CVE-2025-21629

/// Technical description

In the Linux kernel, the following vulnerability has been resolved:

net: reenable NETIF_F_IPV6_CSUM offload for BIG TCP packets

The blamed commit disabled hardware offoad of IPv6 packets with

extension headers on devices that advertise NETIF_F_IPV6_CSUM,

based on the definition of that feature in skbuff.h:

* * - %NETIF_F_IPV6_CSUM

* - Driver (device) is only able to checksum plain

* TCP or UDP packets over IPv6. These are specifically

* unencapsulated packets of the form IPv6|TCP or

* IPv6|UDP where the Next Header field in the IPv6

* header is either TCP or UDP. IPv6 extension headers

* are not supported with this feature. This feature

* cannot be set in features for a device with

* NETIF_F_HW_CSUM also set. This feature is being

* DEPRECATED (see below).

The change causes skb_warn_bad_offload to fire for BIG TCP

packets.

[ 496.310233] WARNING: CPU: 13 PID: 23472 at net/core/dev.c:3129 skb_warn_bad_offload+0xc4/0xe0

/// Remediation

Check the references section for vendor advisories, patches, and mitigation guidance. If immediate patching is not possible, review the CVSS vector to understand the attack surface and apply compensating controls such as network segmentation or access restrictions.

/// References