CVE-2026-98573net: skbuff: fix pull-bound underflow in skb_checksum_setup_ipv6()

Official description

In the Linux kernel, the following vulnerability has been resolved: net: skbuff: fix pull-bound underflow in skb_checksum_setup_ipv6() skb_maybe_pull_tail() subtracts skb_headlen(skb) from the unsigned max argument and passes the result to __pskb_pull_tail() as a signed int. The function does not ensure that max is at least skb_headlen(skb). This can happen while parsing IPv6 extension headers when an skb already has a linear area larger than MAX_IPV6_HDR_LEN. Once the parser needs data beyond the linear area, max - skb_headlen(skb) wraps and is converted to a negative delta. __pskb_pull_tail() then passes that negative length to skb_copy_bits(), where it can become a very large copy length. Pass the requested length itself as the pull bound at the three extension-header call sites, so the delta can no longer go negative.

Affected packages & fixed versions

Affected products (as reported)

References

• https://git.kernel.org/stable/c/9c4e432132a97b82edf28fa172c39f743e6bfb26
• https://git.kernel.org/stable/c/718747afa5463d9cc5fd9a09f03b2a492edd9b78
• https://git.kernel.org/stable/c/a0ad0473c09d2e947aecac5c82e637ec85924b12
• https://git.kernel.org/stable/c/b2da5ed3d8c75e1b729a21b6d3beaed415e263f6
• https://git.kernel.org/stable/c/6c28c31f051dbf49c71ba7ab7bb9bc905fa1d14b
• https://git.kernel.org/stable/c/cfa643f2ca36c6f913fe1a2ceb12412ebb0fd962
• https://git.kernel.org/stable/c/d7f474226809471dc7877435e9c492cc914df0bf
• https://git.kernel.org/stable/c/3b4e0b0c008a8c1b474730248cd5b873026c74bd