd34e44fcd6a9df4b395bee5b5633b4cec up to, but not including, ab6564f416a6eaf1199200b6100952407b438f7d; aa45dadd34e44fcd6a9df4b395bee5b5633b4cec up to, but not including, 6287eefaf21ec805d42f941bd368018cf397a7f5; aa45dadd34e44fcd6a9df4b395bee5b5633b4cec up to, but not including, 76cc4faba0343c6db945b8dc75425b33d633e1b8; aa45dadd34e44fcd6a9df4b395bee5b5633b4cec up to, but not including, c3c06e42e1527716c54f3ad2ced6a034b5f3a489; 5.19 | de3c1653510d566a245cc54ac4bb9e50ebc5faa8, 93e8e3ee165ae4609a1222b516b573837103d2c3, ab6564f416a6eaf1199200b6100952407b438f7d, 6287eefaf21ec805d42f941bd368018cf397a7f5, 76cc4faba0343c6db945b8dc75425b33d633e1b8, c3c06e42e1527716c54f3ad2ced6a034b5f3a489 |
| Linux | Linux Kernel | 5.19.1 up to, but not including, 6.6.128; 6.7 up to, but not including, 6.12.75; 6.13 up to, but not including, 6.18.16; 6.19 up to, but not including, 6.19.6; 5.19 | 6.6.128, 6.12.75, 6.18.16, 6.19.6 |
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
- NetworkCan be exploited remotely over a network, including the internet.
- Attack complexity
- LowNo special conditions are needed; the attack works reliably.
- Privileges required
- NoneNo account or login is needed.
- User interaction
- RequiredA user must take an action such as opening a file or link.
- 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:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H. Scored by CNA.
Official description
In the Linux kernel, the following vulnerability has been resolved: smb: client: prevent races in ->query_interfaces() It was possible for two query interface works to be concurrently trying to update the interfaces. Prevent this by checking and updating iface_last_update under iface_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).
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/6287eefaf21ec805d42f941bd368018cf397a7f5
- git.kernel.org/stable/c/76cc4faba0343c6db945b8dc75425b33d633e1b8
- git.kernel.org/stable/c/93e8e3ee165ae4609a1222b516b573837103d2c3
- git.kernel.org/stable/c/ab6564f416a6eaf1199200b6100952407b438f7d
- git.kernel.org/stable/c/c3c06e42e1527716c54f3ad2ced6a034b5f3a489
Other references
Recent Concurrent Execution using Shared Resource with Improper Synchronization vulnerabilities
- 7.5 High severity
- 7.8 High severity
- 7.5 High severity
- 9.8 Critical severity
- 7.8 High severity
- 7.8 High severity
Spotted an error? Tell us.