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VulnerabilityPublished Updated

CVE-2025-21635: Linux kernel · rds: sysctl: rds_tcp_{rcv,snd}buf: avoid using current->nsproxy

Affects Linux kernelSource GCVE Database

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Not known to be exploited · CVSS 5.5 Medium.

Data as of 30 Oct 2026, 14:18 UTC

CVSS 3.1 base score
5.5Medium
How severe the flaw is on the 0–10 CVSS scale.

Thin evidence

One scorer or none
CVSS scores by source
CISA-ADPCVSS 3.15.5
CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H

Exploitation evidence

  1. Disclosed: evidence found.

    CVE published 19 Jan 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 30 Oct 2026.

What to do

AI-suggested

A fix has been implemented in the Linux kernel to avoid using current->nsproxy in the rds_tcp_{rcv,snd}buf sysctl code. Users should update to the fixed Linux kernel version once available. Since this is a kernel-level issue, applying the official kernel update is the recommended mitigation.

Description

CVE-2025-21635 is a medium severity vulnerability in the Linux kernel related to the rds_tcp_{rcv,snd}buf sysctl interface. It involves improper use of the current->nsproxy pointer, which can be NULL in some cases, leading to a null pointer dereference and kernel crash (Oops). The issue arises because using the 'net' structure via 'current' is inconsistent and unsafe, especially when the current task is exiting. The vulnerability has been resolved by avoiding the use of current->nsproxy and instead obtaining the per-netns structure from the table data.

References

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