CVE-2025-21648: Linux kernel · netfilter: conntrack: clamp maximum hashtable size to INT_MAX
Affects Linux kernelSource GCVE Database
Not known to be exploited.
Data as of 10 Nov 2026, 14:48 UTC
Rated Low by Threat Radar's AI analysis · No CVSS score from NVD or the CNA
Thin evidence
One scorer or noneExploitation evidence
Disclosed: evidence found.
CVE published 19 Jan 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 has been applied in the Linux kernel to clamp the maximum conntrack hashtable size to INT_MAX, preventing the warning condition. Users should update to a kernel version that includes this fix. No additional mitigation is indicated.
Description
A vulnerability in the Linux kernel's netfilter conntrack subsystem was fixed by clamping the maximum hashtable size to INT_MAX. Without this clamp, resizing the hashtable could trigger a WARN_ON_ONCE warning in the kernel memory allocator due to unset __GFP_NOWARN flags. This issue occurs only during hashtable resizing from the initial network namespace.
References
- git.kernel.org/stable/c/a965f7f0ea3ae61b9165bed619d5d6da02c75f80 (opens in a new tab)
- git.kernel.org/stable/c/b1b2353d768f1b80cd7fe045a70adee576b9b338 (opens in a new tab)
- git.kernel.org/stable/c/5552b4fd44be3393b930434a7845d8d95a2a3c33 (opens in a new tab)
- git.kernel.org/stable/c/d5807dd1328bbc86e059c5de80d1bbee9d58ca3d (opens in a new tab)
- git.kernel.org/stable/c/f559357d035877b9d0dcd273e0ff83e18e1d46aa (opens in a new tab)
- git.kernel.org/stable/c/b541ba7d1f5a5b7b3e2e22dc9e40e18a7d6dbc13 (opens in a new tab)
- lists.debian.org/debian-lts-announce/2025/03/msg00001.html (opens in a new tab)
- lists.debian.org/debian-lts-announce/2025/03/msg00002.html (opens in a new tab)
- cert-portal.siemens.com/productcert/html/ssa-265688.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)