# CVE-2026-31664

> Vulnerability · severity: **MEDIUM** (CVSS 5.5).

## Description

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().

## Key facts

- **CVE ID:** CVE-2026-31664
- **Published:** 2026-04-24
- **CVSS severity:** MEDIUM
- **CVSS base score:** 5.5
- **CWE codes:** NVD-CWE-noinfo

## Affected products

- `linux:linux_kernel`

## Primary sources

- NIST NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-31664

## Citation

> AI Analytics. CVE-2026-31664. Retrieved 2026-07-27 from https://api.ai-analytics.org/cve/CVE-2026-31664. Derived from NIST NVD. Licensed CC0.

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