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CVE-2026-53273
tee: optee: prevent use-after-free when the client exits before the supplicant
Published 2026-06-25 (4 months ago) by the Linux kernel CNA. Subsystem drivers/tee. Debian urgency: not yet assigned.
What to do, per Debian release
Debian's own status for CVE-2026-53273 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-4665-1 · 2026-07-03 · text | 6.1.176-1 | Update the kernel and reboot. DLA-4665-1 shipped the fix on 2026-07-03, in 6.1.176-1. A running kernel keeps the old code until the machine restarts. |
| Debian 13trixie | fixed | 6.12.94-1 | Update the kernel and reboot. Fixed in 6.12.94-1. A running kernel keeps the old code until the machine restarts. |
| Debian 14forky | fixed | 7.0.13-1 | Update the kernel and reboot. Fixed in 7.0.13-1. A running kernel keeps the old code until the machine restarts. |
| Debian unstablesid | fixed | 7.0.13-1 | Update the kernel and reboot. Fixed in 7.0.13-1. A running kernel keeps the old code until the machine restarts. |
The vulnerability
What the bug is
Commit 70b0d6b0a199 ("tee: optee: Fix supplicant wait loop") made the client wait as killable so it can be interrupted during shutdown or after a supplicant crash. This changes the original lifetime expectations: the client task can now terminate while the supplicant is still processing its request. If the client exits first it removes the request from its queue and kfree()s it, while the request ID remains in supp->idr. A subsequent lookup on the supplicant path then dereferences freed memory, leading to a use-after-free. Serialise access to the request with supp->mutex: * Hold supp->mutex in optee_supp_recv() and optee_supp_send() while looking up and touching the request. * Let optee_supp_thrd_req() notice that the client has terminated and signal optee_supp_send() accordingly. With these changes the request cannot be freed while the supplicant still has a reference, eliminating the race.
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/tee/optee/supp.c
- What this is
- OP-TEE DRIVERMAINTAINERS section matched on drivers/tee/optee/ · op-tee@lists.trustedfirmware.org · Maintained
- Kernel module
- optee
Check it on the machine
grep -wE 'CONFIG_OPTEE|CONFIG_TEE' /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 opteePrints 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/amd64, amd64/cloud-amd64, amd64/rt/amd64, armhf/armmp, armhf/armmp-lpae, armhf/rt/armmp, i386/686, i386/686-pae, i386/rt/686-pae, ppc64el/powerpc64le
- trixieMnot built on amd64/amd64, amd64/cloud-amd64, amd64/rt/amd64, armel/rpi, armhf/armmp, armhf/armmp-lpae, armhf/rt/armmp, ppc64el/powerpc64le, ppc64el/powerpc64le-64k, riscv64/riscv64, s390x/s390x
- forky, sidMnot built on amd64/amd64, amd64/cloud-amd64, amd64/rt-amd64, armhf/armmp, armhf/armmp-lpae, loong64/loong64, ppc64el/powerpc64le, ppc64el/powerpc64le-64k, riscv64/riscv64, s390x/s390x
- M
- a module where it is built at all; some flavours do not build it
- Build switches
- CONFIG_OPTEE, CONFIG_TEE
- 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
- 2026-06-25 (4 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
- 0.12%, higher than 1.6% of all CVEssource
- CISA KEV
- not listedthe KEV catalogue
- Debian urgency
- not yet assignedsource
- Subsystem
- drivers/tee
Upstream fixes
The versions the CNA records as introducing and fixing this, and the commit for each. source
| Introduced | Fixed in | Commit |
|---|---|---|
| 5.10.235 | 5.10.259 | 416259cb5bff |
| 5.15.179 | 5.15.210 | 724d0caffd42 |
| 6.1.130 | 6.1.176 | ae847ab29ded |
| 6.6.80 | 6.6.143 | 9a0dc9279d09 |
| 6.12.17 | 6.12.94 | d366a01475f9 |
| 6.14 | 6.18.36 | d5b57bb314d7 |
| 6.14 | 7.0.13 | 373152c94e57 |
| 6.14 | 7.1 | 387a926ee166 |
| 5.4.291 | 0 | 0 |
| 6.13.5 | 0 | 0 |
Debian advisories
| Advisory | Date | Shipped to | Debian |
|---|---|---|---|
| DLA-4671-1 | 2026-07-05 | bullseye 6.1.176-1~deb11u1 | tracker |
| DLA-4665-1 | 2026-07-03 | bookworm 6.1.176-1 | tracker |
| DLA-4664-1 | 2026-07-03 | bullseye 5.10.259-1 | 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 vulnerable path is reached through local TEE character device ioctls where a client request enters OP-TEE and is later completed by tee-supplicant via TEE_IOC_SUPPL_SEND. It is not directly reachable from network packets.
- AC:LAttack complexity, low
- The attacker can create supplicant-backed OP-TEE requests and interrupt or terminate the waiting client while the supplicant is processing them. This race is attacker-triggerable and repeatable rather than dependent on rare external conditions.
- PR:LPrivileges required, low
- A basic local user can reach the non-privileged TEE client ioctl path and rely on the legitimate system tee-supplicant to complete the request. The privileged supplicant device exists, but attacker control of it is not required to trigger the UAF.
- UI:NUser interaction, none
- No victim user action is needed after the attacker runs the local client and triggers the ioctl/race sequence. The supplicant daemon processes queued requests automatically.
- S:UScope, unchanged
- The memory corruption occurs in the normal-world kernel OP-TEE driver and affects the same kernel security authority. This is a standard local kernel compromise path, not a VM escape or separate security-scope bypass.
- C:HConfidentiality impact, high
- The stale IDR entry points to a freed optee_supp_req that is later dereferenced by optee_supp_send. As a use-after-free in kernel heap memory, it can plausibly be shaped into disclosure of arbitrary kernel memory.
- I:HIntegrity impact, high
- The supplicant completion path writes through fields of the freed request, including the request parameter pointer and completion state. This kernel UAF can plausibly be exploited for controlled memory corruption and privilege escalation.
- A:HAvailability impact, high
- Even without full exploitation, dereferencing and updating a freed kernel object can readily cause an oops, panic, or hang. The bug is repeatedly triggerable from a local client while supplicant requests are in flight.