---
id: CVE-2026-72400
title: 'seg6: validate SRH length before reading fixed fields'
summary: |-
  In the Linux kernel, the following vulnerability has been resolved:

  seg6: validate SRH length before reading fixed fields

  seg6_validate_srh() reads fixed SRH fields such as srh->type and
  srh->hdrlen before checking that the supplied le…
severity: high
cvss: 7.8
cvssVector: 'CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H'
cvssSource: cna
vendor: Linux
product: Linux
affected:
  - >-
    Linux >= fe94cc290f535709d3c5ebd1e472dfd0aec7ee79 <
    715eb12e453df752f1b4baaf972c3acff0ab9402
  - >-
    Linux >= fe94cc290f535709d3c5ebd1e472dfd0aec7ee79 <
    7247d05c987c3eec4bb7c2306dbd77ecdf3b7c73
  - >-
    Linux >= fe94cc290f535709d3c5ebd1e472dfd0aec7ee79 <
    071f1a38d7ddbadee29c09b9e3ee0ff3a61e6a0e
  - >-
    Linux >= fe94cc290f535709d3c5ebd1e472dfd0aec7ee79 <
    804bb969f194c93497ba632b98343794c6367fdc
  - >-
    Linux >= fe94cc290f535709d3c5ebd1e472dfd0aec7ee79 <
    0fc7069d39239978130c37ebceaec85c8948d3f1
  - >-
    Linux >= fe94cc290f535709d3c5ebd1e472dfd0aec7ee79 <
    8dba7a94a269b88e500aafc25ad567ef6a423698
  - >-
    Linux >= fe94cc290f535709d3c5ebd1e472dfd0aec7ee79 <
    c9961336aa5ff83092f23e33ee86666a9dbd1b2a
  - >-
    Linux >= fe94cc290f535709d3c5ebd1e472dfd0aec7ee79 <
    a75d99f46bf21b45965ce39c5cfb3b8bb5ffb1aa
  - Linux 4.18
ssvc:
  exploitation: none
  automatable: 'no'
  technicalImpact: total
  timestamp: '2026-10-16T18:48:57.930959Z'
published: '2026-08-15'
updated: '2026-10-16'
sourceUpdated: '2026-10-16T18:55:21.670Z'
source: CVEORG
sourceUrl: 'https://www.cve.org/CVERecord?id=CVE-2026-72400'
references:
  - url: 'https://git.kernel.org/stable/c/715eb12e453df752f1b4baaf972c3acff0ab9402'
  - url: 'https://git.kernel.org/stable/c/7247d05c987c3eec4bb7c2306dbd77ecdf3b7c73'
  - url: 'https://git.kernel.org/stable/c/071f1a38d7ddbadee29c09b9e3ee0ff3a61e6a0e'
  - url: 'https://git.kernel.org/stable/c/804bb969f194c93497ba632b98343794c6367fdc'
  - url: 'https://git.kernel.org/stable/c/0fc7069d39239978130c37ebceaec85c8948d3f1'
  - url: 'https://git.kernel.org/stable/c/8dba7a94a269b88e500aafc25ad567ef6a423698'
  - url: 'https://git.kernel.org/stable/c/c9961336aa5ff83092f23e33ee86666a9dbd1b2a'
  - url: 'https://git.kernel.org/stable/c/a75d99f46bf21b45965ce39c5cfb3b8bb5ffb1aa'
tags:
  - cve.org
epss: 0.00176
epssPercentile: 0.06637
ingestedAt: '2026-10-16T19:46:24.400Z'
---

## Overview

In the Linux kernel, the following vulnerability has been resolved:

seg6: validate SRH length before reading fixed fields

seg6_validate_srh() reads fixed SRH fields such as srh->type and
srh->hdrlen before checking that the supplied length covers the fixed
struct ipv6_sr_hdr fields.

The BPF SEG6 encap path reaches this with a BPF program-supplied pointer
and length: bpf_lwt_push_encap() and the SEG6 local BPF END_B6 and
END_B6_ENCAP actions call bpf_push_seg6_encap(), which forwards the
length to seg6_validate_srh() with no minimum-size guard.  A 2-byte SEG6
encap header can therefore make the validator read srh->type at offset 2
beyond the caller-supplied buffer.

Reject lengths shorter than the fixed SRH at the top of
seg6_validate_srh(), before any field is read.  This fixes the BPF helper
path and keeps the common validator robust.

## Affected

- `Linux >= fe94cc290f535709d3c5ebd1e472dfd0aec7ee79 < 715eb12e453df752f1b4baaf972c3acff0ab9402`
- `Linux >= fe94cc290f535709d3c5ebd1e472dfd0aec7ee79 < 7247d05c987c3eec4bb7c2306dbd77ecdf3b7c73`
- `Linux >= fe94cc290f535709d3c5ebd1e472dfd0aec7ee79 < 071f1a38d7ddbadee29c09b9e3ee0ff3a61e6a0e`
- `Linux >= fe94cc290f535709d3c5ebd1e472dfd0aec7ee79 < 804bb969f194c93497ba632b98343794c6367fdc`
- `Linux >= fe94cc290f535709d3c5ebd1e472dfd0aec7ee79 < 0fc7069d39239978130c37ebceaec85c8948d3f1`
- `Linux >= fe94cc290f535709d3c5ebd1e472dfd0aec7ee79 < 8dba7a94a269b88e500aafc25ad567ef6a423698`
- `Linux >= fe94cc290f535709d3c5ebd1e472dfd0aec7ee79 < c9961336aa5ff83092f23e33ee86666a9dbd1b2a`
- `Linux >= fe94cc290f535709d3c5ebd1e472dfd0aec7ee79 < a75d99f46bf21b45965ce39c5cfb3b8bb5ffb1aa`
- `Linux 4.18`

## Remediation

Refer to the linked advisories for vendor-supplied fixes and affected version ranges.