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CVE-2026-68451
s390/zcrypt: Validate length for CCA ECC private key requests
Published 2026-08-13 (2 months ago) by the Linux kernel CNA. Subsystem drivers/s390. Debian urgency: not yet assigned.
What to do, per Debian release
Debian's own status for CVE-2026-68451 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 | fixedDLA-4777-1 · 2026-09-08 · text | 6.1.187-1 | Update the kernel and reboot. DLA-4777-1 shipped the fix on 2026-09-08, in 6.1.187-1. A running kernel keeps the old code until the machine restarts. |
| Debian 13trixie | fixedDSA-6466-1 · 2026-08-25 · text | 6.12.105-1 | Update the kernel and reboot. DSA-6466-1 shipped the fix on 2026-08-25, in 6.12.105-1. A running kernel keeps the old code until the machine restarts. |
| Debian 14forky | fixed | 7.1.8-1 | Update the kernel and reboot. Fixed in 7.1.8-1. A running kernel keeps the old code until the machine restarts. |
| Debian unstablesid | fixed | 7.1.8-1 | Update the kernel and reboot. Fixed in 7.1.8-1. A running kernel keeps the old code until the machine restarts. |
| Debian 12bookworm · linux-6.12 | fixedDLA-4788-1 · 2026-09-19 · text | 6.12.107-1~deb12u1 | Update the kernel and reboot. DLA-4788-1 shipped the fix on 2026-09-19, in 6.12.107-1~deb12u1. A running kernel keeps the old code until the machine restarts. |
The vulnerability
What the bug is
cca_ecc2protkey() derives the copy length for the CPRB parameter block directly from the length field in the key token. Reject the request early if the token length exceeds the available space in the parameter block.
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.
drivers/s390/crypto/zcrypt_ccamisc.c
- What this is
- S390 ZCRYPT AND PKEY DRIVER AND AP BUSMAINTAINERS section matched on drivers/s390/crypto/ · linux-s390@vger.kernel.org · Supported
- Kernel module
- zcrypt
Check it on the machine
grep -wE 'CONFIG_S390|CONFIG_ZCRYPT' /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 zcryptPrints 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 does not build this code in 2 releases. It does build it in 3 releases, so the answer depends on which release the machine runs.
- bookwormn
- trixieMnot built on amd64/amd64, amd64/cloud-amd64, amd64/rt/amd64, arm64/arm64, arm64/arm64-16k, arm64/cloud-arm64, arm64/rt/arm64, armel/rpi, armhf/armmp, armhf/armmp-lpae, armhf/rt/armmp, ppc64el/powerpc64le, ppc64el/powerpc64le-64k, riscv64/riscv64
- forky, sidMnot built on amd64/amd64, amd64/cloud-amd64, amd64/rt-amd64, arm64/arm64, arm64/arm64-16k, arm64/cloud-arm64, arm64/rt-arm64, armhf/armmp, armhf/armmp-lpae, loong64/loong64, ppc64el/powerpc64le, ppc64el/powerpc64le-64k, riscv64/riscv64
- bookworm · linux-6.12n
- n
- not enabled on any flavour - this release does not build the code
- M
- a module where it is built at all; some flavours do not build it
- Build switches
- CONFIG_S390, CONFIG_ZCRYPT
- 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
- 2026-08-13 (2 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 2.5% of all CVEssource
- CISA KEV
- not listedthe KEV catalogue
- Debian urgency
- not yet assignedsource
- Subsystem
- drivers/s390
Upstream fixes
The versions the CNA records as introducing and fixing this, and the commit for each. source
| Introduced | Fixed in | Commit |
|---|---|---|
| 5.10 | 5.10.265 | 7dc306ff7c4d |
| 5.10 | 5.15.216 | 447a37a6bef1 |
| 5.10 | 6.1.183 | f0831f13c42c |
| 5.10 | 6.6.151 | dd25bd9b0f36 |
| 5.10 | 6.12.103 | ecc3b8691c19 |
| 5.10 | 6.18.44 | 013a4484f061 |
| 5.10 | 7.1.8 | 8fa3e9435a13 |
| 5.10 | 7.2 | a9ae0f6dd45c |
Debian advisories
| Advisory | Date | Shipped to | Debian |
|---|---|---|---|
| DLA-4788-1 | 2026-09-19 | bookworm 6.12.107-1~deb12u1 | tracker |
| DLA-4777-1 | 2026-09-08 | bookworm 6.1.187-1 | tracker |
| DSA-6466-1 | 2026-08-25 | trixie 6.12.105-1 | 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 through the `/dev/pkey` misc device via the PKEY_KBLOB2PROTK/PROTK2/PROTK3 ioctls, requiring local access to the s390 system; there is no remote or network-facing path into cca_ecc2protkey().
- AC:LAttack complexity, low
- The attacker fully controls both the overflow length and the overflowing bytes by crafting the ECC key token's `len` field and blob contents, and the memcpy executes deterministically on every call with no race, timing, or layout precondition.
- PR:LPrivileges required, low
- The pkey misc device is registered with mode 0666 and pkey_unlocked_ioctl performs no capability check, so any unprivileged local user (or a container/sandbox process with the node visible) can issue the ioctl.
- UI:NUser interaction, none
- The attacker triggers the overflow entirely from its own ioctl call; no action by another user or administrator is needed.
- S:UScope, unchanged
- The heap corruption occurs in kernel memory within the same security authority; no VM, IOMMU, or other trust boundary is crossed by the overflow itself.
- C:HConfidentiality impact, high
- The controlled slab overflow can overwrite adjacent kernel objects (pointers, lengths, credentials) with attacker-chosen data, which is readily leveraged into arbitrary kernel memory disclosure, including protected/secure key material handled by this subsystem.
- I:HIntegrity impact, high
- memcpy() writes up to ~7 KB of fully attacker-controlled data past a kmalloc'd CPRB buffer, giving a classic controlled heap out-of-bounds write usable for corrupting neighbouring slab objects and achieving privilege escalation or control-flow hijack.
- A:HAvailability impact, high
- Even without reliable exploitation, the oversized memcpy smashes the slab and neighbouring allocations, causing memory corruption, SLUB/redzone BUG detonations, oops or kernel panic, repeatedly triggerable by an unprivileged user.