CVE-2025-21629: Linux kernel · net: reenable NETIF_F_IPV6_CSUM offload for BIG TCP packets
Source GCVE Database
Not known to be exploited · CVSS 5.5 Medium.
Data as of 30 Oct 2026, 01:00 UTC
CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:HExploitation evidence
Disclosed: evidence found.
CVE published 15 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 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
- nvd.nist.gov/vuln/detail/CVE-2025-21629 (opens in a new tab)
- git.kernel.org/stable/c/68e068cabd2c6c533ef934c2e5151609cf6ecc6d (opens in a new tab)
- git.kernel.org/stable/c/95ccf006bbc8b59044313b8c309dcf29c546abd4 (opens in a new tab)
- git.kernel.org/stable/c/ac9cfef69565021c9e1022a493a9c40b03e2caf9 (opens in a new tab)
- git.kernel.org/stable/c/d3b7a9c7597b779039a51d7b34116fbe424bf2b7 (opens in a new tab)
- lists.debian.org/debian-lts-announce/2025/03/msg00001.html (opens in a new tab)