Linux: Use After Free
CVE-2025-21762 is a high-severity use after free vulnerability in Linux, with a CVSS 3.1 base score of 8.1 out of 10. It can be exploited remotely over the network by an unauthenticated attacker, without any action from a user. The record lists versions 10f555e3f573d004ae9d89b3276abb58c4ede5c3, 307cd1e2d3cb1cbc6c40c679cada6d7168b18431, d9366ac2f956a1948b68c0500f84a3462ff2ed8a 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 0.66% chance of exploitation within 30 days, higher than 52% of scored CVEs.
High severity with no evidence of exploitation so far.
What to do
- Update Linux to 10f555e3f573d004ae9d89b3276abb58c4ede5c3 or 307cd1e2d3cb1cbc6c40c679cada6d7168b18431 or d9366ac2f956a1948b68c0500f84a3462ff2ed8a or f189654459423d4d48bef2d120b4bfba559e6039, whichever matches your release line, or a later version.
- Update Linux Kernel to 5.4.291 or 5.10.235 or 5.15.179 or 6.1.129, 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.
Affected products and versions
| Vendor | Product | Affected versions | Fixed in |
|---|---|---|---|
| Linux | Linux | 29a26a56803855a79dbd028cd61abee56237d6e5 up to, but not including, 10f555e3f573d004ae9d89b3276abb58c4ede5c3; 29a26a56803855a79dbd028cd61abee56237d6e5 up to, but not including, 307cd1e2d3cb1cbc6c40c679cada6d7168b18431; 29a26a56803855a79dbd028cd61abee56237d6e5 up to, but not including, d9366ac2f956a1948b68c0500f84a3462ff2ed8a; 29a26a56803855a79dbd028cd61abee56237d6e5 up to, but not including, f189654459423d4d48bef2d120b4bfba559e6039; 29a26a56803855a79dbd028cd61abee56237d6e5 up to, but not including, e9f4dee534eb1b225b0a120395ad9bc2afe164d3; 29a26a56803855a79dbd028cd61abee56237d6e5 up to, but not including, 01d1b5c9abcaff29a43f1d17a19c33eec92c7dbe; 29a26a56803855a79dbd028cd61abee56237d6e5 up to, but not including, 2c331718d3389b6c5f6855078ab7171849e016bd; 29a26a56803855a79dbd028cd61abee56237d6e5 up to, but not including, a42b69f692165ec39db42d595f4f65a4c8f42e44; and 1 more ranges | 10f555e3f573d004ae9d89b3276abb58c4ede5c3, 307cd1e2d3cb1cbc6c40c679cada6d7168b18431, d9366ac2f956a1948b68c0500f84a3462ff2ed8a, f189654459423d4d48bef2d120b4bfba559e6039, e9f4dee534eb1b225b0a120395ad9bc2afe164d3, 01d1b5c9abcaff29a43f1d17a19c33eec92c7dbe |
| Siemens | SIMATIC S7-1500 TM MFP - BIOS | all versions | Not stated |
| Siemens | SIMATIC S7-1500 TM MFP - GNU/Linux subsystem | all versions | Not stated |
| Linux | Linux Kernel | 4.4 up to, but not including, 5.4.291; 5.5 up to, but not including, 5.10.235; 5.11 up to, but not including, 5.15.179; 5.16 up to, but not including, 6.1.129; 6.2 up to, but not including, 6.6.79; 6.7 up to, but not including, 6.12.16; 6.13 up to, but not including, 6.13.4; 6.14 | 5.4.291, 5.10.235, 5.15.179, 6.1.129, 6.6.79, 6.12.16 |
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
- HighSuccess depends on conditions outside the attacker's control.
- Privileges required
- NoneNo account or login is needed.
- 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:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:H. Scored by CNA.
| Scoring system | Score | Severity | Scored by |
|---|---|---|---|
| CVSS 3.1 | 8.1 | High | CNA |
| CVSS 3.1 | 7.8 | High | CISA (ADP) |
Official description
In the Linux kernel, the following vulnerability has been resolved: arp: use RCU protection in arp_xmit() arp_xmit() can be called without RTNL or RCU protection. Use RCU protection to avoid potential UAF.
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
- git.kernel.org/stable/c/01d1b5c9abcaff29a43f1d17a19c33eec92c7dbe
- git.kernel.org/stable/c/10f555e3f573d004ae9d89b3276abb58c4ede5c3
- git.kernel.org/stable/c/2c331718d3389b6c5f6855078ab7171849e016bd
- git.kernel.org/stable/c/307cd1e2d3cb1cbc6c40c679cada6d7168b18431
- git.kernel.org/stable/c/a42b69f692165ec39db42d595f4f65a4c8f42e44
- git.kernel.org/stable/c/d9366ac2f956a1948b68c0500f84a3462ff2ed8a
- git.kernel.org/stable/c/e9f4dee534eb1b225b0a120395ad9bc2afe164d3
- git.kernel.org/stable/c/f189654459423d4d48bef2d120b4bfba559e6039
Other references
Recent Use After Free vulnerabilities
- 7.8 High severity
- 7.8 High severity
- 7.8 High severity
- 7.8 High severity
- 9.8 Critical severity
- 7.8 High severity
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