Instituto Nacional de ciberseguridad. Sección Incibe
Instituto Nacional de Ciberseguridad. Sección INCIBE-CERT

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CVE-2026-63994

Severity CVSS v4.0:
Pending analysis
Type:
Unavailable / Other
Publication date:
19/07/2026
Last modified:
30/07/2026

Description

In the Linux kernel, the following vulnerability has been resolved:<br /> <br /> tunnels: load network headers after skb_cow() in iptunnel_pmtud_build_icmp[v6]()<br /> <br /> Sashiko found that iptunnel_pmtud_build_icmp() and<br /> iptunnel_pmtud_build_icmpv6() were caching ip_hdr() and ipv6_hdr()<br /> before an skb_cow() call which can reallocate skb-&gt;head.<br /> <br /> Fix this possible UAF by initializing the local variables<br /> after the skb_cow() call.<br /> <br /> Remove skb_reset_network_header() calls which were not needed.

Impact

Vector 3.x
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H CVSS v3.1 Severity and Metrics:

Base Score: 9.80 CRITICAL
Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H

Attack Vector (AV): Network
Attack Complexity (AC): Low
Privileges Required (PR): None
User Interaction (UI): None
Scope (S): Unchanged
Confidentiality (C): High
Integrity (I): High
Availability (A): High

Base Score 3.x
9.80
Severity 3.x
CRITICAL

References to Advisories, Solutions, and Tools