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VulnerabilityPublished Updated

CVE-2025-21718: Linux kernel · net: rose: fix timer races against user threads

Affects Linux kernelSource GCVE Database

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Not known to be exploited · CVSS 7.8 High.

Data as of 10 Nov 2026, 14:04 UTC

CVSS 3.1 base score
7.8High
How severe the flaw is on the 0–10 CVSS scale.

Thin evidence

One scorer or none
CVSS scores by source
CNA (Linux)CVSS 3.17.8
CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H

Exploitation evidence

  1. Disclosed: evidence found.

    CVE published 27 Feb 2025

  2. Detectable: no evidence on record.

    No public nuclei template indexed

  3. Weaponized: no evidence on record.

    No public exploit code indexed in Metasploit or Exploit-DB

  4. Exploited in the wild: no evidence on record.

    Not in CISA KEV and no source reports exploitation

  5. Observed by OffSeq Mirage: no evidence on record.

    No attack traffic recorded by OffSeq Mirage sensors

A missing step is not evidence of safety. Sources: cve.org (opens in a new tab), the Metasploit, Exploit-DB and nuclei-templates index as of 10 Nov 2026.

What to do

AI-suggested

A fix has been implemented in the Linux kernel to add proper checks and rearm timers as needed to prevent races against user threads. Users should apply the official Linux kernel updates that include this fix. Since this is a kernel-level vulnerability, upgrading to a patched kernel version is the recommended remediation. No alternative mitigations are indicated.

Description

CVE-2025-21718 is a high-severity vulnerability in the Linux kernel's net rose module involving timer races against user threads. The issue arises because rose timers only acquire the socket spinlock without verifying if the socket is owned by a user thread, leading to a use-after-free condition. This flaw can cause kernel memory corruption and potentially allow an attacker with local privileges to compromise system integrity and availability.

References

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