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

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CVE-2026-63920

Severity CVSS v4.0:
Pending analysis
Type:
Unavailable / Other
Publication date:
19/07/2026
Last modified:
27/07/2026

Description

In the Linux kernel, the following vulnerability has been resolved:<br /> <br /> ipv6: validate extension header length before copying to cmsg<br /> <br /> ip6_datagram_recv_specific_ctl() builds IPV6_{HOPOPTS,DSTOPTS,RTHDR}<br /> cmsgs (and their IPV6_2292* legacy counterparts) by trusting the<br /> on-wire hdrlen byte (ptr[1]) when computing the put_cmsg() length.<br /> The length was validated only at parse time (ipv6_parse_hopopts(),<br /> etc.). An nftables payload-write expression can rewrite hdrlen after<br /> parsing and before the skb reaches recvmsg; the write itself is<br /> in-bounds but put_cmsg() then reads up to ((hdrlen+1)

Impact

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

Base Score: 7.10 HIGH
Vector: CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:N/A:H

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

Base Score 3.x
7.10
Severity 3.x
HIGH

References to Advisories, Solutions, and Tools