CVE-2026-31541 tracing: Fix trace_marker copy link list updates

What is CVE-2026-31541?

CVE-2026-31541 is a high-severity use after free 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:

tracing: Fix trace_marker copy link list updates

When the "copy_trace_marker" option is enabled for an instance, anything written into /sys/kernel/tracing/trace_marker is also copied into that instances buffer. When the option is set, that instance's trace_array descriptor is added to the marker_copies link list. This list is protected by RCU, as all iterations uses an RCU protected list traversal.

When the instance is deleted, all the flags that were enabled are cleared. This also clears the copy_trace_marker flag and removes the trace_array descriptor from the list.

The issue is after the flags are called, a direct call to update_marker_trace() is performed to clear the flag. This function returns true if the state of the flag changed and false otherwise. If it returns true here, synchronize_rcu() is called to make sure all readers see that its removed from the list.

But since the flag was already cleared, the state does not change and the synchronization is never called, leaving a possible UAF bug.

Move the clearing of all flags below the updating of the copy_trace_marker option which then makes sure the synchronization is performed.

Also use the flag for checking the state in update_marker_trace() instead of looking at if the list is empty.

Weakness: CWE-416

Which versions are affected by CVE-2026-31541?

It affects 1 product.

Products include Linux kernel.

How do I fix CVE-2026-31541?

Apply the vendor's patch.

Upgrade to the fixed version. These bugs are found with fuzzing and sanitisers and avoided by memory-safe languages. More about Use after free.

Is CVE-2026-31541 being exploited?

There is no known exploitation of CVE-2026-31541 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 BELL-CVE-2026-31541, DEBIAN-CVE-2026-31541, GHSA-mfcj-fwjx-5q54, UBUNTU-CVE-2026-31541.