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CVE-2026-63824
KEYS: fix overflow in keyctl_pkey_params_get_2()
Published 2026-07-19 (3 months ago) by the Linux kernel CNA. Subsystem security/keys. Debian urgency: not yet assigned.
What to do, per Debian release
Debian's own status for CVE-2026-63824 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
The length for the internal output buffer is calculated incorrectly, which can result overflow when a too small buffer is provided. Fix the bug by allocating internal output with the size of the maximum length of the cryptographic primitive instead of caller provided size.
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.
security/keys/keyctl_pkey.c
- What this is
- KEYS/KEYRINGSMAINTAINERS section matched on security/keys/ · keyrings@vger.kernel.org · Maintained
Check it on the machine
grep -wE 'CONFIG_ASYMMETRIC_KEY_TYPE|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 switches
- CONFIG_ASYMMETRIC_KEY_TYPE, CONFIG_KEYS
- 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
- 2026-07-19 (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
- 0.13%, higher than 2.3% of all CVEssource
- CISA KEV
- not listedthe KEV catalogue
- Debian urgency
- not yet assignedsource
- Subsystem
- security/keys
Upstream fixes
The versions the CNA records as introducing and fixing this, and the commit for each. source
| Introduced | Fixed in | Commit |
|---|---|---|
| 4.20 | 5.10.260 | 622ec2dcd59f |
| 4.20 | 5.15.211 | b1e247338bc7 |
| 4.20 | 6.1.177 | 0f3058d7d26f |
| 4.20 | 6.6.144 | 5966e4e2ba21 |
| 4.20 | 6.12.95 | 5165f1cc727f |
| 4.20 | 6.18.38 | b11c1fa32667 |
| 4.20 | 7.1.3 | 670fc6a311ed |
| 4.20 | 7.2 | cb481e59ea6c |
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 vulnerability is reachable only through the keyctl(2) syscall (KEYCTL_PKEY_ENCRYPT, KEYCTL_PKEY_DECRYPT, or KEYCTL_PKEY_SIGN); there is no network, adjacent, or physical attack path to the affected code.
- AC:LAttack complexity, low
- An attacker fully controls the undersized out_len parameter and can reliably trigger the bug on demand with no races or victim-dependent state; CONFIG_ASYMMETRIC_KEY_TYPE is commonly enabled on server and desktop kernels.
- PR:LPrivileges required, low
- Exploitation requires KEY_NEED_SEARCH on an asymmetric key, which any unprivileged local user can satisfy by loading their own RSA/EC key into a session keyring; no real root or init-namespace capabilities are needed.
- UI:NUser interaction, none
- Exploitation requires only attacker-initiated keyctl calls and does not depend on any victim user action such as opening a file or mounting a filesystem.
- S:UScope, unchanged
- Impact is confined to kernel heap memory corruption and privilege escalation within the same kernel security boundary; this is not a VM escape, sandbox escape, or cross-authority boundary violation.
- C:HConfidentiality impact, high
- When out_len is smaller than the cryptographic output (including out_len=0 where kmalloc(0) yields ZERO_SIZE_PTR), asym_eds_op returns the full primitive output size and copy_to_user reads far beyond the allocated buffer, leaking adjacent kernel heap contents to userspace.
- I:HIntegrity impact, high
- The undersized kmalloc buffer is passed directly as the crypto output target; asymmetric operations can write up to the primitive maximum (hundreds of bytes for RSA-4096) past the allocation, enabling heap corruption and potential control-flow hijacking.
- A:HAvailability impact, high
- Heap out-of-bounds read/write against kmalloc objects or writes through ZERO_SIZE_PTR can cause kernel oops, panic, or KASAN-detected corruption, satisfying high availability impact.