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CVE-2026-63823
keys: Pin request_key_auth payload in instantiate paths
Published 2026-07-19 (3 months ago) by the Linux kernel CNA. Subsystem include/keys. Debian urgency: not yet assigned.
What to do, per Debian release
Debian's own status for CVE-2026-63823 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 | fixed | 6.1.177-1 | Update the kernel and reboot. Fixed in 6.1.177-1. A running kernel keeps the old code until the machine restarts. |
| 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
A: request_key() B: KEYCTL_INSTANTIATE_IOV ================ ========================= create auth key store rka in auth key wait for helper get auth key load rka from auth key copy user payload sleep on #PF helper completed detach and free rka destroy auth key wake up use rka->target_key **USE-AFTER-FREE** Give request_key_auth payloads a refcount. Take a payload reference while authkey->sem stabilizes the payload and revocation state. Hold that reference across the instantiate and reject paths. Drop the auth key owning reference from revoke and destroy. [jarkko: Replaced the first two paragraphs of text with an actual concurrency scenario.]
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.
include/keys/request_key_auth-type.h
security/keys/internal.h
security/keys/keyctl.c
security/keys/request_key_auth.c
- What this is
- KEYS/KEYRINGSMAINTAINERS section matched on include/keys/ · keyrings@vger.kernel.org · Maintained
Check it on the machine
grep -w CONFIG_KEYS /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_KEYS
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
- 2026-07-19 (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 1.9% of all CVEssource
- CISA KEV
- not listedthe KEV catalogue
- Debian urgency
- not yet assignedsource
- Subsystem
- include/keys
Upstream fixes
The versions the CNA records as introducing and fixing this, and the commit for each. source
| Introduced | Fixed in | Commit |
|---|---|---|
| 2.6.16 | 5.10.260 | d8274181b0f2 |
| 2.6.16 | 5.15.211 | 4982bfabce6b |
| 2.6.16 | 6.1.177 | 708709c65a18 |
| 2.6.16 | 6.6.144 | 35ab4db86774 |
| 2.6.16 | 6.12.95 | f9b68632ac93 |
| 2.6.16 | 6.18.38 | 7216ce8cb12f |
| 2.6.16 | 7.1.3 | 83c0a1cb296d |
| 2.6.16 | 7.2 | fd15b457a869 |
Debian advisories
| Advisory | Date | Shipped to | Debian |
|---|---|---|---|
| DLA-4717-1 | 2026-08-05 | bullseye 5.10.262-1 | tracker |
| DLA-4700-1 | 2026-07-26 | bullseye 6.1.177-1~deb11u1 | 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 local `request_key()` and `keyctl()` syscalls (`KEYCTL_ASSUME_AUTHORITY`, `KEYCTL_INSTANTIATE`, `KEYCTL_INSTANTIATE_IOV`, `KEYCTL_REJECT`); there is no network, adjacent-radio, or physical-device entry path.
- AC:LAttack complexity, low
- Exploitation is a race the attacker orchestrates by calling `request_key()` and concurrently driving `KEYCTL_INSTANTIATE_IOV` with a user buffer that page-faults during `copy_from_iter_full()`, while a second helper thread or completion path revokes/frees the auth payload.
- PR:LPrivileges required, low
- Any unprivileged local user can invoke `request_key()` and the affected `keyctl` instantiate/reject operations in the spawned helper context; no real-root or non-userns capability is required.
- UI:NUser interaction, none
- Exploitation does not depend on a victim performing an action beyond the attacker’s own syscall activity and helper process setup.
- S:UScope, unchanged
- Impact is kernel memory corruption and local privilege escalation within the same kernel security domain, not a VM-guest-to-host or IOMMU boundary escape.
- C:HConfidentiality impact, high
- This is a heap use-after-free of `struct request_key_auth`; after free the code dereferences `rka->target_key` and related fields, enabling attacker-controlled reuse and arbitrary kernel memory disclosure.
- I:HIntegrity impact, high
- The UAF corrupts trusted kernel pointers (`target_key`, `dest_keyring`) used in `key_instantiate_and_link()`, which can be turned into arbitrary kernel writes and local privilege escalation.
- A:HAvailability impact, high
- Use-after-free of kernel heap objects can cause kernel oops/panic during post-fault dereferences, and is independently severe even before full exploitation.