---
id: CVE-2024-57982
title: 'xfrm: state: fix out-of-bounds read during lookup'
summary: |-
  In the Linux kernel, the following vulnerability has been resolved:

  xfrm: state: fix out-of-bounds read during lookup

  lookup and resize can run in parallel.

  The xfrm_state_hash_generation seqlock ensures a retry, but the hash
  function…
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 >= c2f672fc94642bae96821a393f342edcfa9794a6 <
    80610185e9dd2ef7c0a4818a47390a8655b3dc27
  - >-
    Linux >= c2f672fc94642bae96821a393f342edcfa9794a6 <
    b86dc510308d7a8955f3f47a4fea4bef887653e4
  - >-
    Linux >= c2f672fc94642bae96821a393f342edcfa9794a6 <
    a16871c7832ea6435abb6e0b58289ae7dcb7e4fc
  - >-
    Linux >= c2f672fc94642bae96821a393f342edcfa9794a6 <
    dd4c2a174994238d55ab54da2545543d36f4e0d0
  - >-
    Linux >= c2f672fc94642bae96821a393f342edcfa9794a6 <
    e952837f3ddb0ff726d5b582aa1aad9aa38d024d
  - Linux 4.9
ssvc:
  exploitation: none
  automatable: 'no'
  technicalImpact: partial
  timestamp: '2025-10-01T19:31:46.705139Z'
published: '2025-02-27'
updated: '2026-10-30'
sourceUpdated: '2026-10-30T12:20:34.191Z'
source: CVEORG
sourceUrl: 'https://www.cve.org/CVERecord?id=CVE-2024-57982'
references:
  - url: 'https://git.kernel.org/stable/c/80610185e9dd2ef7c0a4818a47390a8655b3dc27'
  - url: 'https://git.kernel.org/stable/c/b86dc510308d7a8955f3f47a4fea4bef887653e4'
  - url: 'https://git.kernel.org/stable/c/a16871c7832ea6435abb6e0b58289ae7dcb7e4fc'
  - url: 'https://git.kernel.org/stable/c/dd4c2a174994238d55ab54da2545543d36f4e0d0'
  - url: 'https://git.kernel.org/stable/c/e952837f3ddb0ff726d5b582aa1aad9aa38d024d'
tags:
  - cve.org
epss: 0.00254
epssPercentile: 0.17128
ingestedAt: '2026-11-03T15:48:07.694Z'
---

## Overview

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

xfrm: state: fix out-of-bounds read during lookup

lookup and resize can run in parallel.

The xfrm_state_hash_generation seqlock ensures a retry, but the hash
functions can observe a hmask value that is too large for the new hlist
array.

rehash does:
  rcu_assign_pointer(net->xfrm.state_bydst, ndst) [..]
  net->xfrm.state_hmask = nhashmask;

While state lookup does:
  h = xfrm_dst_hash(net, daddr, saddr, tmpl->reqid, encap_family);
  hlist_for_each_entry_rcu(x, net->xfrm.state_bydst + h, bydst) {

This is only safe in case the update to state_bydst is larger than
net->xfrm.xfrm_state_hmask (or if the lookup function gets
serialized via state spinlock again).

Fix this by prefetching state_hmask and the associated pointers.
The xfrm_state_hash_generation seqlock retry will ensure that the pointer
and the hmask will be consistent.

The existing helpers, like xfrm_dst_hash(), are now unsafe for RCU side,
add lockdep assertions to document that they are only safe for insert
side.

xfrm_state_lookup_byaddr() uses the spinlock rather than RCU.
AFAICS this is an oversight from back when state lookup was converted to
RCU, this lock should be replaced with RCU in a future patch.

## Affected

- `Linux >= c2f672fc94642bae96821a393f342edcfa9794a6 < 80610185e9dd2ef7c0a4818a47390a8655b3dc27`
- `Linux >= c2f672fc94642bae96821a393f342edcfa9794a6 < b86dc510308d7a8955f3f47a4fea4bef887653e4`
- `Linux >= c2f672fc94642bae96821a393f342edcfa9794a6 < a16871c7832ea6435abb6e0b58289ae7dcb7e4fc`
- `Linux >= c2f672fc94642bae96821a393f342edcfa9794a6 < dd4c2a174994238d55ab54da2545543d36f4e0d0`
- `Linux >= c2f672fc94642bae96821a393f342edcfa9794a6 < e952837f3ddb0ff726d5b582aa1aad9aa38d024d`
- `Linux 4.9`

## Remediation

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