CRITICAL: CVE-2026-63992 (CVSS 9.1) — multiple products

CVE: CVE-2026-63992

CVSS: 9.1 (3.1) — CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:H

Severity: CRITICAL

Status: Critical advisory

Affected

_See vendor advisory_

Summary

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

tunnels: do not assume transport header in iptunnel_pmtud_check_icmp()

In some cases, iptunnel_pmtud_check_icmp() can be called while

skb transport header is not set.

This triggers an out-of-bound access, because

(typeof(skb->transport_header))~0U is 65535.

Access the icmp header based on IPv4 network header,

after making sure icmp->type is present in skb linear part.

Note that iptunnel_pmtud_check_icmpv6()) is fine.

Verified Sources

• NVD entry
• GitHub Advisory
• MITRE

References

• https://git.kernel.org/stable/c/43368636c663cff6e59dde93cf4b8e43ac28eb93
• https://git.kernel.org/stable/c/509323077ef79a26ba0c60bb556e45c12c398b2d
• https://git.kernel.org/stable/c/5a92cb45e34749865d03daf8d3500f77b5f6644c
• https://git.kernel.org/stable/c/7f4f7efe7f30edd29c4988de01728bf2398217e4
• https://git.kernel.org/stable/c/a096b6e34f602950af9a2b0856cd93a5f4c276d7
• https://git.kernel.org/stable/c/c7b7ec3e69e673c0d6b57f74d21da50c485c598e
• https://git.kernel.org/stable/c/cb549df9ce4ee15c9d5b19ddab12cf2128e4313c
• https://git.kernel.org/stable/c/e917d0c69f01af2bb4fbea2b66d560a53b3ac7ec

_Validated by the Lyrie Threat Intelligence Pipeline — 3 independent sources confirmed before publication. No speculation._