Linux Kernel up to 6.19.12 build_polexpire hard uninitialized pointer

CVSS Meta Temp Score
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CTI Interest Score
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4.9$0-$5k0.00

Summaryinfo

A vulnerability was found in Linux Kernel up to 6.1.168/6.6.134/6.12.81/6.18.22/6.19.12. It has been classified as critical. Affected by this vulnerability is the function build_polexpire. Performing a manipulation of the argument hard results in uninitialized pointer. This vulnerability is cataloged as CVE-2026-31664. There is no exploit available. Upgrading the affected component is recommended.

Detailsinfo

A vulnerability classified as critical has been found in Linux Kernel up to 6.1.168/6.6.134/6.12.81/6.18.22/6.19.12. This affects the function build_polexpire. The manipulation of the argument hard with an unknown input leads to a uninitialized pointer vulnerability. CWE is classifying the issue as CWE-824. The product accesses or uses a pointer that has not been initialized. The impact remains unknown. The summary by CVE is:

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().

The advisory is shared at git.kernel.org. This vulnerability is uniquely identified as CVE-2026-31664 since 03/09/2026. The exploitability is told to be difficult. Technical details are known, but no exploit is available. The price for an exploit might be around USD $0-$5k at the moment (estimation calculated on 06/04/2026).

The vulnerability scanner Nessus provides a plugin with the ID 310527 (Linux Distros Unpatched Vulnerability : CVE-2026-31664), which helps to determine the existence of the flaw in a target environment.

Upgrading to version 6.1.169, 6.6.135, 6.12.82, 6.18.23 or 6.19.13 eliminates this vulnerability. Applying the patch ac6985903db047eaff54db929e4bf6b06782788e/c221ed63a2769a0af8bd849dfe25740048f34ef4/eda30846ea54f8ed218468e5480c8305ca645e37/b1dfd6b27df35ef4f87825aa5f607378d23ff0f2/e1af65c669ebb1666c54576614c01a7f9ffcfff6/71a98248c63c535eaa4d4c22f099b68d902006d0 is able to eliminate this problem. The bugfix is ready for download at git.kernel.org. The best possible mitigation is suggested to be upgrading to the latest version.

The vulnerability is also documented in the databases at Tenable (310527) and EUVD (EUVD-2026-25557). If you want to get the best quality for vulnerability data then you always have to consider VulDB.

Productinfo

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CPE 2.3info

CPE 2.2info

CVSSv4info

VulDB Vector: 🔒
VulDB Reliability: 🔍

CVSSv3info

VulDB Meta Base Score: 5.0
VulDB Meta Temp Score: 4.9

VulDB Base Score: 4.6
VulDB Temp Score: 4.4
VulDB Vector: 🔒
VulDB Reliability: 🔍

NVD Base Score: 5.5
NVD Vector: 🔒

CVSSv2info

AVACAuCIA
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VulDB Base Score: 🔒
VulDB Temp Score: 🔒
VulDB Reliability: 🔍

Exploitinginfo

Class: Uninitialized pointer
CWE: CWE-824 / CWE-908
CAPEC: 🔒
ATT&CK: 🔒

Physical: Partially
Local: Yes
Remote: Partially

Availability: 🔒
Status: Not defined

EPSS Score: 🔒
EPSS Percentile: 🔒

Price Prediction: 🔍
Current Price Estimation: 🔒

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Nessus ID: 310527
Nessus Name: Linux Distros Unpatched Vulnerability : CVE-2026-31664

Threat Intelligenceinfo

Interest: 🔍
Active Actors: 🔍
Active APT Groups: 🔍

Countermeasuresinfo

Recommended: Upgrade
Status: 🔍

0-Day Time: 🔒

Upgrade: Kernel 6.1.169/6.6.135/6.12.82/6.18.23/6.19.13
Patch: ac6985903db047eaff54db929e4bf6b06782788e/c221ed63a2769a0af8bd849dfe25740048f34ef4/eda30846ea54f8ed218468e5480c8305ca645e37/b1dfd6b27df35ef4f87825aa5f607378d23ff0f2/e1af65c669ebb1666c54576614c01a7f9ffcfff6/71a98248c63c535eaa4d4c22f099b68d902006d0

Timelineinfo

03/09/2026 CVE reserved
04/24/2026 +45 days Advisory disclosed
04/24/2026 +0 days VulDB entry created
06/04/2026 +41 days VulDB entry last update

Sourcesinfo

Vendor: kernel.org

Advisory: git.kernel.org
Status: Confirmed

CVE: CVE-2026-31664 (🔒)
GCVE (CVE): GCVE-0-2026-31664
GCVE (VulDB): GCVE-100-359469
EUVD: 🔒

Entryinfo

Created: 04/24/2026 19:01
Updated: 06/04/2026 05:06
Changes: 04/24/2026 19:01 (59), 04/24/2026 19:35 (1), 04/28/2026 06:59 (2), 06/04/2026 05:06 (11)
Complete: 🔍
Cache ID: 216::103

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