CVE-2025-21864: Linux kernel · NULL Pointer Dereference
Affects Linux kernelSource GCVE Database
Not known to be exploited · CVSS 7.8 High.
Data as of 10 Nov 2026, 13:49 UTC
Contested
Scorers differ by 2 or more points| CNA (Linux) | CVSS 3.1 | 7.8 |
|---|---|---|
| CISA-ADP | CVSS 3.1 | 5.5 |
CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:HExploitation evidence
Disclosed: evidence found.
CVE published 12 Mar 2025
Detectable: no evidence on record.
No public nuclei template indexed
Weaponized: no evidence on record.
No public exploit code indexed in Metasploit or Exploit-DB
Exploited in the wildExploited: no evidence on record.
Not in CISA KEV and no source reports exploitation
Observed by OffSeq MirageSeen by 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 for this vulnerability has been implemented in the Linux kernel by ensuring the secpath reference is dropped simultaneously with the destination reference in the TCP receive path. Users and administrators should apply the official Linux kernel updates that include this fix. Since this is a kernel-level issue, upgrading to a patched kernel version is the recommended mitigation. No additional mitigations or workarounds are indicated by the vendor advisory.
Description
CVE-2025-21864 is a high-severity vulnerability in the Linux kernel related to TCP processing and security path (secpath) reference management. The flaw involves lingering references to xfrm_state objects due to deferred freeing of socket buffers (skb) when network namespaces (netns) are deleted. This can cause unexpected references to security states, potentially leading to memory management issues. The issue arises because the secpath attached to an skb is not dropped at the same time as the destination (dst) is dropped, allowing references to persist longer than intended. The vulnerability was reported by Xiumei and involves complex interactions with TCP, IPComp6, and network namespaces. The fix involves dropping the secpath alongside the dst in the TCP receive path once it is no longer needed, while carefully handling extensions like MPTCP.
References
- git.kernel.org/stable/c/87858bbf21da239ace300d61dd209907995c0491 (opens in a new tab)
- git.kernel.org/stable/c/f1d5e6a5e468308af7759cf5276779d3155c5e98 (opens in a new tab)
- git.kernel.org/stable/c/cd34a07f744451e2ecf9005bb7d24d0b2fb83656 (opens in a new tab)
- git.kernel.org/stable/c/69cafd9413084cd5012cf5d7c7ec6f3d493726d9 (opens in a new tab)
- git.kernel.org/stable/c/9b6412e6979f6f9e0632075f8f008937b5cd4efd (opens in a new tab)
- lists.debian.org/debian-lts-announce/2025/05/msg00045.html (opens in a new tab)
- cert-portal.siemens.com/productcert/html/ssa-082556.html (opens in a new tab)
- cert-portal.siemens.com/productcert/html/ssa-019113.html (opens in a new tab)
- cert-portal.siemens.com/productcert/html/ssa-457936.html (opens in a new tab)
- cert-portal.siemens.com/productcert/html/ssa-784472.html (opens in a new tab)