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VulnerabilityPublished Updated

CVE-2025-21648: Linux kernel · netfilter: conntrack: clamp maximum hashtable size to INT_MAX

Affects Linux kernelSource GCVE Database

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Not known to be exploited.

Data as of 10 Nov 2026, 14:48 UTC

Severity
Low

Rated Low by Threat Radar's AI analysis · No CVSS score from NVD or the CNA

Thin evidence

One scorer or none

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 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

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