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CVE-2026-80924
crypto: krb5 - use kfree_sensitive() for derived key buffers
Published 2026-09-09 (39 days ago) by the Linux kernel CNA. Subsystem crypto/krb5. Debian urgency: unimportant.
What to do, per Debian release
Debian's own status for CVE-2026-80924 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 | not affected | 6.12.113-1 | Nothing to do. trixie never shipped the vulnerable code. |
| Debian 14forky | fixed | 7.1.13-1 | Update the kernel and reboot. Fixed in 7.1.13-1. A running kernel keeps the old code until the machine restarts. |
| Debian unstablesid | fixed | 7.1.13-1 | Update the kernel and reboot. Fixed in 7.1.13-1. A running kernel keeps the old code until the machine restarts. |
The vulnerability
What the bug is
crypto_krb5_prepare_encryption() and crypto_krb5_prepare_checksum() free the buffer holding the freshly derived keys with plain kfree(), leaving the key material behind in the freed slab object.
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.
crypto/krb5/krb5_api.c
- What this is
- CRYPTO APIMAINTAINERS section matched on crypto/ · linux-crypto@vger.kernel.org · Maintained
- Kernel module
- krb5
Check it on the machine
grep -w CONFIG_CRYPTO_KRB5 /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 krb5Prints 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 with an answer 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. The build rule could not be established for 2 releases, so nothing is claimed about those.
- bookworm, trixie?
- forky, sidm
- ?
- not established - no Makefile entry for the affected file
- m
- a loadable module on every flavour - check lsmod, can be blacklisted
Where a release above reads "not established", no build rule for the affected file was found in that release's kernel tree. That is a gap in this lookup, not a finding that the code is absent.
- Build switch
- CONFIG_CRYPTO_KRB5
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
- 2026-09-09 (39 days ago)source
- CVSS
- 7.5 high
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:Nsource recompute it - Attack vector
- network (AV:N)source
- EPSS
- 0.32%, higher than 23.7% of all CVEssource
- CISA KEV
- not listedthe KEV catalogue
- Debian urgency
- unimportantsource
- Subsystem
- crypto/krb5
Upstream fixes
The versions the CNA records as introducing and fixing this, and the commit for each. source
| Introduced | Fixed in | Commit |
|---|---|---|
| 6.15 | 6.18.49 | 731a5b6fb4c1 |
| 6.15 | 7.1.13 | 91b96dc9cc25 |
| 6.15 | 7.2.3 | a1bf79365794 |
| 6.15 | 7.3 | f7d53dd3f267 |
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:NAttack vector, network
- crypto_krb5_prepare_encryption() and crypto_krb5_prepare_checksum() run from nfsd RPCSEC_GSS on TCP/2049, from in-kernel RxGK handshake processing of remote RESPONSE packets (rxgk_extract_token/rxgk_set_up_token_cipher), and from Ceph/AFS network-filesystem security, so a remote peer can cause derived Kerberos keys to be left in freed slab.
- AC:LAttack complexity, low
- Each prepare path derives Ke/Ki/Kc into a kmalloc buffer then frees it with plain kfree(); the leftover is deterministic on every GSS/RxGK/Ceph context setup, with no race or attacker-uncontrollable memory layout required to leave the keys in the slab.
- PR:NPrivileges required, none
- RxGK token-cipher setup runs while decrypting the authentication token, before the token or authenticator is verified, and nfsd RPCSEC_GSS INIT is the authentication handshake; a network peer needs no local Linux account or capability to drive these pre-auth paths.
- UI:NUser interaction, none
- A Kerberos NFS server or RxRPC/AFS endpoint automatically processes incoming GSS/RxGK handshake packets; no victim mount, click, or other interactive action is required at exploit time.
- S:UScope, unchanged
- Leftover keys remain in host-kernel slab; this is ordinary kernel information disclosure within the same security authority, not a VM escape, IOMMU bypass, or sandbox breakout.
- C:HConfidentiality impact, high
- The freed buffers hold complete derived Kerberos encryption and integrity keys (Ke/Ki/Kc, up to 32-byte AES-256 material). Recovering them from reused slab yields full session-key disclosure for NFS, AFS, Ceph, or RxGK traffic.
- I:NIntegrity impact, none
- The bug only fails to wipe key material before kfree(); it does not corrupt kernel memory, provide a write primitive, or hijack control flow.
- A:NAvailability impact, none
- Replacing kfree() with kfree_sensitive() does not affect control flow; the plain kfree() path does not oops, deadlock, leak allocator objects, or otherwise impact availability.