---
id: CVE-2026-31664
title: 'xfrm: clear trailing padding in build_polexpire()'
summary: |-
  In the Linux kernel, the following vulnerability has been resolved:

  xfrm: clear trailing padding in build_polexpire()

  build_expire() clears the trailing padding bytes of struct
  xfrm_user_expire after setting the hard field via memset_a…
severity: none
vendor: Linux
product: Linux
affected:
  - >-
    Linux >= 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 <
    a5127501c8d30b5728791b1e340284ca5c9cc4bd
  - >-
    Linux >= 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 <
    e6f4ffe8596947a595c9544e73a73adcb0568b88
  - >-
    Linux >= 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 <
    ac6985903db047eaff54db929e4bf6b06782788e
  - >-
    Linux >= 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 <
    c221ed63a2769a0af8bd849dfe25740048f34ef4
  - >-
    Linux >= 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 <
    eda30846ea54f8ed218468e5480c8305ca645e37
  - >-
    Linux >= 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 <
    b1dfd6b27df35ef4f87825aa5f607378d23ff0f2
  - >-
    Linux >= 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 <
    e1af65c669ebb1666c54576614c01a7f9ffcfff6
  - >-
    Linux >= 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 <
    71a98248c63c535eaa4d4c22f099b68d902006d0
  - Linux 2.6.12
published: '2026-04-24'
updated: '2026-09-08'
sourceUpdated: '2026-09-08T08:47:55.898Z'
source: CVEORG
sourceUrl: 'https://www.cve.org/CVERecord?id=CVE-2026-31664'
references:
  - url: 'https://git.kernel.org/stable/c/a5127501c8d30b5728791b1e340284ca5c9cc4bd'
  - url: 'https://git.kernel.org/stable/c/e6f4ffe8596947a595c9544e73a73adcb0568b88'
  - url: 'https://git.kernel.org/stable/c/ac6985903db047eaff54db929e4bf6b06782788e'
  - url: 'https://git.kernel.org/stable/c/c221ed63a2769a0af8bd849dfe25740048f34ef4'
  - url: 'https://git.kernel.org/stable/c/eda30846ea54f8ed218468e5480c8305ca645e37'
  - url: 'https://git.kernel.org/stable/c/b1dfd6b27df35ef4f87825aa5f607378d23ff0f2'
  - url: 'https://git.kernel.org/stable/c/e1af65c669ebb1666c54576614c01a7f9ffcfff6'
  - url: 'https://git.kernel.org/stable/c/71a98248c63c535eaa4d4c22f099b68d902006d0'
tags:
  - cve.org
epss: 0.00171
epssPercentile: 0.05738
ingestedAt: '2026-09-08T15:33:26.989Z'
---

## Overview

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

xfrm: clear trailing padding in build_polexpire()

build_expire() clears the trailing padding bytes of struct
xfrm_user_expire after setting the hard field via memset_after(),
but the analogous function build_polexpire() does not do this for
struct xfrm_user_polexpire.

The padding bytes after the __u8 hard field are left
uninitialized from the heap allocation, and are then sent to
userspace via netlink multicast to XFRMNLGRP_EXPIRE listeners,
leaking kernel heap memory contents.

Add the missing memset_after() call, matching build_expire().

## Affected

- `Linux >= 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 < a5127501c8d30b5728791b1e340284ca5c9cc4bd`
- `Linux >= 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 < e6f4ffe8596947a595c9544e73a73adcb0568b88`
- `Linux >= 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 < ac6985903db047eaff54db929e4bf6b06782788e`
- `Linux >= 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 < c221ed63a2769a0af8bd849dfe25740048f34ef4`
- `Linux >= 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 < eda30846ea54f8ed218468e5480c8305ca645e37`
- `Linux >= 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 < b1dfd6b27df35ef4f87825aa5f607378d23ff0f2`
- `Linux >= 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 < e1af65c669ebb1666c54576614c01a7f9ffcfff6`
- `Linux >= 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 < 71a98248c63c535eaa4d4c22f099b68d902006d0`
- `Linux 2.6.12`

## Remediation

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