CVE-2026-99064 cipso: adjust cached option offsets when removing CIPSO
- Exploited in the wild
- Not known
- Fix
- Available
What is CVE-2026-99064?
CVE-2026-99064 is a high-severity vulnerability in Linux, published on 23 Oct 2026.
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.
Which versions are affected by CVE-2026-99064?
How do I fix CVE-2026-99064?
Upgrade to a fixed version.
Is CVE-2026-99064 being exploited?
There is no known exploitation of CVE-2026-99064 in the wild and no public exploit code.
Sources
Also known as BELL-CVE-2026-99064, DEBIAN-CVE-2026-99064, GHSA-23p2-8f9v-3g5m, UBUNTU-CVE-2026-99064.