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CVE-2026-46274
io-wq: check that the predecessor is hashed in io_wq_remove_pending()
Published 2026-06-08 (4 months ago) by the Linux kernel CNA. Subsystem io_uring. Debian urgency: not yet assigned.
What to do, per Debian release
Debian's own status for CVE-2026-46274 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 | vulnerable | 6.1.190-1 | No fix published anywhere yet, neither in Debian nor upstream for the series bookworm tracks. Watch the Debian tracker page for this CVE. Advisories for bookworm have historically landed a median of 23 days after publication. |
| Debian 13trixie | fixedDSA-6355-1 · 2026-06-21 · text | 6.12.94-1 | Update the kernel and reboot. DSA-6355-1 shipped the fix on 2026-06-21, 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
io_wq_remove_pending() needs to fix up wq->hash_tail[] if the cancelled work was the tail of its hash bucket. When doing this, it checks whether the preceding entry in acct->work_list has the same hash value, but never checks that the predecessor is hashed at all. io_get_work_hash() is simply atomic_read(&work->flags) >> IO_WQ_HASH_SHIFT, and the hash bits are never set for non-hashed work, so it returns 0. Thus, when a hashed bucket-0 work is cancelled while a non-hashed work is its list predecessor, the check spuriously passes and a pointer to the non-hashed io_kiocb is stored in wq->hash_tail[0]. Because non-hashed work is dequeued via the fast path in io_get_next_work(), which never touches hash_tail[], the stale pointer is never cleared. Therefore, after the non-hashed io_kiocb completes and is freed back to req_cachep, wq->hash_tail[0] is a dangling pointer. The io_wq is per-task (tctx->io_wq) and survives ring open/close, so the dangling pointer persists for the lifetime of the task; the next hashed bucket-0 enqueue dereferences it in io_wq_insert_work() and wq_list_add_after() writes through freed memory. Add the missing io_wq_is_hashed() check so a non-hashed predecessor never inherits a hash_tail[] slot.
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-wq.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_WQ /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_WQ
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
- 2026-06-08 (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
- 0.14%, higher than 2.9% of all CVEssource
- CISA KEV
- not listedthe KEV catalogue
- Debian urgency
- not yet assignedsource
- 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 |
|---|---|---|
| 5.9 | 6.6.141 | d6bda9df0c0a |
| 5.9 | 6.12.91 | 5a20ebf0c81b |
| 5.9 | 6.18.33 | 252c5051dba9 |
| 5.9 | 7.0.10 | d376c131af7c |
| 5.9 | 7.1 | d6a2d7b04b5a |
| 5.8.6 | 0 | 0 |
Debian advisories
| Advisory | Date | Shipped to | Debian |
|---|---|---|---|
| DSA-6355-1 | 2026-06-21 | trixie 6.12.94-1 | 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 bug is reached only through io_uring syscalls (io_uring_setup/io_uring_enter) that enqueue and cancel async io-wq work; there is no network, adjacent-radio, or physical-device entry path to io_wq_remove_pending().
- AC:LAttack complexity, low
- An attacker fully controls the trigger sequence—queue a non-hashed async request, queue a hashed bucket-0 request behind it, cancel the hashed pending work, let the non-hashed work complete, then enqueue another hashed bucket-0 request—with no dependence on uncontrollable timing or rare kernel configuration.
- PR:LPrivileges required, low
- Any unprivileged local user who can invoke io_uring (default when kernel.io_uring_disabled=0) can drive the cancel/enqueue sequence; no real-root or special capability beyond normal local process access is required.
- UI:NUser interaction, none
- Exploitation requires only the attacker's own io_uring submissions and cancellations; no victim user action such as opening files or mounting filesystems is needed beyond what the attacker initiates.
- S:UScope, unchanged
- The flaw corrupts kernel heap memory within the same kernel security domain to escalate from local user to kernel privileges; it does not inherently cross a VM/host or IOMMU boundary on its own.
- C:HConfidentiality impact, high
- The stale hash_tail pointer is a use-after-free of a freed io_kiocb slab object; subsequent dereferences in io_wq_insert_work() read freed memory and UAF heap corruption is routinely weaponizable for arbitrary kernel memory disclosure.
- I:HIntegrity impact, high
- io_wq_insert_work() calls wq_list_add_after(), which writes attacker-influenced list pointers through the freed io_kiocb's list.next field, providing a controlled heap write primitive suitable for further memory corruption or code execution.
- A:HAvailability impact, high
- Dereferencing and writing through the dangling hash_tail pointer can cause kernel oops/panic from invalid slab access, and successful heap corruption can crash or hang the system even before full exploitation.