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CVE-2026-63992

CRITICALCVSS 9.1/10EPSS 0.51%

Last modified

CVE-2026-63992 is a critical-severity vulnerability rated 9.1/10 on the CVSS scale. 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 estimates a 0.51% chance of exploitation in the next 30 days.

Description

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.

Metrics

CVSS 3.1
9.1/10

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

EPSS Probability
0.51%

40.9th percentile

Probability of exploitation in the next 30 days. Learn more

Affected Software

Source: CNA advisory (CVE.org). NVD analysis pending.

VendorProductVersions
LinuxLinux>= 4cb47a8644cc9eb8ec81190a50e79e6530d0297f, < 5a92cb45e34749865d03daf8d3500f77b5f6644c; >= 4cb47a8644cc9eb8ec81190a50e79e6530d0297f, < c7b7ec3e69e673c0d6b57f74d21da50c485c598e; >= 4cb47a8644cc9eb8ec81190a50e79e6530d0297f, < 7f4f7efe7f30edd29c4988de01728bf2398217e4; >= 4cb47a8644cc9eb8ec81190a50e79e6530d0297f, < e917d0c69f01af2bb4fbea2b66d560a53b3ac7ec; >= 4cb47a8644cc9eb8ec81190a50e79e6530d0297f, < a096b6e34f602950af9a2b0856cd93a5f4c276d7; >= 4cb47a8644cc9eb8ec81190a50e79e6530d0297f, < 43368636c663cff6e59dde93cf4b8e43ac28eb93; >= 4cb47a8644cc9eb8ec81190a50e79e6530d0297f, < cb549df9ce4ee15c9d5b19ddab12cf2128e4313c; >= 4cb47a8644cc9eb8ec81190a50e79e6530d0297f, < 509323077ef79a26ba0c60bb556e45c12c398b2d
LinuxLinux5.9

References

Timeline

Published
Last Modified
Status
Awaiting Analysis

Frequently Asked Questions

What is 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.
How severe is CVE-2026-63992?
CVE-2026-63992 has a CVSS score of 9.1/10 (CRITICAL severity). The EPSS model estimates a 0.51% probability of exploitation in the next 30 days.
How do I fix CVE-2026-63992?
Check the vendor references and advisories linked above for patched versions and mitigation guidance. You can also run a Strix scan to test if your systems are affected.

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Source: NVD / NIST