CVE-2026-63994 Details
Description
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.
A use-after-free vulnerability has been identified in the Linux kernel's IP tunneling implementation. The issue arises in the 'iptunnel_pmtud_build_icmp' and 'iptunnel_pmtud_build_icmpv6' functions, where network header information is cached before a critical operation that can modify the memory structure of the packet. This flaw could potentially be exploited to access freed memory, leading to undefined behavior.
Users can upgrade to the latest version of the Linux kernel where this vulnerability has been patched. Instructions for upgrading the kernel can be found in the official Linux documentation.
Metrics
CVSS 4.0 Severity and Vector Strings:
No CVSS 4.0 data is available for this CVE.
CVSS 3.x Severity and Vector Strings:
No data available for CVSS Version 2.0 on this CVE.
No SSVC data is available for this CVE.
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Weakness Enumeration
No weakness enumeration is available for this CVE.
Affected Products
No affected product data is available for this CVE.
Change History
2 change records found show changes
| Date | Action | Recorded By |
|---|---|---|
| Jul 20, 2026 | CVE Modified | kernel.org |
| Jul 19, 2026 | New CVE Received | kernel.org |