Linux Kernel up to 6.6.122/6.12.68/6.18.8 perf is_user_task null pointer dereference

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Summaryinfo

A vulnerability was found in Linux Kernel up to 6.6.122/6.12.68/6.18.8. It has been classified as critical. This affects the function is_user_task of the component perf. Performing a manipulation results in null pointer dereference. This vulnerability is cataloged as CVE-2026-23159. There is no exploit available. Upgrading the affected component is recommended.

Detailsinfo

A vulnerability was found in Linux Kernel up to 6.6.122/6.12.68/6.18.8. It has been classified as critical. This affects the function is_user_task of the component perf. The manipulation with an unknown input leads to a null pointer dereference vulnerability. CWE is classifying the issue as CWE-476. A NULL pointer dereference occurs when the application dereferences a pointer that it expects to be valid, but is NULL, typically causing a crash or exit. This is going to have an impact on availability. The summary by CVE is:

In the Linux kernel, the following vulnerability has been resolved: perf: sched: Fix perf crash with new is_user_task() helper In order to do a user space stacktrace the current task needs to be a user task that has executed in user space. It use to be possible to test if a task is a user task or not by simply checking the task_struct mm field. If it was non NULL, it was a user task and if not it was a kernel task. But things have changed over time, and some kernel tasks now have their own mm field. An idea was made to instead test PF_KTHREAD and two functions were used to wrap this check in case it became more complex to test if a task was a user task or not[1]. But this was rejected and the C code simply checked the PF_KTHREAD directly. It was later found that not all kernel threads set PF_KTHREAD. The io-uring helpers instead set PF_USER_WORKER and this needed to be added as well. But checking the flags is still not enough. There's a very small window when a task exits that it frees its mm field and it is set back to NULL. If perf were to trigger at this moment, the flags test would say its a user space task but when perf would read the mm field it would crash with at NULL pointer dereference. Now there are flags that can be used to test if a task is exiting, but they are set in areas that perf may still want to profile the user space task (to see where it exited). The only real test is to check both the flags and the mm field. Instead of making this modification in every location, create a new is_user_task() helper function that does all the tests needed to know if it is safe to read the user space memory or not. [1] https://lore.kernel.org/all/[email protected]/

The advisory is shared at git.kernel.org. This vulnerability is uniquely identified as CVE-2026-23159 since 01/13/2026. The exploitability is told to be difficult. Technical details are known, but no exploit is available.

The vulnerability scanner Nessus provides a plugin with the ID 299151 (Linux Distros Unpatched Vulnerability : CVE-2026-23159), which helps to determine the existence of the flaw in a target environment.

Upgrading to version 6.6.123, 6.12.69 or 6.18.9 eliminates this vulnerability. Applying the patch d84a4836dc246b7dc244e46a08ff992956b68db0/5aac392fcd3d981d7997f1a0766829e1afdeac2e/a28fce0365e1cb9cb8c04c893b9334e5ca9d9f1c/76ed27608f7dd235b727ebbb12163438c2fbb617 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 (299151) and CERT Bund (WID-SEC-2026-0421). If you want to get the best quality for vulnerability data then you always have to consider VulDB.

Affected

  • Google Container-Optimized OS
  • Debian Linux
  • Google Cloud Platform
  • Amazon Linux 2
  • Red Hat Enterprise Linux
  • Ubuntu Linux
  • SUSE Linux
  • Oracle Linux
  • SUSE openSUSE
  • RESF Rocky Linux
  • Open Source Linux Kernel
  • IBM QRadar SIEM

Productinfo

Type

Vendor

Name

Version

License

Website

CPE 2.3info

CPE 2.2info

CVSSv4info

VulDB Vector: 🔒
VulDB Reliability: 🔍

CVSSv3info

VulDB Meta Base Score: 5.1
VulDB Meta Temp Score: 5.0

VulDB Base Score: 4.8
VulDB Temp Score: 4.6
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: Null pointer dereference
CWE: CWE-476 / CWE-404
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: 299151
Nessus Name: Linux Distros Unpatched Vulnerability : CVE-2026-23159

Threat Intelligenceinfo

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

Countermeasuresinfo

Recommended: Upgrade
Status: 🔍

0-Day Time: 🔒

Upgrade: Kernel 6.6.123/6.12.69/6.18.9
Patch: d84a4836dc246b7dc244e46a08ff992956b68db0/5aac392fcd3d981d7997f1a0766829e1afdeac2e/a28fce0365e1cb9cb8c04c893b9334e5ca9d9f1c/76ed27608f7dd235b727ebbb12163438c2fbb617

Timelineinfo

01/13/2026 CVE reserved
02/14/2026 +32 days Advisory disclosed
02/14/2026 +0 days VulDB entry created
05/05/2026 +80 days VulDB entry last update

Sourcesinfo

Vendor: kernel.org

Advisory: git.kernel.org
Status: Confirmed

CVE: CVE-2026-23159 (🔒)
GCVE (CVE): GCVE-0-2026-23159
GCVE (VulDB): GCVE-100-346029
CERT Bund: WID-SEC-2026-0421 - Linux Kernel: Mehrere Schwachstellen

Entryinfo

Created: 02/14/2026 17:57
Updated: 05/05/2026 16:52
Changes: 02/14/2026 17:57 (59), 02/17/2026 02:07 (2), 02/19/2026 10:55 (1), 03/09/2026 11:50 (7), 03/19/2026 04:56 (11), 04/13/2026 01:14 (1), 05/05/2026 16:52 (1)
Complete: 🔍
Cache ID: 216::103

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