Look up another CVE · open CVE-2026-89456 in the interactive tracker
CVE-2026-89456
s390/dasd: Propagate partial completion length across ERP recovery
Published 2026-09-11 (37 days 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-2026-89456 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-4841-1 · 2026-10-17 · text | 6.1.190-1 | Update the kernel and reboot. DLA-4841-1 shipped the fix on 2026-10-17, in 6.1.190-1. A running kernel keeps the old code until the machine restarts. |
| Debian 13trixie | fixedDSA-6528-1 · 2026-09-29 · text | 6.12.111-1 | Update the kernel and reboot. DSA-6528-1 shipped the fix on 2026-09-29, in 6.12.111-1. A running kernel keeps the old code until the machine restarts. |
| Debian 14forky | fixed | 7.2.6-1 | Update the kernel and reboot. Fixed in 7.2.6-1. A running kernel keeps the old code until the machine restarts. |
| Debian unstablesid | fixed | 7.2.6-1 | Update the kernel and reboot. Fixed in 7.2.6-1. A running kernel keeps the old code until the machine restarts. |
| Debian 12bookworm · linux-6.12 | fixedDLA-4817-1 · 2026-10-04 · text | 6.12.111-1~deb12u1 | Update the kernel and reboot. DLA-4817-1 shipped the fix on 2026-10-04, in 6.12.111-1~deb12u1. A running kernel keeps the old code until the machine restarts. |
The vulnerability
What the bug is
dasd_default_erp_postaction() copies the timing and device state from the finished ERP request back to the original request but drops proc_bytes. A request that was partially completed, an ESE read of a not-yet-allocated track returns fewer bytes than requested, and then recovered through the ERP chain loses its partial-completion length. __dasd_cleanup_cqr() then sees proc_bytes == 0 and completes the whole request instead of requeueing the remainder, silently returning zeroed data for the part that was never read. Carry proc_bytes over to the original request like the other per-request state.
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/block/dasd_erp.c
- What this is
- S390 DASD DRIVERMAINTAINERS section matched on drivers/s390/block/dasd* · linux-s390@vger.kernel.org · Supported
- Kernel module
- dasd_mod
Check it on the machine
grep -wE 'CONFIG_DASD|CONFIG_S390' /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 dasd_modPrints 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_DASD, CONFIG_S390
- 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
- 2026-09-11 (37 days ago)source
- CVSS
- 7.0 high
CVSS:3.1/AV:L/AC:H/PR:L/UI:N/S:U/C:H/I:H/A:Hsource recompute it - Attack vector
- local (AV:L)source
- EPSS
- 0.15%, higher than 3.7% 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 |
|---|---|---|
| 5.6 | 5.10.270 | 9e063165d3fe |
| 5.6 | 5.15.221 | 6b0954c8a259 |
| 5.6 | 6.1.188 | d0a2f97d8c97 |
| 5.6 | 6.6.157 | f735b9710f0c |
| 5.6 | 6.12.109 | d6b8778b1b82 |
| 5.6 | 6.18.50 | ceafb262475a |
| 5.6 | 7.2.4 | 15ec03452c18 |
| 5.6 | 7.3 | 6fb5ba2e7e43 |
| 5.4.26 | 0 | 0 |
| 5.5.10 | 0 | 0 |
Debian advisories
| Advisory | Date | Shipped to | Debian |
|---|---|---|---|
| DLA-4841-1 | 2026-10-17 | bookworm 6.1.190-1 | tracker |
| DLA-4817-1 | 2026-10-04 | bookworm 6.12.111-1~deb12u1 | tracker |
| DSA-6528-1 | 2026-09-29 | trixie 6.12.111-1 | 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 flaw is in the s390 DASD block driver's ERP postaction and is reached only by local block I/O to an ESE (thin-provisioned) volume, via a DASD-backed filesystem or /dev/dasd*; no ksmbd, nfsd, or packet path parses attacker data into this code.
- AC:HAttack complexity, high
- Exploitation needs an ESE NRF partial read whose CQR is an ERP retry, so a prior hardware-reported unit check or similar recoverable error must occur; the attacker cannot inject sense data or craft CCWs, which the driver builds itself.
- PR:LPrivileges required, low
- Unprivileged local users trigger the path through ordinary read/write syscalls on files stored on a DASD-backed filesystem; dasd_open and do_dasd_request impose no capability check on that I/O path.
- UI:NUser interaction, none
- The attacker performs the I/O themselves; no second user must mount a volume, open a file, or otherwise interact.
- S:UScope, unchanged
- Incorrect request completion affects host kernel block I/O and page-cache contents on the same LPAR; it is not a KVM/vfio-ccw guest-to-host escape or an IOMMU/DMA boundary bypass.
- C:HConfidentiality impact, high
- Dropping proc_bytes completes the unread remainder as success, so page-cache pages the driver never filled — stale previously freed kernel or other tenants' memory — are marked uptodate and returned to userspace as valid file data.
- I:HIntegrity impact, high
- Tracks after the unallocated ESE hole are never fetched yet the whole request succeeds, substituting zeros or stale bytes for real disk contents that filesystems may write back, permanently corrupting co-resident file data and metadata.
- A:HAvailability impact, high
- Successful completion of filesystem, journal, or executable reads with zeros or stale data can corrupt metadata parsers and trigger ext4 errors=panic or XFS forced shutdown, taking IBM Z/LinuxONE storage nodes down.