CVE-2026-23319

High

In the Linux kernel, the following vulnerability has been resolved: bpf: Fix a UAF issue in bpf_trampoline_link_cgroup_shim The root cause of this bug is that when 'bpf_link_put' reduces the refcount of 'shim_link->link.link' to zero, the resource is considered released but may still be referenced via 'tr->progs_hlist' in 'cgroup_shim_find'. The actual cleanup of 'tr->progs_hlist' in 'bpf_shim_tramp_link_release' is deferred. During this window, another process can cause a use-after-free via 'bpf_trampoline_link_cgroup_shim'. Based on Martin KaFai Lau's suggestions, I have created a simple patch. To fix this: Add an atomic non-zero check in 'bpf_trampoline_link_cgroup_shim'. Only increment the refcount if it is not already zero. Testing: I verified the fix by adding a delay in 'bpf_shim_tramp_link_release' to make the bug easier to trigger: static void bpf_shim_tramp_link_release(struct bpf_link *link) { /* ... */ if (!shim_link->trampoline) return; + msleep(100); WARN_ON_ONCE(bpf_trampoline_unlink_prog(&shim_link->link, shim_link->trampoline, NULL)); bpf_trampoline_put(shim_link->trampoline); } Before the patch, running a PoC easily reproduced the crash(almost 100%) with a call trace similar to KaiyanM's report. After the patch, the bug no longer occurs even after millions of iterations.

Package Linux Kernel
Published 2026-03-25
Last modified 2026-04-23
CVSS version 3.1
Patch available
Yes

CVSS 3.1 score

7.8

out of 10
High
Attack Vector
Local
Attack Complexity
Low
Privileges Required
Low
User Interaction
None
Scope
Unchanged
Confidentiality
High
Integrity
High
Availability
High
Vector string
CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H

Weakness type

CWE-416

CVE-2026-23319 is a Use After Free vulnerability

What is Use After Free?

The product references memory after it has been freed, which may cause it to crash, use unexpected values, or execute code. Learn more on MITRE CWE

Affected versions

Linux kernel versions 6.0 and later are affected. Fixed in 6.1.167, 6.6.130, 6.12.77, 6.18.17, 6.19.7, 7.0 and their respective stable series.

Affected from
≥ 6.0
Fixed in
✓ 6.1.167 6.1.x ✓ 6.6.130 6.6.x ✓ 6.12.77 6.12.x ✓ 6.18.17 6.18.x ✓ 6.19.7 6.19.x ✓ 7.0

References

The following references provide additional information about CVE-2026-23319 including vendor advisories, patch commits, exploit details, and third-party analysis. Links are sourced from the NIST NVD database.

6 patch commits total View all on NVD

Frequently asked questions

  • What is CVE-2026-23319?

    CVE-2026-23319 is a High severity Linux kernel vulnerability with a CVSS score of 7.8 out of 10 , classified as an Use After Free flaw (CWE-416) . It affects Linux kernel versions from 6.0 onward and has been patched in 6.1.167, 6.6.130, 6.12.77 and others. CVE-2026-23319 has not been confirmed as actively exploited and is not listed in the CISA KEV catalog.

  • What is the CVSS score for CVE-2026-23319?

    CVE-2026-23319 has a CVSS score of 7.8 out of 10, rated High severity (CVSS 3.1). The vector string is CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H .

  • Is there a patch available for CVE-2026-23319?

    Yes — CVE-2026-23319 has been patched. Fixed versions include 6.1.167, 6.6.130, 6.12.77 and others. If you are running Linux kernel 6.0 or later up to the fix versions, apply the relevant patch for your kernel branch.

  • Is CVE-2026-23319 actively exploited?

    No — CVE-2026-23319 has not been confirmed as actively exploited. It is not listed in the CISA Known Exploited Vulnerabilities (KEV) catalog.

  • What is Use After Free (CWE-416)?

    The product references memory after it has been freed, which may cause it to crash, use unexpected values, or execute code. View CWE-416 on MITRE CWE →

Back to
All CVEs
View on
NVD / NIST