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CVE-2026-64226
sched_ext: Avoid UAF in scx_root_enable_workfn() init failure path
Published 2026-07-24 (3 months ago) by the Linux kernel CNA. Subsystem kernel/sched. Debian urgency: unimportant.
What to do, per Debian release
Debian's own status for CVE-2026-64226 in every release this site tracks, and what each one means in practice. Every status below is the one the Debian Security Team publishes for this CVE. source
| Release | Status | Version | What this means |
|---|---|---|---|
| Debian 12bookworm | not affected | 6.1.190-1 | Nothing to do. bookworm never shipped the vulnerable code. |
| Debian 13trixie | fixed | 6.12.94-1 | Update the kernel and reboot. Fixed in 6.12.94-1. A running kernel keeps the old code until the machine restarts. |
| Debian 14forky | fixed | 7.0.12-1 | Update the kernel and reboot. Fixed in 7.0.12-1. A running kernel keeps the old code until the machine restarts. |
| Debian unstablesid | fixed | 7.0.12-1 | Update the kernel and reboot. Fixed in 7.0.12-1. A running kernel keeps the old code until the machine restarts. |
The vulnerability
What the bug is
In scx_root_enable_workfn(), put_task_struct(p) is called before scx_error() dereferences p->comm and p->pid. If the iterator's reference is the last drop, the task is freed synchronously and the deref becomes a UAF. Move put_task_struct() past scx_error().
Where it lives
The fix touches these files. If the subsystem is one you do not use, the practical exposure is lower, though the package is still the vulnerable one.
kernel/sched/ext.c
- What this is
- SCHEDULERMAINTAINERS section matched on kernel/sched/ · linux-kernel@vger.kernel.org · Maintained
Show whether Debian builds this, per release
Not established. This site could not find the build rule for the affected file in the kernel trees Debian ships, so it has no answer about whether Debian compiles this code. Read that as unknown, never as absent.
- bookworm, trixie, forky, sid?
- ?
- not established - no Makefile entry for the affected file
Where a release above reads "not established", no build rule for the affected file was found in that release's kernel tree. That is a gap in this lookup, not a finding that the code is absent.
From the configuration Debian publishes for every kernel flavour it builds. It covers only the architectures Debian ships a linux-config package for, and nothing about a kernel you built yourself. Debian's own status above stays authoritative about the source package.MAINTAINERS
Signals
- Published
- 2026-07-24 (3 months ago)source
- CVSS
- 7.8 high
CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:Hsource recompute it - Attack vector
- local (AV:L)source
- EPSS
- 0.18%, higher than 6.6% of all CVEssource
- CISA KEV
- not listedthe KEV catalogue
- Debian urgency
- unimportantsource
- Subsystem
- kernel/sched
Upstream fixes
The versions the CNA records as introducing and fixing this, and the commit for each. source
| Introduced | Fixed in | Commit |
|---|---|---|
| 6.12 | 6.12.92 | cf3969419018 |
| 6.12 | 6.18.34 | 45c7c4e3db8b |
| 6.12 | 7.0.11 | 57e19ba3f58a |
| 6.12 | 7.1 | 9a415cc53711 |
Why the CNA scored it this way
Quoted from the kernel CNA's own scoring file, word for word. A highlighted metric carries the most severe value CVSS v3.1 defines for it, which is what pushes the score up. source
- AV:LAttack vector, local
- The vulnerable enable path is reached locally through bpf() struct_ops map preparation and BPF_LINK_CREATE, which invokes scx_enable() and scx_root_enable_workfn().
- AC:LAttack complexity, low
- The attacker can make ops.init_task() return an error for a selected task while concurrently causing that task to exit, controlling both sides of the race and allowing repeated attempts.
- PR:LPrivileges required, low
- Although ordinary attachment requires init-namespace CAP_BPF and CAP_PERFMON, BPF tokens can delegate the necessary struct_ops permissions to a non-init user namespace. Under the highest defensible deployment scenario, this is reachable by a locally authorized but non-administrative user.
- UI:NUser interaction, none
- The attacker can attach the scheduler and coordinate the target task's exit without requiring another user to take any action.
- S:UScope, unchanged
- The vulnerable sched_ext code and the affected kernel memory and execution context belong to the same kernel security authority.
- C:HConfidentiality impact, high
- The freed task_struct is dereferenced through p->comm as a string and p->pid, potentially exposing reclaimed or adjacent slab contents through the sched_ext diagnostic buffer. Consistent with the required UAF guidance, confidentiality impact is High.
- I:HIntegrity impact, high
- The access occurs after a task_struct slab object has been freed and can be influenced through heap reuse and spraying. Applying the required higher-severity treatment for UAF conditions, potential memory-corruption and control-flow impact warrants High.
- A:HAvailability impact, high
- The stale string dereference can cause a KASAN failure, invalid-memory access, kernel oops, or panic, and the attacker can repeat the controlled failure-and-exit sequence.