What is CVE-2026-63992?

CVE-2026-63992 is a critical-severity vulnerability in Linux. CVSS score: 9.1/10. Published 2026-07-19.

How severe is CVE-2026-63992?

Critical severity. CVSS v3 base score is 9.1 out of 10.

Vulnerability in Linux

CVE-2026-63992

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.

EPSS: 0.005 (41.8th percentile) — read the EPSS interpretation.

CVSS v3 metric

CVSS v3 base score 9.1 (Critical). Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:H.

Affected products

Linux — versions 4cb47a8644cc9eb8ec81190a50e79e6530d0297f, 5.9, 0

References

Frequently asked questions

What is CVE-2026-63992?: CVE-2026-63992 is a critical-severity vulnerability in Linux. CVSS score: 9.1/10. Published 2026-07-19.
How severe is CVE-2026-63992?: Critical severity. CVSS v3 base score is 9.1 out of 10.