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CVE-2026-98858
io_uring: fix task_work add use-after-free with SQPOLL
Published 2026-10-18 (today) by the Linux kernel CNA. Subsystem io_uring. Debian urgency: unimportant.
What to do, per Debian release
Debian's own status for CVE-2026-98858 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 | 6.12.113-1 | Update the kernel and reboot. Fixed in 6.12.113-1. A running kernel keeps the old code until the machine restarts. |
| Debian 14forky | fixed | 7.2.10-1 | Update the kernel and reboot. Fixed in 7.2.10-1. A running kernel keeps the old code until the machine restarts. |
| Debian unstablesid | fixed | 7.2.10-1 | Update the kernel and reboot. Fixed in 7.2.10-1. A running kernel keeps the old code until the machine restarts. |
The vulnerability
What the bug is
For SQPOLL, the sqpoll thread runs task_work off its own list and doesn't need to be told about it, so it can pop and complete a request as soon as mpscq_push() has published it. If that was the last request holding the ring alive, io_ring_exit_work() then frees the ctx, stops the thread, and with it the tctx, while io_req_normal_work_add() is still looking at both after the push: BUG: KASAN: slab-use-after-free in io_req_normal_work_add+0x439/0x510 Read of size 4 at addr ff11000000ca0000 by task repro/55 (...) BUG: KASAN: slab-use-after-free in queue_work_on+0x25/0x70 Write of size 8 at addr ff11000000c3bd00 by task repro/55 Hold an RCU read lock across the add, like io_req_local_work_add() already does, and have io_ring_exit_work() wait for a grace period for SQPOLL rings as well before freeing the ctx.
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.
io_uring/io_uring.c
io_uring/tw.c
- What this is
- IO_URINGMAINTAINERS section matched on io_uring/ · io-uring@vger.kernel.org · Maintained
Check it on the machine
grep -w CONFIG_IO_URING /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_IO_URING
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
- 2026-10-18 (today)source
- CVSS
- no vector published, unrated
- Attack vector
- not published
- EPSS
- not scored
- CISA KEV
- not listedthe KEV catalogue
- Debian urgency
- unimportantsource
- Subsystem
- io_uring
Upstream fixes
The versions the CNA records as introducing and fixing this, and the commit for each. source
| Introduced | Fixed in | Commit |
|---|---|---|
| 6.9 | 6.12.113 | 42b3332efacf |
| 6.9 | 6.18.56 | 891bd8335a0d |
| 6.9 | 7.2.10 | 395b25968fe8 |
| 6.9 | 7.3 | a92193c91e88 |
Why the CNA scored it this way
The kernel CNA published no CVSS vector and no reasoning for CVE-2026-98858, which is why it is shown as unrated rather than given an invented score. 6,405 of the 20,413 CVEs here carry reasoning; this is not one of them.