Linux: Use After Free
CVE-2025-39864 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 a8bb681e879ca3c9f722aa08d3d7ae41c42a8807, a97a9791e455bb0cd5e7a38b5abcb05523d4e21c, ff040562c10a540b8d851f7f4145fa112977f853 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 0.24% 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 a8bb681e879ca3c9f722aa08d3d7ae41c42a8807 or a97a9791e455bb0cd5e7a38b5abcb05523d4e21c or ff040562c10a540b8d851f7f4145fa112977f853 or 6854476d9e1aeaaf05ebc98d610061c2075db07d, whichever matches your release line, or a later version.
- Update RUGGEDCOM RST2428P to V3.3 or a later version.
- Update SCALANCE XC-300/XR-300/XC-400/XR-500WG/XR-500 family to V3.3 or a later version.
Affected products and versions
| Vendor | Product | Affected versions | Fixed in |
|---|---|---|---|
| Linux | Linux | 3ab8227d3e7d1d2bf1829675d3197e3cb600e9f6 up to, but not including, a8bb681e879ca3c9f722aa08d3d7ae41c42a8807; 3ab8227d3e7d1d2bf1829675d3197e3cb600e9f6 up to, but not including, a97a9791e455bb0cd5e7a38b5abcb05523d4e21c; 3ab8227d3e7d1d2bf1829675d3197e3cb600e9f6 up to, but not including, ff040562c10a540b8d851f7f4145fa112977f853; 3ab8227d3e7d1d2bf1829675d3197e3cb600e9f6 up to, but not including, 6854476d9e1aeaaf05ebc98d610061c2075db07d; 3ab8227d3e7d1d2bf1829675d3197e3cb600e9f6 up to, but not including, b7d08929178c16398278613df07ad65cf63cce9d; 3ab8227d3e7d1d2bf1829675d3197e3cb600e9f6 up to, but not including, 5b7ae04969f822283a95c866967e42b4d75e0eef; 3ab8227d3e7d1d2bf1829675d3197e3cb600e9f6 up to, but not including, 912c4b66bef713a20775cfbf3b5e9bd71525c716; 3ab8227d3e7d1d2bf1829675d3197e3cb600e9f6 up to, but not including, 26e84445f02ce6b2fe5f3e0e28ff7add77f35e08; and 1 more ranges | a8bb681e879ca3c9f722aa08d3d7ae41c42a8807, a97a9791e455bb0cd5e7a38b5abcb05523d4e21c, ff040562c10a540b8d851f7f4145fa112977f853, 6854476d9e1aeaaf05ebc98d610061c2075db07d, b7d08929178c16398278613df07ad65cf63cce9d, 5b7ae04969f822283a95c866967e42b4d75e0eef |
| Siemens | RUGGEDCOM RST2428P | before V3.3 | V3.3 |
| Siemens | SCALANCE XC-300/XR-300/XC-400/XR-500WG/XR-500 family | before V3.3 | V3.3 |
| Siemens | SCALANCE XCH328 | before V3.3 | V3.3 |
| Siemens | SCALANCE XCM324 | before V3.3 | V3.3 |
| Siemens | SCALANCE XCM328 | before V3.3 | V3.3 |
| Siemens | SCALANCE XCM332 | before V3.3 | V3.3 |
| Siemens | SCALANCE XRH334 (24 V DC, 8xFO, CC) | before V3.3 | V3.3 |
| Siemens | SCALANCE XRM334 (230 V AC, 12xFO) | before V3.3 | V3.3 |
| Siemens | SCALANCE XRM334 (230 V AC, 8xFO) | before V3.3 | V3.3 |
| Siemens | SCALANCE XRM334 (230V AC, 2x10G, 24xSFP, 8xSFP+) | before V3.3 | V3.3 |
| Siemens | SCALANCE XRM334 (24 V DC, 12xFO) | before V3.3 | V3.3 |
| Siemens | SCALANCE XRM334 (24 V DC, 8xFO) | before V3.3 | V3.3 |
| Siemens | SCALANCE XRM334 (24V DC, 2x10G, 24xSFP, 8xSFP+) | before V3.3 | V3.3 |
| Siemens | SCALANCE XRM334 (2x230 V AC, 12xFO) | before V3.3 | V3.3 |
| Siemens | SCALANCE XRM334 (2x230 V AC, 8xFO) | before V3.3 | V3.3 |
| Siemens | SCALANCE XRM334 (2x230V AC, 2x10G, 24xSFP, 8xSFP+) | before V3.3 | V3.3 |
| Siemens | SIMATIC CN 4100 | before V5.0 | V5.0 |
| Linux | Linux Kernel | 5.4 up to, but not including, 5.4.299; 5.5 up to, but not including, 5.10.243; 5.11 up to, but not including, 5.15.192; 5.16 up to, but not including, 6.1.151; 6.2 up to, but not including, 6.6.105; 6.7 up to, but not including, 6.12.46; 6.13 up to, but not including, 6.16.6; 6.17 | 5.4.299, 5.10.243, 5.15.192, 6.1.151, 6.6.105, 6.12.46 |
| Debian | Debian Linux | 11.0 | Not stated |
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 | 8.8 | High | CNA |
| CVSS 3.1 | 7.8 | High | NVD |
Official description
In the Linux kernel, the following vulnerability has been resolved: wifi: cfg80211: fix use-after-free in cmp_bss() Following bss_free() quirk introduced in commit 776b3580178f ("cfg80211: track hidden SSID networks properly"), adjust cfg80211_update_known_bss() to free the last beacon frame elements only if they're not shared via the corresponding 'hidden_beacon_bss' pointer.
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/26e84445f02ce6b2fe5f3e0e28ff7add77f35e08
- git.kernel.org/stable/c/5b7ae04969f822283a95c866967e42b4d75e0eef
- git.kernel.org/stable/c/6854476d9e1aeaaf05ebc98d610061c2075db07d
- git.kernel.org/stable/c/912c4b66bef713a20775cfbf3b5e9bd71525c716
- git.kernel.org/stable/c/a8bb681e879ca3c9f722aa08d3d7ae41c42a8807
- git.kernel.org/stable/c/a97a9791e455bb0cd5e7a38b5abcb05523d4e21c
- git.kernel.org/stable/c/b7d08929178c16398278613df07ad65cf63cce9d
- git.kernel.org/stable/c/ff040562c10a540b8d851f7f4145fa112977f853
Third-party and government advisories
- lists.debian.org/debian-lts-announce/2025/10/msg00007.htmlMailing List, Third Party Advisory
- lists.debian.org/debian-lts-announce/2025/10/msg00008.htmlMailing List, Third Party Advisory
Other references
Recent Use After Free vulnerabilities
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- 7.8 High severity
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