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CVE-2026-53162
memcg: use round-robin victim selection in refill_stock
Published 2026-06-25 (4 months ago) by the Linux kernel CNA. Subsystem mm. Debian urgency: unimportant.
What to do, per Debian release
Debian's own status for CVE-2026-53162 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 | not affected | 6.12.113-1 | Nothing to do. trixie never shipped the vulnerable code. |
| Debian 14forky | fixed | 7.0.13-1 | Update the kernel and reboot. Fixed in 7.0.13-1. A running kernel keeps the old code until the machine restarts. |
| Debian unstablesid | fixed | 7.0.13-1 | Update the kernel and reboot. Fixed in 7.0.13-1. A running kernel keeps the old code until the machine restarts. |
The vulnerability
What the bug is
Harry Yoo reported that get_random_u32_below() is not safe to call in the nmi context and memcg charge draining can happen in nmi context. More specifically get_random_u32_below() is neither reentrant- nor NMI-safe: it acquires a per-cpu local_lock via local_lock_irqsave() on the batched_entropy_u32 state. An NMI that lands on a CPU mid-update of the ChaCha batch state and recurses into the random subsystem would corrupt that state. The memcg_stock local_trylock prevents re-entry on the percpu stock itself, but cannot protect an unrelated subsystem's per-cpu lock. Replace the random pick with a per-cpu round-robin counter stored in memcg_stock_pcp and serialized by the same local_trylock that already guards cached[] and nr_pages[]. No atomics, no random calls, no extra locks needed.
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.
mm/memcontrol.c
- What this is
- CONTROL GROUP - MEMORY RESOURCE CONTROLLER (MEMCG)MAINTAINERS section matched on mm/memcontrol.c · cgroups@vger.kernel.org · Maintained
Check it on the machine
grep -w CONFIG_MEMCG /boot/config-$(uname -r)Reads the booted kernel's own configuration, on the machine and nowhere else. =y is built in, =m is a module, and an is not set line means the code is not there.
Show whether Debian builds this, per release
Debian builds this code. Every release below compiles the affected file into the kernels it ships.
- bookworm, trixie, forky, sidy
- y
- built into the kernel image on every flavour - only a patch removes it
- Build switch
- CONFIG_MEMCG
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 kbuild Makefiles Debian linux-config packages
Signals
- Published
- 2026-06-25 (4 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
- 0.13%, higher than 2.1% of all CVEssource
- CISA KEV
- not listedthe KEV catalogue
- Debian urgency
- unimportantsource
- Subsystem
- mm
Upstream fixes
The versions the CNA records as introducing and fixing this, and the commit for each. source
| Introduced | Fixed in | Commit |
|---|---|---|
| 6.16 | 6.18.36 | 89bd8215e25a |
| 6.16 | 7.0.13 | 00731bd7e18f |
| 6.16 | 7.1 | c0cafe24d3f6 |
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 `refill_stock()` path is reached through local kernel activity such as memcg-accounted allocation/free paths and NMI-capable perf/BPF-style execution, not by unauthenticated network packets alone.
- AC:LAttack complexity, low
- An attacker can repeatedly drive memcg stock eviction and high-rate NMI/RNG activity; the race is timing-sensitive but both sides are influenceable from local execution.
- PR:LPrivileges required, low
- Reachability requires a local user context able to create or use memcg-accounted workloads and NMI-capable facilities such as perf/BPF or delegated equivalents, so low privileges are sufficient in a plausible deployment.
- UI:NUser interaction, none
- No separate victim action is required once the attacker can run the local workload and trigger the accounting/NMI activity.
- S:UScope, unchanged
- The corrupted state is inside the same kernel security authority; this is not a VM, IOMMU, or sandbox boundary escape by itself.
- C:HConfidentiality impact, high
- The bug corrupts per-CPU random subsystem batch state used for security-sensitive randomness, so confidentiality impact is high under the required higher-severity assumption.
- I:HIntegrity impact, high
- Corruption of kernel RNG state can undermine integrity of random-dependent kernel protections and identifiers, and the vulnerable interleaving includes state writes outside the intended entropy slot.
- A:HAvailability impact, high
- Kernel per-CPU state corruption in NMI context can lead to unpredictable kernel malfunction or hard failure, so availability impact is high.