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Advisory severityHigh7.0Red Hat Linux

High [CVE-2026-63994] load network headers after skb_cow in iptunnel_pmtud_build_icmp[v6]

This high-severity Red Hat Linux advisory covers CVE-2026-63994 affecting Red Hat Enterprise Linux 10, Red Hat Enterprise Linux 8, Red Hat Enterprise Linux 9.

Aggregated and source-linked by VulniPulse. Data sources, validation and limitations.

CVE-2026-63994 Source published Source updated

VulniPulse record published Record updated

CVE-2026-63994
Affected products & platforms
Red Hat LinuxLinux Kernel
Open source advisory

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Summary

In the Linux kernel, the following vulnerability has been resolved: tunnels: load network headers after skb_cow() in iptunnel_pmtud_build_icmp[v6]() Sashiko found that iptunnel_pmtud_build_icmp() and iptunnel_pmtud_build_icmpv6() were caching ip_hdr() and ipv6_hdr() before an skb_cow() call which can reallocate skb->head.

Fix this possible UAF by initializing the local variables after the skb_cow() call. Remove skb_reset_network_header() calls which were not needed.

This vulnerability, categorized as a Use-After-Free (UAF), arises from improper handling of network header pointers during certain packet processing operations.

Specifically, functions responsible for building Internet Control Message Protocol (ICMP) packets for Path MTU Discovery (PMTUD) cache header information before memory reallocations, which can lead to the use of freed memory. A local attacker could potentially leverage this to cause a system crash, resulting in a denial of service.

Red Hat severity: Important — CVSS 7 (CVSS:3.1/AV:L/AC:H/PR:L/UI:N/S:U/C:H/I:H/A:H). Weakness: CWE-825.

Affected Red Hat products: Red Hat Enterprise Linux 10; Red Hat Enterprise Linux 8; Red Hat Enterprise Linux 9; Shadow Migration Toolkit for Virtualization for RHEL 10. Red Hat lists Red Hat Enterprise Linux 7 as not affected.

Red Hat fixing advisory: RHSA-2026:76738, RHSA-2026:75746, RHSA-2026:75747, RHSA-2026:76739.

Affected versions

No affected-version range was extracted from the source record. The vendor advisory is authoritative. Check it before change work.

Official advisory · high-confidence parse· fetched 6 days ago·verify at source

Fixed versions
  • kernel-0:6.12.0-211.63.1.el10_2
  • kernel-rt-0:4.18.0-553.171.1.rt7.512.el8_10
  • kernel-0:4.18.0-553.171.1.el8_10
  • kernel-0:5.14.0-687.55.1.el9_8
  • RHSA-2026:76738
  • RHSA-2026:75746
  • RHSA-2026:75747
  • RHSA-2026:76739

Official advisory · high-confidence parse· fetched 6 days ago·verify at source

Mitigation checklist

Recommended fix / mitigation
  • Mitigation for this issue is either not available or the currently available options do not meet the Red Hat Product Security criteria comprising ease of use and deployment, applicability to widespread installation base, or stability.

Official advisory · high-confidence parse· fetched 6 days ago·verify at source

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