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CVE-2026-93262
md/raid5-ppl: fix use-after-free in ppl_do_flush()
Published 2026-09-24 (24 days ago) by the Linux kernel CNA. Subsystem drivers/md. Debian urgency: not yet assigned.
What to do, per Debian release
Debian's own status for CVE-2026-93262 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 | fixedDLA-4841-1 · 2026-10-17 · text | 6.1.190-1 | Update the kernel and reboot. DLA-4841-1 shipped the fix on 2026-10-17, in 6.1.190-1. A running kernel keeps the old code until the machine restarts. |
| Debian 13trixie | fixedDSA-6528-1 · 2026-09-29 · text | 6.12.111-1 | Update the kernel and reboot. DSA-6528-1 shipped the fix on 2026-09-29, in 6.12.111-1. A running kernel keeps the old code until the machine restarts. |
| Debian 14forky | fixed | 7.2.6-1 | Update the kernel and reboot. Fixed in 7.2.6-1. A running kernel keeps the old code until the machine restarts. |
| Debian unstablesid | fixed | 7.2.6-1 | Update the kernel and reboot. Fixed in 7.2.6-1. A running kernel keeps the old code until the machine restarts. |
| Debian 12bookworm · linux-6.12 | fixedDLA-4817-1 · 2026-10-04 · text | 6.12.111-1~deb12u1 | Update the kernel and reboot. DLA-4817-1 shipped the fix on 2026-10-04, in 6.12.111-1~deb12u1. A running kernel keeps the old code until the machine restarts. |
The vulnerability
What the bug is
The loop in ppl_do_flush() continues iterating after calling ppl_io_unit_finished(), touching io->pending_flushes and leading to a use-after-free. Add a break statement to stop the loop once io is freed.
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/md/raid5-ppl.c
- What this is
- SOFTWARE RAID (Multiple Disks) SUPPORTMAINTAINERS section matched on drivers/md/raid* · linux-raid@vger.kernel.org · Supported
- Kernel module
- raid456
Check it on the machine
grep -wE 'CONFIG_MD|CONFIG_MD_RAID456' /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 raid456Prints 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 as a loadable module. Every release below compiles it as a module on every flavour, so whether the code is in the running kernel depends on whether that module is loaded.
- bookworm, trixie, forky, sid, bookworm · linux-6.12m
- m
- a loadable module on every flavour - check lsmod, can be blacklisted
- Build switches
- CONFIG_MD, CONFIG_MD_RAID456
- 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
- 2026-09-24 (24 days 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
- 0.15%, higher than 3.7% of all CVEssource
- CISA KEV
- not listedthe KEV catalogue
- Debian urgency
- not yet assignedsource
- Subsystem
- drivers/md
Upstream fixes
The versions the CNA records as introducing and fixing this, and the commit for each. source
| Introduced | Fixed in | Commit |
|---|---|---|
| 4.16 | 5.10.270 | cf01f9413565 |
| 4.16 | 5.15.221 | e7505842f132 |
| 4.16 | 6.1.188 | b5123bf667ac |
| 4.16 | 6.6.157 | e77c80670f2c |
| 4.16 | 6.12.110 | 8914c3d40870 |
| 4.16 | 6.18.52 | 455b56209f96 |
| 4.16 | 7.2.6 | fcf21df7d3c5 |
| 4.16 | 7.3 | 371f7a1b392e |
Debian advisories
| Advisory | Date | Shipped to | Debian |
|---|---|---|---|
| DLA-4841-1 | 2026-10-17 | bookworm 6.1.190-1 | tracker |
| DLA-4817-1 | 2026-10-04 | bookworm 6.12.111-1~deb12u1 | tracker |
| DSA-6528-1 | 2026-09-29 | trixie 6.12.111-1 | tracker |
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 patched ppl_do_flush() runs from ppl_stripe_write_finished() after RAID5 stripe data+parity I/O completes. Those writes enter via md_submit_bio() -> raid5_make_request() from local write(2) to a filesystem or /dev/md*; ppl_submit_iounit() only sets disk_flush_bitmap from local stripe R5_Wantwrite/wb_cache_on state, not from a network protocol message.
- AC:LAttack complexity, low
- Writes the attacker issues are logged by ppl_write_stripe()/ppl_log_stripe() and ppl_submit_iounit() sets disk_flush_bitmap for child_logs[i].wb_cache_on members. When pending_stripes hits 0, ppl_stripe_write_finished() calls ppl_do_flush(); the remainder loop's missing break after ppl_io_unit_finished() is a logic bug on that path, not a second-actor race or a disk-fault precondition.
- PR:LPrivileges required, low
- md_submit_bio() and raid5_make_request() have no capability check; md_ioctl()'s capable(CAP_SYS_ADMIN) applies only to array-management ioctls, not I/O. An unprivileged user who can write a filesystem on the RAID5+PPL array (or /dev/md* with disk-group write access) reaches ppl_do_flush() without init-namespace root.
- UI:NUser interaction, none
- The attacker triggers ppl_do_flush() through their own writes: raid5 handle_stripe()/handle_stripe_clean_event() calls ppl_stripe_write_finished() on I/O they submitted. No victim action such as mounting an image or plugging a device is required.
- S:UScope, unchanged
- ppl_io_unit_finished() mempool_free()s the ppl_io_unit from ppl_conf->io_pool in the host md/raid5 kernel. The later dangling atomic_dec_and_test(&io->pending_flushes) in ppl_do_flush() stays in that kernel's authority and does not cross a VM, IOMMU, or sandbox boundary.
- C:HConfidentiality impact, high
- ppl_io_unit_finished() returns the ppl_io_unit to io_pool via mempool_free(); ppl_do_flush()'s remainder loop then does atomic_dec_and_test(&io->pending_flushes) on that freed kmem_cache object. A UAF of the recycled io_unit header is a kernel read primitive against adjacent/reconstituted pool memory.
- I:HIntegrity impact, high
- The same dangling io is a writeable ppl_io_unit: atomic_dec_and_test() mutates pending_flushes on a recycled object, and another true dec_and_test would call ppl_io_unit_finished() again (list_del/mempool_free of a live unit). That is a kernel write/double-free primitive on the PPL io_unit cache.
- A:HAvailability impact, high
- Use-after-free of the mempool ppl_io_unit in ppl_do_flush() after ppl_io_unit_finished() can oops on the stale pending_flushes access or corrupt list_del() pointers in a second finish, panicking the host.