Linux: Concurrent Execution using Shared Resource with Improper Synchronization
CVE-2026-31673 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 e7339db13b9ddb63417b12da55fd6191e59f7442, 4f6a8f10182c3a9d22e8eb183957ae7ade9e4bf7, c3ec44ab4526bbc4b6c9fc845af86488244f4c9b 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 e7339db13b9ddb63417b12da55fd6191e59f7442 or 4f6a8f10182c3a9d22e8eb183957ae7ade9e4bf7 or c3ec44ab4526bbc4b6c9fc845af86488244f4c9b or b9232421a77a649c9376c99fdfc8cb7f79cad34c, whichever matches your release line, or a later version.
- Update Linux Kernel to 6.6.136 or 6.12.83 or 6.18.24 or 6.19.14, whichever matches your release line, or a later version.
Affected products and versions
| Vendor | Product | Affected versions | Fixed in |
|---|---|---|---|
| Linux | Linux | 5f7b0569460b7d8d01ca776430a00505a68b7584 up to, but not including, e7339db13b9ddb63417b12da55fd6191e59f7442; 5f7b0569460b7d8d01ca776430a00505a68b7584 up to, but not including, 4f6a8f10182c3a9d22e8eb183957ae7ade9e4bf7; 5f7b0569460b7d8d01ca776430a00505a68b7584 up to, but not including, c3ec44ab4526bbc4b6c9fc845af86488244f4c9b; 5f7b0569460b7d8d01ca776430a00505a68b7584 up to, but not including, b9232421a77a649c9376c99fdfc8cb7f79cad34c; 5f7b0569460b7d8d01ca776430a00505a68b7584 up to, but not including, 0c739f3785f84af695952c2bac8be2f45082c9b8; 5f7b0569460b7d8d01ca776430a00505a68b7584 up to, but not including, 900a4e0910e98b8caef117d5df00471fa438dcf9; 5f7b0569460b7d8d01ca776430a00505a68b7584 up to, but not including, bdf206e740bf2919d818f132c8c9cc7ed91d11c0; 5f7b0569460b7d8d01ca776430a00505a68b7584 up to, but not including, 39897df386376912d561d4946499379effa1e7ef; and 1 more ranges | e7339db13b9ddb63417b12da55fd6191e59f7442, 4f6a8f10182c3a9d22e8eb183957ae7ade9e4bf7, c3ec44ab4526bbc4b6c9fc845af86488244f4c9b, b9232421a77a649c9376c99fdfc8cb7f79cad34c, 0c739f3785f84af695952c2bac8be2f45082c9b8, 900a4e0910e98b8caef117d5df00471fa438dcf9 |
| Siemens | SIMATIC S7-1500 TM MFP - GNU/Linux subsystem | all versions | Not stated |
| Linux | Linux Kernel | 3.3 up to, but not including, 6.6.136; 6.7 up to, but not including, 6.12.83; 6.13 up to, but not including, 6.18.24; 6.19 up to, but not including, 6.19.14; 7.0 | 6.6.136, 6.12.83, 6.18.24, 6.19.14 |
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: af_unix: read UNIX_DIAG_VFS data under unix_state_lock Exact UNIX diag lookups hold a reference to the socket, but not to u->path. Meanwhile, unix_release_sock() clears u->path under unix_state_lock() and drops the path reference after unlocking. Read the inode and device numbers for UNIX_DIAG_VFS while holding unix_state_lock(), then emit the netlink attribute after dropping the lock. This keeps the VFS data stable while the reply is being built.
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/0c739f3785f84af695952c2bac8be2f45082c9b8
- git.kernel.org/stable/c/39897df386376912d561d4946499379effa1e7ef
- git.kernel.org/stable/c/900a4e0910e98b8caef117d5df00471fa438dcf9
- git.kernel.org/stable/c/b9232421a77a649c9376c99fdfc8cb7f79cad34c
- git.kernel.org/stable/c/bdf206e740bf2919d818f132c8c9cc7ed91d11c0
Other references
Recent Concurrent Execution using Shared Resource with Improper Synchronization vulnerabilities
- 7.5 High severity
- 7.8 High severity
- 7.5 High severity
- 8.3 High severity
- 7.8 High severity
- 7.8 High severity
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