CVE-2026-99234
Received Received - Intake

Memory Leak in Linux Kernel Tracing

Publication date: 2026-11-02

Last updated on: 2026-11-02

Assigner: kernel.org

Description
In the Linux kernel, the following vulnerability has been resolved: tracing: Unregister field variable histograms when the command fails An action that names a field on another event needs that field as a variable, so create_field_var_hist() registers a second hist trigger on that event to provide it, and records it in target_hist_data->field_var_hists[]. If a later part of the same command fails, create_actions() returns an error and event_hist_trigger_parse() jumps to out_free. The write fails with -EINVAL and sched_switch gets no trigger, but: # echo 'hist:keys=pid:ts0=common_timestamp.usecs' >> \ events/sched/sched_waking/trigger # echo 'my_synth u64 lat; int a; int b' >> synthetic_events # echo 'hist:keys=next_pid:wakeup_lat=common_timestamp.usecs-$ts0:\ onmatch(sched.sched_waking).my_synth($wakeup_lat,prio,nosuchfld)'\ >> events/sched/sched_switch/trigger # cat events/sched/sched_waking/trigger hist:keys=pid:vals=hitcount:ts0=common_timestamp.usecs:sort=hitcount:size=2048:clock=global [active] hist:keys=pid:vals=hitcount:synthetic_prio=prio:sort=hitcount:size=2048 [active] The second histogram is the one created for 'prio'. It is still active and still counting. out_free reaches destroy_field_var_hists(), which frees the field_var_hists[] entries, but never unregister_field_var_hists(), which is what removes the triggers and runs only from event_hist_trigger_free(). The entry is freed and the trigger is left with nothing tracking it. Unregister the field variable histograms in out_free as well, and record each one as soon as its trigger is registered rather than after the lookup that follows it, so no exit can leave a registered trigger untracked. The entry then belongs to field_var_hists[] and is released by destroy_field_var_hists(), so freeing it on that exit would be a double free.

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Meta Information

Published
2026-11-02
Last Modified
2026-11-02
Generated
2026-11-02
AI Q&A
2026-11-02
EPSS Evaluated
N/A
NVD
CVE-2026-99234

Affected Vendors & Products

Showing 9 associated CPEs
Vendor Product Version / Range
Linux Linux 02205a6752f223779a1b0e9e8ffacbea6e717851
Linux Linux 02205a6752f223779a1b0e9e8ffacbea6e717851
Linux Linux 02205a6752f223779a1b0e9e8ffacbea6e717851
Linux Linux 02205a6752f223779a1b0e9e8ffacbea6e717851
Linux Linux 02205a6752f223779a1b0e9e8ffacbea6e717851
Linux Linux 02205a6752f223779a1b0e9e8ffacbea6e717851
Linux Linux 02205a6752f223779a1b0e9e8ffacbea6e717851
Linux Linux 02205a6752f223779a1b0e9e8ffacbea6e717851
Linux Linux 4.17

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Exploitability

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CWE ID Description
CWE-UNKNOWN

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Executive Summary

This vulnerability in the Linux kernel involves improper handling of field variable histograms during command failures in the tracing subsystem. When a command fails after creating a histogram for a field variable, the cleanup process does not properly unregister the histogram trigger. This leaves the trigger active and counting events even though it should be removed, potentially causing incorrect data tracking and resource leaks.

Detection Guidance

This vulnerability is specific to the Linux kernel's tracing subsystem and requires kernel-level inspection. Check for active histogram triggers with leftover field variables using commands like 'cat /sys/kernel/debug/tracing/events/sched/sched_waking/trigger' or 'cat /sys/kernel/debug/tracing/events/sched/sched_switch/trigger'. Look for unexpected active triggers or synthetic events that may indicate improper cleanup.

Impact Analysis

This vulnerability could lead to incorrect data collection in kernel tracing, causing unreliable performance metrics or security monitoring. It may result in resource leaks where active triggers are not properly cleaned up, potentially affecting system stability or performance over time.

Compliance Impact

This vulnerability does not directly affect compliance with GDPR, HIPAA, or similar standards. It is a Linux kernel tracing subsystem issue that could lead to memory leaks or resource exhaustion if exploited, but there is no evidence it impacts data protection or privacy requirements.

Mitigation Strategies

Update your Linux kernel to a patched version that includes the fix for this issue. If immediate patching is not possible, avoid creating complex histogram triggers that involve field variables or synthetic events until the kernel is updated. Monitor kernel logs for errors related to tracing subsystem failures.

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