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CVE-2026-53085
bpf: fix mm lifecycle in open-coded task_vma iterator
Published 2026-06-24 (4 months ago) by the Linux kernel CNA. Subsystem kernel/bpf. Debian urgency: unimportant.
What to do, per Debian release
Debian's own status for CVE-2026-53085 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 | 7.0.10-1 | Update the kernel and reboot. Fixed in 7.0.10-1. A running kernel keeps the old code until the machine restarts. |
| Debian unstablesid | fixed | 7.0.10-1 | Update the kernel and reboot. Fixed in 7.0.10-1. A running kernel keeps the old code until the machine restarts. |
The vulnerability
What the bug is
The open-coded task_vma iterator reads task->mm locklessly and acquires mmap_read_trylock() but never calls mmget(). If the task exits concurrently, the mm_struct can be freed as it is not SLAB_TYPESAFE_BY_RCU, resulting in a use-after-free. Safely read task->mm with a trylock on alloc_lock and acquire an mm reference. Drop the reference via bpf_iter_mmput_async() in _destroy() and error paths. bpf_iter_mmput_async() is a local wrapper around mmput_async() with a fallback to mmput() on !CONFIG_MMU. Reject irqs-disabled contexts (including NMI) up front. Operations used by _next() and _destroy() (mmap_read_unlock, bpf_iter_mmput_async) take spinlocks with IRQs disabled (pool->lock, pi_lock). Running from NMI or from a tracepoint that fires with those locks held could deadlock. A trylock on alloc_lock is used instead of the blocking task_lock() (get_task_mm) to avoid a deadlock when a softirq BPF program iterates a task that already holds its alloc_lock on the same CPU.
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/bpf/task_iter.c
- What this is
- BPF [ITERATOR]MAINTAINERS section matched on kernel/bpf/*iter.c · bpf@vger.kernel.org · Maintained
Check it on the machine
grep -wE 'CONFIG_BPF|CONFIG_BPF_SYSCALL' /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 switches
- CONFIG_BPF, CONFIG_BPF_SYSCALL
- Reads as
- all on means the file is compiled; any one off means it is not.
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
- 2026-06-24 (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
- 0.18%, higher than 6.6% of all CVEssource
- CISA KEV
- not listedthe KEV catalogue
- Debian urgency
- unimportantsource
- Subsystem
- kernel/bpf
Upstream fixes
The versions the CNA records as introducing and fixing this, and the commit for each. source
| Introduced | Fixed in | Commit |
|---|---|---|
| 6.7 | 6.12.91 | 239cec25a226 |
| 6.7 | 6.18.33 | d0862de7c866 |
| 6.7 | 7.0.10 | 43683bb28033 |
| 6.7 | 7.1 | d8e27d2d22b6 |
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 code is reached by a local attacker loading and running a BPF program through the bpf() syscall that invokes the open-coded task_vma iterator kfuncs. It is not reachable directly from remote network input.
- AC:LAttack complexity, low
- The triggering race is attacker-controllable by selecting or creating a target task and racing its exit while repeatedly invoking bpf_iter_task_vma_new/next/destroy. No rare external condition is required beyond normal BPF availability.
- PR:LPrivileges required, low
- kfunc calls require BPF privilege, but BPF tokens allow CAP_BPF/CAP_PERFMON-style checks in a delegated user namespace, making this reachable by a low-privileged local user in a reasonable user-namespace deployment. Without such delegation it would require init-namespace BPF privileges, but uncertainty is resolved toward the higher-severity PR:L.
- UI:NUser interaction, none
- Exploitation does not require a victim user action after the attacker has local execution. The attacker can load the BPF program and control the racing task lifecycle themselves.
- S:UScope, unchanged
- The vulnerability is in the kernel and impacts kernel-controlled memory and execution within the same security authority. This is a standard local kernel compromise path rather than a cross-scope VM or hardware boundary escape.
- C:HConfidentiality impact, high
- The bug is a use-after-free of mm_struct, which can allow freed kernel memory to be read or interpreted after reallocation while walking VMA state. Under the required conservative scoring rule, kernel UAF memory corruption supports high confidentiality impact.
- I:HIntegrity impact, high
- The stale mm_struct is used in locking and VMA iteration paths, causing writes to and operations on freed or reallocated kernel memory. This UAF is plausibly exploitable for arbitrary kernel memory corruption or code execution, so integrity impact is high.
- A:HAvailability impact, high
- Even without full exploitation, dereferencing and locking a freed mm_struct can readily crash or hang the kernel. A local attacker can repeat the trigger, so availability impact is high.