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VulnerabilityPublished Updated

CVE-2025-21629: Linux kernel · net: reenable NETIF_F_IPV6_CSUM offload for BIG TCP packets

Source GCVE Database

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Not known to be exploited · CVSS 5.5 Medium.

Data as of 30 Oct 2026, 01:00 UTC

CVSS 3.1 base score
5.5Medium
How severe the flaw is on the 0–10 CVSS scale.
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 15 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 29 Oct 2026.

What to do

AI-suggested

A fix has been implemented in the Linux kernel to re-enable hardware checksum offload for BIG TCP packets on devices that support BIG TCP TSO. Users should update to the kernel version containing this fix once available. Since this is a kernel-level fix, applying the official kernel update is the recommended mitigation.

Description

CVE-2025-21629 addresses a vulnerability in the Linux kernel related to the handling of hardware checksum offload for IPv6 packets with extension headers, specifically for BIG TCP packets. A previous commit disabled hardware offload for IPv6 packets with extension headers on devices advertising NETIF_F_IPV6_CSUM, causing warnings and potential issues with packet transmission. This update re-enables the offload feature for BIG TCP packets on devices that support BIG TCP TSO, restoring previous behavior for extension headers that are not transmitted by physical devices.

References

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