Linux: Use After Free
CVE-2025-21923 is a high-severity use after free 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 026714ec7546de741826324a6a1914c91024d06c, a899adf7063c6745aaff1ec869f3c7f6329ed0a1, ea3f18d2f02629653b7bfe42607737ccd1343e54 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 0.21% 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 026714ec7546de741826324a6a1914c91024d06c or a899adf7063c6745aaff1ec869f3c7f6329ed0a1 or ea3f18d2f02629653b7bfe42607737ccd1343e54 or e53fc232a65f7488ab75d03a5b95f06aaada7262, whichever matches your release line, or a later version.
- Update Linux Kernel to 6.6.83 or 6.12.19 or 6.13.7, whichever matches your release line, or a later version.
Affected products and versions
| Vendor | Product | Affected versions | Fixed in |
|---|---|---|---|
| Linux | Linux | e1147961b2145fa61c3078a4a797d9576cde91ab up to, but not including, 026714ec7546de741826324a6a1914c91024d06c; 3e38cbbfa0a128a9d64773240a9eb3bc7bae3b1a up to, but not including, a899adf7063c6745aaff1ec869f3c7f6329ed0a1; 053fa3888d2a957f4db26c05e503f4c6b9570a30 up to, but not including, ea3f18d2f02629653b7bfe42607737ccd1343e54; 79504249d7e27cad4a3eeb9afc6386e418728ce0 up to, but not including, e53fc232a65f7488ab75d03a5b95f06aaada7262; 6.6.79 up to, but not including, 6.6.83; 6.12.16 up to, but not including, 6.12.19; 6.13.4 up to, but not including, 6.13.7 | 026714ec7546de741826324a6a1914c91024d06c, a899adf7063c6745aaff1ec869f3c7f6329ed0a1, ea3f18d2f02629653b7bfe42607737ccd1343e54, e53fc232a65f7488ab75d03a5b95f06aaada7262, 6.6.83, 6.12.19 |
| Linux | Linux Kernel | 6.6.79 up to, but not including, 6.6.83; 6.12.16 up to, but not including, 6.12.19; 6.13.4 up to, but not including, 6.13.7 | 6.6.83, 6.12.19, 6.13.7 |
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 NVD.
| Scoring system | Score | Severity | Scored by |
|---|---|---|---|
| CVSS 3.1 | 7.8 | High | NVD |
| CVSS 3.1 | 7.8 | High | CISA (ADP) |
Official description
In the Linux kernel, the following vulnerability has been resolved: HID: hid-steam: Fix use-after-free when detaching device When a hid-steam device is removed it must clean up the client_hdev used for intercepting hidraw access. This can lead to scheduling deferred work to reattach the input device. Though the cleanup cancels the deferred work, this was done before the client_hdev itself is cleaned up, so it gets rescheduled. This patch fixes the ordering to make sure the deferred work is properly canceled.
Source: the CVE record as published by its numbering authority, via NVD and CVE.org.
The underlying weakness: Use After Free
The product reuses or references memory after it has been freed. At some point afterward, the memory may be allocated again and saved in another pointer, while the original pointer references a location somewhere within the new allocation. Any operations using the original pointer are no longer valid because the memory belongs to the code that operates on the new pointer.
How developers prevent this class of flaw
- Choose a language that provides automatic memory management.
- When freeing pointers, be sure to set them to NULL once they are freed. However, the utilization of multiple or complex data structures may lower the usefulness of this strategy.
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 Use After Free vulnerabilities
- 7.8 High severity
- 7.8 High severity
- 7.8 High severity
- 7.8 High severity
- 7.8 High severity
- 7.8 High severity
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