# CVE-2025-21871: tee: optee: Fix supplicant wait loop

> A flaw in the Linux kernel OP-TEE driver allows a hung or crashed user-space daemon to cause a system hang, requiring a hard reboot.

- **Severity:** Medium 5.5 (`CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H`)
- **Exploited in the wild:** Not known
- **Login needed:** Any signed-in user
- **Attackable:** Local or same network only
- **Victim action needed:** Not needed
- **Fix available:** Yes
- **Published:** 27 Mar 2025
- **Updated:** 11 May 2026
- **Also known as:** BELL-CVE-2025-21871, DEBIAN-CVE-2025-21871, GHSA-gggq-j347-r3w6, ROOT-OS-UBUNTU-2404-CVE-2025-21871, UBUNTU-CVE-2025-21871

## What is CVE-2025-21871?

CVE-2025-21871 is a medium-severity denial of service vulnerability in Linux kernel, published on 27 Mar 2025. It can only be exploited from the same machine or local network, with no action from the victim.

### Official description

In the Linux kernel, the following vulnerability has been resolved:

tee: optee: Fix supplicant wait loop

OP-TEE supplicant is a user-space daemon and it's possible for it
be hung or crashed or killed in the middle of processing an OP-TEE
RPC call. It becomes more complicated when there is incorrect shutdown
ordering of the supplicant process vs the OP-TEE client application which
can eventually lead to system hang-up waiting for the closure of the
client application.

Allow the client process waiting in kernel for supplicant response to
be killed rather than indefinitely waiting in an unkillable state. Also,
a normal uninterruptible wait should not have resulted in the hung-task
watchdog getting triggered, but the endless loop would.

This fixes issues observed during system reboot/shutdown when supplicant
got hung for some reason or gets crashed/killed which lead to client
getting hung in an unkillable state. It in turn lead to system being in
hung up state requiring hard power off/on to recover.

Weakness: CWE-835 (Loop with Unreachable Exit Condition)

## Which versions are affected by CVE-2025-21871?

It affects 1 product.


Products: Linux kernel.

## How do I fix CVE-2025-21871?

Apply the vendor's patch.

## Is CVE-2025-21871 being exploited?

There is no known exploitation of CVE-2025-21871 in the wild and no public exploit code.

## Other vulnerabilities in Linux kernel

- [CVE-2026-53266](https://insights.sbomify.com/CVE-2026-53266/): Linux Kernel Out-of-Bounds Write (high 8.8, exploited in the wild)
- [CVE-2013-6282](https://insights.sbomify.com/CVE-2013-6282/): Linux Kernel Improper Input Validation (high 8.8, exploited in the wild)
- [CVE-2022-0185](https://insights.sbomify.com/CVE-2022-0185/): Linux Kernel Heap-Based Buffer Overflow (high 8.4, exploited in the wild)
- [CVE-2013-2094](https://insights.sbomify.com/CVE-2013-2094/): Linux Kernel Privilege Escalation (high 8.4, exploited in the wild)
- [CVE-2026-53362](https://insights.sbomify.com/CVE-2026-53362/): Linux Kernel Unspecified (high 7.8, exploited in the wild)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2025-21871 and fix it if it is affected.

What it is: CVE-2025-21871 is a medium-severity denial of service vulnerability in Linux kernel, published on 27 Mar 2025. It can only be exploited from the same machine or local network, with no action from the victim.
Exploitation: There is no known exploitation of CVE-2025-21871 in the wild and no public exploit code.

Affected product: Linux kernel. No package-level version data is available, so check the vendor advisory linked from the reference page.

Task:
1. Search the dependency manifests and lockfiles (for example package.json, package-lock.json, requirements.txt, poetry.lock, uv.lock, pom.xml, build.gradle, go.mod, Cargo.lock, Gemfile.lock) and any Dockerfiles for the affected packages, including transitive dependencies.
2. If an affected version is in use, upgrade it to the fixed version for its release line with the project's package manager, so the lockfile is regenerated. Prefer the smallest upgrade that fixes it.
3. If there is no fix, or the upgrade would break the build, do not guess: explain the risk and the safest workaround instead.
4. Run the tests and summarise what changed and why.
5. If nothing in the project is affected, say so and change nothing.

Reference: https://insights.sbomify.com/CVE-2025-21871/ (Markdown: https://insights.sbomify.com/CVE-2025-21871/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2025-21871
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2025-21871
- OSV: https://osv.dev/vulnerability/CVE-2025-21871

---
From sbomify Insights: https://insights.sbomify.com/CVE-2025-21871/
Summaries are generated and may contain mistakes; the official description above is the record.