Look up another CVE · open CVE-2026-64251 in the interactive tracker
CVE-2026-64251
pwrseq: core: fix use-after-free in pwrseq_debugfs_seq_next()
Published 2026-07-24 (3 months ago) by the Linux kernel CNA. Subsystem drivers/power. Debian urgency: unimportant.
What to do, per Debian release
Debian's own status for CVE-2026-64251 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 | 6.12.95-1 | Update the kernel and reboot. Fixed in 6.12.95-1. A running kernel keeps the old code until the machine restarts. |
| Debian 14forky | fixed | 7.1.3-1 | Update the kernel and reboot. Fixed in 7.1.3-1. A running kernel keeps the old code until the machine restarts. |
| Debian unstablesid | fixed | 7.1.3-1 | Update the kernel and reboot. Fixed in 7.1.3-1. A running kernel keeps the old code until the machine restarts. |
The vulnerability
What the bug is
pwrseq_debugfs_seq_next() declares 'next' with __free(put_device), which causes put_device() to be called on the returned pointer when the variable goes out of scope. This results in a use-after-free since the seq_file framework receives a pointer whose reference has already been dropped. Simply removing __free(put_device) would fix the UAF but would leak the reference acquired by bus_find_next_device(), as stop() only calls up_read(&pwrseq_sem) and never releases the device reference. Fix this by making the reference counting consistent across all seq_file callbacks, matching the standard pattern used by PCI and SCSI: - start(): use get_device() so it returns a referenced pointer. - next(): explicitly put_device(curr) to release the previous device's reference (no NULL check needed - the seq_file framework only calls next() while the previous return was non-NULL). - stop(): put_device(data) to release the last iterated device's reference, with a NULL guard since stop() may be called with NULL when start() returned NULL or next() reached end-of-sequence.
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.
drivers/power/sequencing/core.c
- What this is
- POWER SEQUENCINGMAINTAINERS section matched on drivers/power/sequencing/ · linux-pm@vger.kernel.org · Maintained
- Kernel module
- pwrseq_core
Check it on the machine
grep -w CONFIG_POWER_SEQUENCING /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.
lsmod | grep -w pwrseq_corePrints a line if that module is loaded right now, and nothing if it is not. One that is not loaded can still be loaded later by anything that needs it.
Show whether Debian builds this, per release
Debian builds this, but not on every flavour. At least one release below builds the code on some of its kernel flavours and not on others, so the answer depends on the architecture and flavour installed. The build rule could not be established for 1 release, so nothing is claimed about those.
- bookworm?
- trixieMnot built on amd64/amd64, amd64/cloud-amd64, amd64/rt/amd64, arm64/cloud-arm64, armel/rpi, armhf/armmp, armhf/armmp-lpae, armhf/rt/armmp, ppc64el/powerpc64le, ppc64el/powerpc64le-64k, riscv64/riscv64, s390x/s390x
- forky, sidYnot built on amd64/amd64, amd64/cloud-amd64, amd64/rt-amd64, loong64/loong64, ppc64el/powerpc64le, ppc64el/powerpc64le-64k, s390x/s390x
- ?
- not established - no Makefile entry for the affected file
- M
- a module where it is built at all; some flavours do not build it
- Y
- built in where it is built at all; some flavours do not build it
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.
- Build switch
- CONFIG_POWER_SEQUENCING
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
- 2026-07-24 (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
- 0.12%, higher than 1.5% of all CVEssource
- CISA KEV
- not listedthe KEV catalogue
- Debian urgency
- unimportantsource
- Subsystem
- drivers/power
Upstream fixes
The versions the CNA records as introducing and fixing this, and the commit for each. source
| Introduced | Fixed in | Commit |
|---|---|---|
| 6.11 | 6.12.95 | ba0b9f04c7a5 |
| 6.11 | 6.18.38 | e91df6d27344 |
| 6.11 | 7.1.3 | 73569a44fca2 |
| 6.11 | 7.2 | 257595adf9da |
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 vulnerability is reached by locally opening and reading the pwrseq debugfs file, which flows through seq_read_iter() into pwrseq_debugfs_seq_next(). No network, radio, or remotely reachable protocol invokes this path.
- AC:LAttack complexity, low
- On an affected system with at least two registered power-sequencer devices, a sufficiently large read deterministically invokes next() followed by show() on the prematurely unreferenced device. No race or victim-controlled timing is required.
- PR:LPrivileges required, low
- The pwrseq node is created as 0444 with no capability check, so an ordinary local user can trigger it when debugfs is exposed through its supported mode or ownership options. Although debugfs defaults to a root-only 0700 root and cannot be mounted from an unprivileged user namespace, unprivileged-readable diagnostic deployments are reasonable.
- UI:NUser interaction, none
- The attacker triggers the vulnerability directly by reading the debugfs file; no action by another user is necessary.
- S:UScope, unchanged
- Exploitation affects the kernel and resources governed by the same operating-system security authority. The path does not cross a VM, IOMMU, or comparable isolation boundary.
- C:HConfidentiality impact, high
- The premature device-reference release creates a use-after-free involving a heap-allocated pwrseq_device whose device, name, target, unit, and list pointers are subsequently dereferenced. Heap reclamation can therefore provide a powerful kernel-memory disclosure primitive.
- I:HIntegrity impact, high
- Reclaiming the freed object with attacker-influenced data can make subsequent device, klist, list, and reference-count operations act on forged pointers. This is defensibly exploitable for arbitrary kernel-memory corruption and control-flow hijacking.
- A:HAvailability impact, high
- The stale pointer can cause invalid device or list traversal, refcount corruption, an oops, or a kernel panic. The attacker can repeatedly invoke the vulnerable read path.