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CVE-2026-81007
ipmi: ipmb: validate write message length
Published 2026-09-11 (37 days ago) by the Linux kernel CNA. Subsystem drivers/char. Debian urgency: not yet assigned.
Debian does not build this code. The per-release build detail is under "Where it lives" below.
What to do, per Debian release
Debian's own status for CVE-2026-81007 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
ipmb_write() read message fields before validating the length byte. A zero or short write can read uninitialized stack bytes. A length smaller than the SMBus header underflows the block write length. Require a non-empty buffer and the minimum IPMB request length. Also require the length byte plus payload before parsing the message.
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/char/ipmi/ipmb_dev_int.c
- What this is
- IPMI SUBSYSTEMMAINTAINERS section matched on drivers/char/ipmi/ · openipmi-developer@lists.sourceforge.net · Supported
- Kernel module
- none to look for. The file would have gone into ipmb_dev_int, and Debian does not compile it into that module, so finding ipmb_dev_int in lsmod would say nothing about this CVE.
Check it on the machine
grep -w CONFIG_IPMB_DEVICE_INTERFACE /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 does not build this code. In 5 releases below, every kernel flavour Debian publishes has the switch off, so the vulnerable file is compiled into no kernel binary Debian ships.
- bookworm, trixie, forky, sid, bookworm · linux-6.12n
- n
- not enabled on any flavour - this release does not build the code
- Build switch
- CONFIG_IPMB_DEVICE_INTERFACE
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
- 7.1 high
CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:N/A:Hsource recompute it - Attack vector
- local (AV:L)source
- EPSS
- 0.13%, higher than 2.0% of all CVEssource
- CISA KEV
- not listedthe KEV catalogue
- Debian urgency
- not yet assignedsource
- Subsystem
- drivers/char
Upstream fixes
The versions the CNA records as introducing and fixing this, and the commit for each. source
| Introduced | Fixed in | Commit |
|---|---|---|
| 5.3 | 5.10.270 | 8990c7f6bfc1 |
| 5.3 | 5.15.221 | 94f8d20153e3 |
| 5.3 | 6.1.188 | e527cd4e8006 |
| 5.3 | 6.6.157 | 7d66d54b974c |
| 5.3 | 6.12.109 | 60939bcda6f3 |
| 5.3 | 6.18.50 | 5719431ca2b5 |
| 5.3 | 7.2.4 | a84c6e3d188f |
| 5.3 | 7.3 | 53637506884d |
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
- ipmb_write() is the miscdevice write handler for /dev/ipmb-N and is reached only via a local write(2) on that character device. The I2C slave callback queues inbound IPMB requests for read() and does not enter this path.
- AC:LAttack complexity, low
- A single write of count 0, or a 1-byte write with length field 0, bypasses the old count<msg[0] check and underflows the I2C/SMBus length. The attacker fully controls the buffer; no race or uninfluenced memory layout is required.
- PR:LPrivileges required, low
- Neither ipmb_write() nor misc_open() performs a capability check; access is only DAC on /dev/ipmb-N. BMC and satellite-MC deployments (OpenBMC ipmbbridge, OpenIPMI) commonly grant this node to a non-root management or service account rather than requiring init-namespace root.
- UI:NUser interaction, none
- The attacker triggers the bug entirely with their own write(2) to an already-present /dev/ipmb-N node. No other user must open a file, mount a filesystem, or otherwise interact.
- S:UScope, unchanged
- The out-of-bounds stack read and resulting kernel oops remain inside the same host kernel security authority. IPMB/I2C is an in-chassis management bus, not a VM, IOMMU, or sandbox boundary crossing.
- C:HConfidentiality impact, high
- On i2c-protocol devices (usual OpenBMC/Aspeed DT), a zero length byte promotes to i2c_msg.len 65535, so i2c_transfer/DMA helpers read tens of kilobytes past the 240-byte stack buffer, disclosing kernel stack contents onto the IPMB bus.
- I:NIntegrity impact, none
- The defect is an out-of-bounds read of a stack buffer used as an I2C write payload. It does not write kernel memory, corrupt heap objects, or yield a control-flow or arbitrary-write primitive.
- A:HAvailability impact, high
- The 65535-byte stack over-read walks off the kernel stack. Aspeed I2C (typical OpenBMC IPMB adapter) has no max_write_len quirk, so the transfer or memcpy hits the VMAP_STACK guard page and oopses the kernel.