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CVE-2026-89486
ipmi: Fix use-after-free of cmd_rcvr in _ipmi_destroy_user()
Published 2026-09-11 (37 days ago) by the Linux kernel CNA. Subsystem drivers/char. Debian urgency: unimportant.
What to do, per Debian release
Debian's own status for CVE-2026-89486 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 | 7.2.6-1 | 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. |
The vulnerability
What the bug is
Commit 9e91f8a6c868 ("ipmi:msghandler: Remove srcu for the ipmi_interfaces list") dropped the synchronize_rcu() between unlinking the command receivers from intf->cmd_rcvrs and freeing them, updating only the comment that explains why the barrier is needed. The cmd_rcvrs list is still traversed under plain RCU: find_cmd_rcvr() walks it inside rcu_read_lock(), and handle_ipmb_get_msg_cmd() borrows rcvr->user from that lookup within the same read-side section. Without the grace period, _ipmi_destroy_user() can kfree() a cmd_rcvr while a reader still holds a pointer to it, causing a use-after-free. The rework only made srcu unnecessary for the interfaces list; the cmd_rcvrs list still relies on plain RCU. Restore the synchronize_rcu() before freeing the receivers.
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/ipmi_msghandler.c
- What this is
- IPMI SUBSYSTEMMAINTAINERS section matched on drivers/char/ipmi/ · openipmi-developer@lists.sourceforge.net · Supported
- Kernel module
- ipmi_msghandler
Check it on the machine
grep -w CONFIG_IPMI_HANDLER /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 ipmi_msghandlerPrints 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, but not on every flavour. At least one release below builds the code on some of its kernel flavours and not on others, so the answer depends on the architecture and flavour installed.
- bookwormMnot built on amd64/cloud-amd64, arm64/cloud-arm64, armhf/armmp, armhf/armmp-lpae, armhf/rt/armmp
- trixieMnot built on amd64/cloud-amd64, arm64/cloud-arm64, armel/rpi, armhf/armmp, armhf/armmp-lpae, armhf/rt/armmp, riscv64/riscv64, s390x/s390x
- forky, sidMnot built on amd64/cloud-amd64, arm64/cloud-arm64, armhf/armmp, armhf/armmp-lpae, loong64/loong64, riscv64/riscv64, s390x/s390x
- M
- a module where it is built at all; some flavours do not build it
- Build switch
- CONFIG_IPMI_HANDLER
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
- 7.8 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
- 0.12%, higher than 1.9% of all CVEssource
- CISA KEV
- not listedthe KEV catalogue
- Debian urgency
- unimportantsource
- 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 |
|---|---|---|
| 6.16 | 6.18.50 | 3088e41292fe |
| 6.16 | 7.2.4 | 5dc0b2a9af95 |
| 6.16 | 7.3 | 05ec76cfbce6 |
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 UAF is reached by close/release on /dev/ipmiN (ipmi_release → ipmi_destroy_user → _ipmi_destroy_user) after IPMICTL_REGISTER_FOR_CMD; BMC GET_MSG/IPMB/LAN command delivery is the RCU reader, not Linux network-packet processing, so the attack remains local like other /dev/ipmiN IPMI bugs.
- AC:LAttack complexity, low
- The attacker controls the free side (open, register-for-cmd, close) and arms command watching, then races close against GET_MSG/IPMB/LAN command handling they can induce via their own IPMI ioctls and typical host-to-BMC access; this is an attacker-driven UAF race, not a layout or victim-state condition.
- PR:LPrivileges required, low
- ipmi_open, ipmi_create_user, and IPMICTL_REGISTER_FOR_CMD perform no capable() check; access is only DAC on /dev/ipmiN, which server and appliance deployments routinely grant to a non-root ipmi/management group for ipmitool/freeipmi, matching established IPMI scoring.
- UI:NUser interaction, none
- The attacker opens, registers, and closes their own /dev/ipmiN file descriptors and issues ioctls themselves; no victim action such as mounting a filesystem or opening a hostile file is required.
- S:UScope, unchanged
- This is a host-kernel heap use-after-free of struct cmd_rcvr in the IPMI message handler; impact stays in the same OS security authority with no VM escape, IOMMU bypass, or sandbox boundary crossing.
- C:HConfidentiality impact, high
- Without synchronize_rcu(), find_cmd_rcvr() and handle_*_get_msg_cmd() read rcvr->user from a kmalloc'd cmd_rcvr that _ipmi_destroy_user() already kfree()d; reclaiming that object yields an attacker-controlled pointer and a kernel read primitive, so confidentiality is High per UAF guidance.
- I:HIntegrity impact, high
- A sprayed cmd_rcvr supplies a fake ipmi_user pointer; ipmi_alloc_recv_msg() then updates nr_msgs/refcount through that pointer and smi_work later invokes user->handler->ipmi_recv_hndl, enabling heap spray and control-flow hijack for arbitrary write and code execution.
- A:HAvailability impact, high
- Use-after-free of cmd_rcvr during the RCU list walk and the subsequent dangling user-pointer dereference readily oopses or panics the kernel under poisoning/KASAN, so availability impact is High per UAF guidance.