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CVE-2026-80709
s390/zcrypt: Fix wrong domain value verification with EP11 CPRBs
Published 2026-08-28 (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-2026-80709 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 | fixed | 6.12.105-1 | Update the kernel and reboot. Fixed 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
There is a wrong upper limit check for the domain value when an EP11 CPRB is processed for sending to a crypto card. This check is only active on custom device nodes but may lead to access heap memory behind perms->adm when an administrative CPRB is sent. Add correct limit (AP_DOMAINS = 256) checking to fix this.
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_api.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
- 2026-08-28 (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
- 0.18%, higher than 6.7% 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 |
|---|---|---|
| 5.18 | 6.1.183 | 4589f742718d |
| 5.18 | 6.6.151 | b505dcc8307d |
| 5.18 | 6.12.103 | 13e53d6ae1c3 |
| 5.18 | 6.18.44 | 672b12940e3f |
| 5.18 | 7.1.8 | 1223477ca88e |
| 5.18 | 7.2 | 983279d7f86a |
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 |
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
- Reached only via ZSENDEP11CPRB ioctl on an s390 zcrypt custom zcdn character device (zcrypt_unlocked_ioctl -> zsendep11cprb_ioctl -> _zcrypt_send_ep11_cprb); no network, radio, or physical-bus entry path exists.
- AC:LAttack complexity, low
- A local attacker with a permitted zcdn fd fully controls ep11_urb/CPRB target_id and the admin flag; domain values 256-65534 reliably trigger the flawed test_bit_inv() past perms->adm without races or conditions outside attacker control.
- PR:LPrivileges required, low
- Exploitation requires local access to a custom zcdn node with ZSENDEP11CPRB enabled in ioctlmask; IBM Z/LinuxONE deployments routinely delegate such restricted crypto device access to non-root service accounts, not init-namespace root alone.
- UI:NUser interaction, none
- The attacker triggers the flaw by issuing ZSENDEP11CPRB with a crafted administrative EP11 CPRB from their own process; no separate victim action such as mounting a filesystem or opening a file is required.
- S:UScope, unchanged
- Impact is kernel heap out-of-bounds read and bypass of per-device admin-domain filtering within the host kernel address space; it does not cross a VM, IOMMU, or other changed security-authority boundary.
- C:HConfidentiality impact, high
- Using domain 256-65534 with an admin CPRB makes test_bit_inv() index beyond the 256-bit perms->adm bitmap, reading adjacent kmalloc heap memory behind the zcdn_device allocation.
- I:HIntegrity impact, high
- If the out-of-bounds read observes a set bit, the admask admin-domain check passes and unauthorized EP11 administrative CPRBs can reach crypto control domains outside the device's intended permissions.
- A:HAvailability impact, high
- Large crafted domain values make test_bit_inv() read far beyond the zcdn_device kmalloc object, which can access unmapped memory and provoke a kernel oops or panic during the ioctl path.