CVE-2025-39964
Linux Kernel: Race Condition
As of , CVE-2025-39964 in Linux Kernel is on CISA's list of exploited vulnerabilities: CISA listed it on . Our patch-first group: Patch now.
- Exploited
- Yes: CISA listed it on 18 September 2026
- US federal deadline
- 21 September 20263 days after CISA listed it. US federal civilian agencies must fix it by then.
- Used in ransomware campaigns
- Not known to CISA
- Forensic triage
- Required by CISA under BOD 26-04Agencies must also look for signs that attackers already got in.
- EPSS score
- 0.01Higher than 68% of the CVEs EPSS scores. EPSS estimates the chance of exploitation activity in the next 30 days.
- Public exploit
- None foundNeither Metasploit nor Exploit-DB lists one.
- Fix
- Vendor advice: git.kernel.orgLinks below, from CISA's entry.
What CISA says to do
Apply mitigations in accordance with vendor instructions, ensuring compliance with CISA’s BOD 26-04 Prioritizing Security Updates Based on Risk (see URL in Notes) guidance and CISA’s “Forensics Triage Requirements” (see URL in Notes). Follow applicable BOD 26-04 guidance for cloud services or discontinue use of the product if mitigations are unavailable. Stakeholders are responsible for evaluating each asset's internet exposure and ensuring adherence to BOD 26-04 patching guidelines.
CISA's required action
What the flaw is
Linux Kernel contains a race condition vulnerability which allows concurrent writes to the same AF_ALG socket causing data to be unpredictably interleaved and creating inconsistencies in the socket's internal state.
CISA's description
In the Linux kernel, the following vulnerability has been resolved: crypto: af_alg - Disallow concurrent writes in af_alg_sendmsg Issuing two writes to the same af_alg socket is bogus as the data will be interleaved in an unpredictable fashion. Furthermore, concurrent writes may create inconsistencies in the internal socket state. Disallow this by adding a new ctx->write field that indiciates exclusive ownership for writing.
The CVE record's description, from Linux
- CVE published
- 13 October 2025
- Assigned by
- Linux
- CVSS
- 7.8 High (CVSS 3.1, from the CNA)
- CWE-362
- Concurrent Execution using Shared Resource with Improper Synchronization ('Race Condition')
- CISA SSVC, exploitation
- active
- CISA SSVC, automatable
- no
- CISA SSVC, technical impact
- total
Timeline
- The CVE record was published.
- CISA added it to its list of exploited vulnerabilities.
- The US federal deadline to fix it.
Kernel: other exploited entries
| Vulnerability | Product | Our group | Listed | Deadline | EPSS |
|---|---|---|---|---|---|
| CVE-2025-39682Improper Check for Unusual or Exceptional Conditions | Linux Kernel | Patch nowForensic triage required by CISA | 0.03 | ||
| CVE-2026-53266Out-of-Bounds Write | Linux Kernel | Patch nowForensic triage required by CISA | 0.01 | ||
| CVE-2026-53362Unspecified | Linux Kernel | Patch nowForensic triage required by CISA | 0.01 | ||
| CVE-2021-22555Heap Out-of-Bounds Write | Linux Kernel | Patch this weekMetasploit module; EPSS 0.79; verified Exploit-DB entry | 0.79 | ||
| CVE-2013-6282Improper Input Validation | Linux Kernel | Patch this weekMetasploit module; verified Exploit-DB entry | 0.40 | ||
| CVE-2019-13272Improper Privilege Management | Linux Kernel | Patch this weekMetasploit module; EPSS 0.52; verified Exploit-DB entry | 0.52 | ||
| CVE-2010-3904Improper Input Validation | Linux Kernel | Patch this weekMetasploit module; verified Exploit-DB entry | 0.16 | ||
| CVE-2022-0847Privilege Escalation | Linux Kernel | Patch this weekMetasploit module; EPSS 0.93 | 0.93 | ||
| CVE-2021-3493Privilege Escalation | Linux Kernel | Patch this weekMetasploit module | 0.49 | ||
| CVE-2014-3153Privilege Escalation | Linux Kernel | Patch this weekMetasploit module | 0.37 |
Read further
- CVE recordcve.org
- NVD entrynvd.nist.gov
- CISA's catalogcisa.gov
- EPSS for this CVEapi.first.org