# CVE-2021-47202: thermal: Fix NULL pointer dereferences in of_thermal_ functions

> A local attacker can trigger a kernel crash by writing to thermal zone sysfs attributes when the associated sensor is not yet probed.

- **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:** 10 Apr 2024
- **Updated:** 11 May 2026
- **Also known as:** DEBIAN-CVE-2021-47202, GHSA-w6pp-7vhg-w878, UBUNTU-CVE-2021-47202

## What is CVE-2021-47202?

CVE-2021-47202 is a medium-severity vulnerability in Linux kernel, published on 10 Apr 2024. 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:

thermal: Fix NULL pointer dereferences in of_thermal_ functions

of_parse_thermal_zones() parses the thermal-zones node and registers a
thermal_zone device for each subnode. However, if a thermal zone is
consuming a thermal sensor and that thermal sensor device hasn't probed
yet, an attempt to set trip_point_*_temp for that thermal zone device
can cause a NULL pointer dereference. Fix it.

 console:/sys/class/thermal/thermal_zone87 # echo 120000 > trip_point_0_temp
 ...
 Unable to handle kernel NULL pointer dereference at virtual address 0000000000000020
 ...
 Call trace:
  of_thermal_set_trip_temp+0x40/0xc4
  trip_point_temp_store+0xc0/0x1dc
  dev_attr_store+0x38/0x88
  sysfs_kf_write+0x64/0xc0
  kernfs_fop_write_iter+0x108/0x1d0
  vfs_write+0x2f4/0x368
  ksys_write+0x7c/0xec
  __arm64_sys_write+0x20/0x30
  el0_svc_common.llvm.7279915941325364641+0xbc/0x1bc
  do_el0_svc+0x28/0xa0
  el0_svc+0x14/0x24
  el0_sync_handler+0x88/0xec
  el0_sync+0x1c0/0x200

While at it, fix the possible NULL pointer dereference in other
functions as well: of_thermal_get_temp(), of_thermal_set_emul_temp(),
of_thermal_get_trend().

Weakness: CWE-476 (NULL Pointer Dereference)

## Which versions are affected by CVE-2021-47202?

It affects 1 product.


Products: Linux kernel.

## How do I fix CVE-2021-47202?

Apply the vendor's patch.

## Is CVE-2021-47202 being exploited?

There is no known exploitation of CVE-2021-47202 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-2021-47202 and fix it if it is affected.

What it is: CVE-2021-47202 is a medium-severity vulnerability in Linux kernel, published on 10 Apr 2024. 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-2021-47202 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-2021-47202/ (Markdown: https://insights.sbomify.com/CVE-2021-47202/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2021-47202
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2021-47202
- OSV: https://osv.dev/vulnerability/CVE-2021-47202

---
From sbomify Insights: https://insights.sbomify.com/CVE-2021-47202/
Summaries are generated and may contain mistakes; the official description above is the record.