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Linux KernelOperating system · Linux

CVE-2026-52980

MEDIUM · 5.5 CVSS v3.1 Published 2026-06-24
Fix available
A fix is available. Upgrade to 6.12.91 / 6.18.33 or later.
See remediation →
57/100
Remediation priority · Elevated
Zero-click 8 weeks old

Official description Straight from the sourceThe vendor's or NVD's own wording, published unedited. Authoritative, but often terse — it says what broke, rarely what to do.

NVD · unedited
In the Linux kernel, the following vulnerability has been resolved: sched/fair: Clear rel_deadline when initializing forked entities A yield-triggered crash can happen when a newly forked sched_entity enters the fair class with se->rel_deadline unexpectedly set. The failing sequence is: 1. A task is forked while se->rel_deadline is still set. 2. __sched_fork() initializes vruntime, vlag and other sched_entity state, but does not clear rel_deadline. 3. On the first enqueue, enqueue_entity() calls place_entity(). 4. Because se->rel_deadline is set, place_entity() treats se->deadline as a relative deadline and converts it to an absolute deadline by adding the current vruntime. 5. However, the forked entity's deadline is not a valid inherited relative deadline for this new scheduling instance, so the conversion produces an abnormally large deadline. 6. If the task later calls sched_yield(), yield_task_fair() advances se->vruntime to se->deadline. 7. The inflated vruntime is then used by the following enqueue path, where the vruntime-derived key can overflow when multiplied by the entity weight. 8. This corrupts cfs_rq->sum_w_vruntime, breaks EEVDF eligibility calculation, and can eventually make all entities appear ineligible. pick_next_entity() may then return NULL unexpectedly, leading to a later NULL dereference. A captured trace shows the effect clearly. Before yield, the entity's vruntime was around: 9834017729983308 After yield_task_fair() executed: se->vruntime = se->deadline the vruntime jumped to: 19668035460670230 and the deadline was later advanced further to: 19668035463470230 This shows that the deadline had already become abnormally large before yield_task_fair() copied it into vruntime. rel_deadline is only meaningful when se->deadline really carries a relative deadline that still needs to be placed against vruntime. A freshly forked sched_entity should not inherit or retain this state. Clear se->rel_deadline in __sched_fork(), together with the other sched_entity runtime state, so that the first enqueue does not interpret the new entity's deadline as a stale relative deadline.

Technical summary Written by usOur analysis, written from the advisory, the CVSS vector and the affected-version data. It adds context the advisory leaves out, and never invents facts that are not in the source.

dbcve analysis · high confidence

A race condition in the Linux kernel's CFS scheduler allows a forked sched_entity to retain a stale rel_deadline value. When __sched_fork() initializes a new entity, it fails to clear rel_deadline, causing place_entity() to misinterpret the deadline as a relative deadline and inflate it to an abnormally large absolute deadline. If the task later yields, the inflated deadline is copied to vruntime, corrupting sum_w_vruntime and potentially causing pick_next_entity() to return NULL.

MitigationApply the kernel patch that clears se->rel_deadline in __sched_fork() during sched_entity initialization, ensuring forked tasks do not inherit stale relative deadline state.

Verify against the referenced sources before acting — the references below are authoritative for this CVE, this summary is not.

Affected products & versions What the vendor confirmedThe version ranges the vendor confirmed as vulnerable. If your version sits inside a range here, treat yourself as exposed until you have upgraded.

NVD · CPE data
Linux KernelOperating system
Affected:>= 6.12, < 6.12.91>= 6.13, < 6.18.33>= 6.19, < 7.0.10= 7.1

CVSS breakdown How the score is builtThe industry scoring standard. It rates how the flaw is reached, what it takes to exploit, and what an attacker gains — the score is derived from those, not the other way round.

From the vector
Attack vector
Local
Complexity
Low
Privileges
Low
User interaction
None
Scope
Unchanged
Confidentiality
None
Integrity
None
Availability
High

CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H

Am I affected? How to checkSteps we derive from the advisory and the affected-version data, so you can decide whether this CVE reaches your setup. They are a guide, not a scan — your own configuration is the authority.

dbcve checks

Work through these to decide whether this CVE applies to you.

