CVE-2026-99064cipso: adjust cached option offsets when removing CIPSO

Official description

In the Linux kernel, the following vulnerability has been resolved: cipso: adjust cached option offsets when removing CIPSO cipso_v4_skbuff_delattr() removes the CIPSO bytes but does not adjust cached offsets for options that follow them. For example, with a valid 10-byte CIPSO option followed by a seven-byte RR option, parsing records rr at offset 30. Removing CIPSO moves RR to offset 20, while the cached offset remains 30. Consumers such as ip_forward_options() and __ip_options_echo() then access the wrong bytes; the latter may interpret packet data as the option length and copy it into fixed-size option storage. Mirror cipso_v4_delopt() and subtract cipso_len from the srr, rr, ts and router_alert offsets when they follow CIPSO. cipso_len is the distance the first memmove() shifts those options. The later header move and network-header reset relocate the bytes and their offset base together.

Affected packages & fixed versions

Affected products (as reported)

References

• https://git.kernel.org/stable/c/b965977126a90e01825814c859ba4788691eddd3
• https://git.kernel.org/stable/c/2200fe1d6148b78e1b8f00f4b2bd47760015077f
• https://git.kernel.org/stable/c/6e49d611a9cfbaac927b8fa80ebd4f6b1f37ada0
• https://git.kernel.org/stable/c/6d25ffca055a77787c21a36b66c253f76239411b