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Advisory severityHigh7.0Red Hat Linux

High [CVE-2026-63993] do not reuse cached ip_hdr value after skb_tunnel_check_pmtu

This high-severity Red Hat Linux advisory covers CVE-2026-63993 affecting Red Hat Enterprise Linux 10.0 Extended Update Support, Red Hat Enterprise Linux 9.4 Update Services for SAP Solutions, Red Hat Enterprise Linux 9.6 Extended Update Support.

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

CVE-2026-63993 Source published Source updated

VulniPulse record published Record updated

CVE-2026-63993
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: vxlan: do not reuse cached ip_hdr() value after skb_tunnel_check_pmtu() skb_tunnel_check_pmtu() can change skb->head. Reusing old_iph afer skb_tunnel_check_pmtu() can cause an UAF.

Use instead ip_hdr(skb) as done in drivers/net/bareudp.c and drivers/net/geneve.c. Found by Sashiko.

A flaw was found in the Linux kernel's Virtual Extensible LAN (VXLAN) module. This vulnerability occurs because a cached IP header pointer is improperly reused after a Path Maximum Transmission Unit (PMTU) check.

When the packet's head is modified during the PMTU check, the old cached IP header pointer becomes invalid, leading to a Use-After-Free (UAF) condition. This memory corruption flaw can potentially allow an attacker to cause a system crash or execute arbitrary code.

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 10.0 Extended Update Support; Red Hat Enterprise Linux 9; Red Hat Enterprise Linux 9.4 Update Services for SAP Solutions; Red Hat Enterprise Linux 9.6 Extended Update Support.

Red Hat lists Red Hat Enterprise Linux 6; Red Hat Enterprise Linux 7; Red Hat Enterprise Linux 8 as not affected.

Affected products named by the advisory: Red Hat package: kernel-rt.

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 7 days ago·verify at source

Fixed versions
  • kernel-0:6.12.0-211.52.1.el10_2
  • kernel-0:6.12.0-55.111.1.el10_0
  • kernel-0:5.14.0-687.55.1.el9_8
  • kernel-0:5.14.0-427.158.1.el9_4
  • kernel-0:5.14.0-570.152.1.el9_6
  • RHSA-2026:64775
  • RHSA-2026:83707
  • RHSA-2026:76739
  • RHSA-2026:91489
  • RHSA-2026:91492

Official advisory · high-confidence parse· fetched 7 days ago·verify at source

Mitigation

Upgrade to a fixed release: kernel-0:6.12.0-211.52.1.el10_2, kernel-0:6.12.0-55.111.1.el10_0, kernel-0:5.14.0-687.55.1.el9_8, kernel-0:5.14.0-427.158.1.el9_4, kernel-0:5.14.0-570.152.1.el9_6, RHSA-2026:64775. That is the remediation for this advisory.

The vendor advisory may list interim mitigations or workarounds not captured here. Review it before change work.

Official advisory · high-confidence parse· fetched 7 days ago·verify at source

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