CVE-2026-31664 xfrm: clear trailing padding in build_polexpire()

What is CVE-2026-31664?

CVE-2026-31664 is a medium-severity vulnerability in Linux kernel, published on 24 Apr 2026. It can only be exploited from the same machine or local network, with no action from the victim.

Official 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().

Which versions are affected by CVE-2026-31664?

It affects 1 product.

Products include Linux kernel.

How do I fix CVE-2026-31664?

Apply the vendor's patch.

Is CVE-2026-31664 being exploited?

There is no known exploitation of CVE-2026-31664 in the wild and no public exploit code.

Other vulnerabilities in Linux kernel

• CVE-2026-53266 Linux Kernel Out-of-Bounds Write Exploited High 8.8
• CVE-2013-6282 Linux Kernel Improper Input Validation Exploited High 8.8
• CVE-2022-0185 Linux Kernel Heap-Based Buffer Overflow Exploited High 8.4
• CVE-2013-2094 Linux Kernel Privilege Escalation Exploited High 8.4
• CVE-2026-53362 Linux Kernel Unspecified Exploited High 7.8

All Linux kernel vulnerabilities

Sources

• CVE record
• NVD
• OSV
• GitHub advisory
• How this page is made

Also known as AZL-83873, BELL-CVE-2026-31664, DEBIAN-CVE-2026-31664, GHSA-5fvv-6wpc-9mr7, ROOT-OS-DEBIAN-11-CVE-2026-31664, ROOT-OS-DEBIAN-12-CVE-2026-31664 and 3 more.