  1. Identify your kernel version
    Run 'uname -r' or 'cat /proc/version' to get the running kernel version
    Affected if The version falls within >= 6.12 and < 6.12.91, OR >= 6.13 and < 6.18.33, OR >= 6.19 and < 7.0.10, OR equals 7.1
  2. Confirm CFS scheduler is in use
    Check /sys/kernel/debug/sched/features for CFS-related settings, or verify 'CONFIG_CFS_BANDWIDTH' is set in /boot/config-$(uname -r)
    Affected if The system uses the CFS scheduler (default for most Linux distributions)
  3. Monitor for scheduler NULL pointer errors
    Review kernel logs with 'dmesg | grep -i "NULL"' or 'journalctl -k' for messages containing 'pick_next_entity' returning NULL, or kernel oops/panic traces
    Affected if Kernel logs show NULL pointer dereferences in scheduler code paths related to pick_next_entity
  4. Check for abnormal vruntime or deadline values
    Inspect /proc/[pid]/sched for tasks showing unusually large 'deadline' or 'vruntime' values compared to other tasks of similar runtime
    Affected if Tasks exhibit abnormally large deadline or vruntime values suggesting corruption
  5. Detect fork-heavy workloads triggering the race
    Monitor for processes performing rapid fork operations (e.g., 'ps -o ppid,pid,comm' and look for processes with many children, or use 'pidstat -t 1' to observe fork rates)
    Affected if The system runs workloads that rapidly fork processes, increasing likelihood of hitting the race condition

You are affected if your kernel version is in the vulnerable range AND you observe scheduler anomalies such as pick_next_entity NULL returns or tasks with corrupted deadline/vruntime values, especially under fork-heavy workloads.

Generated from the published advisory. Verify against your own configuration.

Check your environment

Paste your version and any relevant configuration and it will be compared against the affected criteria above. Do not include secrets or credentials.

AI-assisted, checked against the advisory. Informational, not a guarantee.

Remediation Closing itWhat it takes to close this. Where a vendor fix exists we point at it; where none exists we say so plainly, and can build one. Effort estimates are scoped from the advisory, not from your codebase.

dbcve · scoped
Upgrade available Upgrade to 6.12.91 / 6.18.33 / 7.0.10 or later
Fixed in 6.12.916.18.337.0.10
Interim mitigation

Apply the kernel patch that clears se->rel_deadline in __sched_fork() during sched_entity initialization, ensuring forked tasks do not inherit stale relative deadline state.

Recommended fix High confidence

Linux kernel 6.12.91, 6.18.33, or 7.0.10 (depending on which branch you are on)

  1. 1. Identify the current running kernel version using `uname -r` or `cat /proc/version`
  2. 2. Determine the appropriate upgrade target based on current version: for 6.12.x upgrade to 6.12.91, for 6.13.x-6.18.x upgrade to 6.18.33, for 6.19.x upgrade to 7.0.10
  3. 3. Update the kernel package using the distribution's package manager (e.g., `apt-get update && apt-get upgrade` for Debian/Ubuntu, `yum update` for RHEL/CentOS, or `dnf upgrade` for Fedora)
  4. 4. Reboot the system to load the new kernel
  5. 5. Verify the fix is applied by checking that `se->rel_deadline` is now cleared in `__sched_fork()` function in kernel/sched/fair.c
Caveat Kernel upgrades may introduce regressions; ensure compatibility with custom drivers or modules before rebooting

Generated from the published advisory — verify against the referenced sources before acting.

Fix this in Linux Kernel Scoped from the published advisory
  • Consultation2.0 h
  • Implementation1.0 h
  • Testing3.0 h
  • Review / QA1.0 h
7.0 hours of engineering $1,210
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References Go to the primary sourcePrimary sources — vendor advisories, patches and trackers. Where our summary and a reference disagree, the reference wins.

Primary sources

Practitioner notes

Contributed

Peer-ranked notes from engineers who’ve handled CVE-2026-52980 in production — separate from our analysis above.

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