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CVE-2026-89899
media: cec: disable delayed work before freeing an interrupted transmit
Published 2026-09-16 (33 days ago) by the Linux kernel CNA. Subsystem drivers/media. Debian urgency: not yet assigned.
What to do, per Debian release
Debian's own status for CVE-2026-89899 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 | vulnerable | 6.1.190-1 | No fix published anywhere yet, neither in Debian nor upstream for the series bookworm tracks. Watch the Debian tracker page for this CVE. Advisories for bookworm have historically landed a median of 23 days after publication. |
| 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
cec_transmit_msg_fh() drops adap->lock to wait for a blocking transmit in wait_for_completion_killable(). If that wait is interrupted by a signal, cancel_delayed_work_sync() can run before the CEC kthread arms the reply timeout via schedule_delayed_work(&data->work) in cec_transmit_done_ts(). The work is then armed after the cancel, and the data is freed with its delayed_work still pending: ODEBUG: free active (active state 0) object: ... hint: cec_wait_timeout Use disable_delayed_work_sync(): it cancels the work and disables it, so the later schedule_delayed_work() becomes a no-op and the work cannot be re-armed. The data is freed right after, so it need not be re-enabled.
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/media/cec/core/cec-adap.c
- What this is
- CEC FRAMEWORKMAINTAINERS section matched on drivers/media/cec/ · linux-media@vger.kernel.org · Supported
- Kernel module
- cec
Check it on the machine
grep -w CONFIG_CEC_CORE /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 cecPrints 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.
- bookworm, trixie, forky, sid, bookworm · linux-6.12Mnot built on arm64/cloud-arm64
- M
- a module where it is built at all; some flavours do not build it
- Build switch
- CONFIG_CEC_CORE
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
- 2026-09-16 (33 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
- 0.16%, higher than 5.2% of all CVEssource
- CISA KEV
- not listedthe KEV catalogue
- Debian urgency
- not yet assignedsource
- Subsystem
- drivers/media
Upstream fixes
The versions the CNA records as introducing and fixing this, and the commit for each. source
| Introduced | Fixed in | Commit |
|---|---|---|
| 4.20 | 6.12.110 | 9a951931d4b4 |
| 4.20 | 6.18.51 | a3adb63b1219 |
| 4.20 | 7.2.5 | 9c6ceb094922 |
| 4.20 | 7.3 | 0fbd5c232702 |
| 4.18.19 | 0 | 0 |
| 4.19.2 | 0 | 0 |
Debian advisories
| Advisory | Date | Shipped to | Debian |
|---|---|---|---|
| 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 UAF is in cec_transmit_msg_fh(), reached only via the local CEC_TRANSMIT ioctl on /dev/cec* (cec_ioctl to cec_transmit). A CEC peer on the HDMI bus cannot signal-interrupt wait_for_completion_killable(), so this is Local, unlike CEC RX IRQ bugs scored Adjacent.
- AC:LAttack complexity, low
- The attacker issues a blocking CEC_TRANSMIT with a reply timeout and signals their own thread so cancel_delayed_work_sync() races the CEC kthread arming data->work in cec_transmit_done_ts(). They control both sides and can retry; syzkaller triggered it.
- PR:LPrivileges required, low
- cec_open() defaults to CEC_MODE_INITIATOR, and neither CEC_TRANSMIT nor CEC_ADAP_S_LOG_ADDRS calls capable(). Only raw mode needs CAP_SYS_RAWIO and monitor modes need CAP_NET_ADMIN, neither required here. Unprivileged users with /dev/cec (video group, uaccess, Android HDMI-CEC) can trigger it.
- UI:NUser interaction, none
- The attacker opens /dev/cec, configures logical addresses, issues the blocking transmit ioctl, and delivers a signal to their own process. No separate victim action is required.
- S:UScope, unchanged
- The use-after-free corrupts kernel heap (struct cec_data) in the host kernel. It does not cross a VM, IOMMU, or other separate security authority.
- C:HConfidentiality impact, high
- cec_wait_timeout() runs on a kmalloc'd struct cec_data after kfree(), so a sprayed replacement object yields an attacker-controlled adap pointer and list walks. Per kernel CNA guidance, use-after-free is High confidentiality.
- I:HIntegrity impact, high
- The delayed-work UAF lets the attacker spray struct cec_data and corrupt list_heads and the adapter mutex when cec_wait_timeout()/cec_data_cancel() run, enabling arbitrary write and control-flow hijack. Per kernel CNA guidance, use-after-free is High integrity.
- A:HAvailability impact, high
- Freeing struct cec_data while its delayed_work is still pending causes cec_wait_timeout() to run on freed memory, producing a kernel oops or panic even without a full exploit. Per kernel CNA guidance, use-after-free is High availability.