---
id: CVE-2026-89555
title: 'mpls: reload header after pskb_may_pull()'
summary: |-
  In the Linux kernel, the following vulnerability has been resolved:

  mpls: reload header after pskb_may_pull()

  mpls_select_multipath() calls mpls_multipath_hash() to choose a nexthop
  when an MPLS route has multiple nexthops.  While walk…
severity: critical
cvss: 9.8
cvssVector: 'CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H'
cvssSource: cna
vendor: Linux
product: Linux
affected:
  - >-
    Linux >= 9f427a0e474a67b454420c131709600d44850486 <
    aa4fe0b450a461aa1162fe8375f5d28f4c957df8
  - >-
    Linux >= 9f427a0e474a67b454420c131709600d44850486 <
    b1c0783b2facc398437ad8f8b86c636d7a78f8db
  - >-
    Linux >= 9f427a0e474a67b454420c131709600d44850486 <
    bfaaff99238326166694354a63a76c02563f98b1
  - >-
    Linux >= 9f427a0e474a67b454420c131709600d44850486 <
    d9640239827d6d0cb84263b590f7a4f1596c17eb
  - >-
    Linux >= 9f427a0e474a67b454420c131709600d44850486 <
    fed638a248116b8a249bd4202d28e5934bdc65ad
  - >-
    Linux >= 9f427a0e474a67b454420c131709600d44850486 <
    d82b90a38c2ca8a0694428eab0e9551c23f2447d
  - >-
    Linux >= 9f427a0e474a67b454420c131709600d44850486 <
    49d38c1b4390412f8950d33dfaee0ccbd17beb81
  - >-
    Linux >= 9f427a0e474a67b454420c131709600d44850486 <
    29e63b8d9fc150cc191b1c6eb7e16e1247e1b650
  - Linux ad864d9fce0ec56cc8f6afe5c6a0e6d7f484b9eb
  - Linux >= 4.9.8 < 4.10
  - Linux 4.10
published: '2026-09-11'
updated: '2026-09-14'
sourceUpdated: '2026-09-14T12:00:57.921Z'
source: CVEORG
sourceUrl: 'https://www.cve.org/CVERecord?id=CVE-2026-89555'
references:
  - url: 'https://git.kernel.org/stable/c/aa4fe0b450a461aa1162fe8375f5d28f4c957df8'
  - url: 'https://git.kernel.org/stable/c/b1c0783b2facc398437ad8f8b86c636d7a78f8db'
  - url: 'https://git.kernel.org/stable/c/bfaaff99238326166694354a63a76c02563f98b1'
  - url: 'https://git.kernel.org/stable/c/d9640239827d6d0cb84263b590f7a4f1596c17eb'
  - url: 'https://git.kernel.org/stable/c/fed638a248116b8a249bd4202d28e5934bdc65ad'
  - url: 'https://git.kernel.org/stable/c/d82b90a38c2ca8a0694428eab0e9551c23f2447d'
  - url: 'https://git.kernel.org/stable/c/49d38c1b4390412f8950d33dfaee0ccbd17beb81'
  - url: 'https://git.kernel.org/stable/c/29e63b8d9fc150cc191b1c6eb7e16e1247e1b650'
tags:
  - cve.org
epss: 0.00684
epssPercentile: 0.51172
ingestedAt: '2026-09-14T15:23:07.451Z'
---

## Overview

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

mpls: reload header after pskb_may_pull()

mpls_select_multipath() calls mpls_multipath_hash() to choose a nexthop
when an MPLS route has multiple nexthops.  While walking the MPLS label
stack, the hash routine caches hdr for the current label.  After finding
the bottom-of-stack label, it calls pskb_may_pull() before reading the
inner IP header.

If an skb is constructed with the inner IP header in nonlinear data and
insufficient tailroom in the linear head, pskb_may_pull() calls
pskb_expand_head() to replace the skb head and free the old one.  This
leaves hdr pointing to freed memory.  The IPv6 path can invalidate hdr
again when it performs a second pull for the larger header.

The issue was found through static analysis.  A reproducer sending a legal
Geneve packet through a bareudp/MPLS multipath setup triggered the same
KASAN report in 2 of 2 unpatched runs:

  BUG: KASAN: slab-use-after-free in mpls_select_multipath
  Read of size 1 at addr ffff88800ecc6e20 by task ksoftirqd/1/23

  Call Trace:
   mpls_select_multipath
   mpls_forward
   __netif_receive_skb_list_core
   netif_receive_skb_list_internal
   napi_complete_done
   gro_cell_poll
   __napi_poll
   net_rx_action

  Freed by task 23:
   kfree
   pskb_expand_head
   __pskb_pull_tail
   mpls_select_multipath

Reload hdr from the current skb head after each successful pull before
deriving the inner IPv4 or IPv6 header pointer.

## Affected

- `Linux >= 9f427a0e474a67b454420c131709600d44850486 < aa4fe0b450a461aa1162fe8375f5d28f4c957df8`
- `Linux >= 9f427a0e474a67b454420c131709600d44850486 < b1c0783b2facc398437ad8f8b86c636d7a78f8db`
- `Linux >= 9f427a0e474a67b454420c131709600d44850486 < bfaaff99238326166694354a63a76c02563f98b1`
- `Linux >= 9f427a0e474a67b454420c131709600d44850486 < d9640239827d6d0cb84263b590f7a4f1596c17eb`
- `Linux >= 9f427a0e474a67b454420c131709600d44850486 < fed638a248116b8a249bd4202d28e5934bdc65ad`
- `Linux >= 9f427a0e474a67b454420c131709600d44850486 < d82b90a38c2ca8a0694428eab0e9551c23f2447d`
- `Linux >= 9f427a0e474a67b454420c131709600d44850486 < 49d38c1b4390412f8950d33dfaee0ccbd17beb81`
- `Linux >= 9f427a0e474a67b454420c131709600d44850486 < 29e63b8d9fc150cc191b1c6eb7e16e1247e1b650`
- `Linux ad864d9fce0ec56cc8f6afe5c6a0e6d7f484b9eb`
- `Linux >= 4.9.8 < 4.10`
- `Linux 4.10`

## Remediation

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