# CVE-2022-39254: When matrix-nio receives forwarded room keys, the receiver doesn't check if it requested the key from the forwarder

> Attackers can impersonate users by inserting invalid room keys because the client fails to verify the key's origin, compromising encrypted communication integrity.

- **Severity:** High 8.6 (`CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:N/I:H/A:N`)
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Over the internet
- **Victim action needed:** Not needed
- **Fix available:** Yes
- **Published:** 29 Sep 2022
- **Updated:** 23 Apr 2025
- **Also known as:** DEBIAN-CVE-2022-39254, GHSA-w4pr-4vjg-hffh, PYSEC-2026-842, UBUNTU-CVE-2022-39254

## What is CVE-2022-39254?

CVE-2022-39254 is a high-severity authentication bypass vulnerability in poljar matrix-nio, published on 29 Sep 2022. An attacker can exploit it over the internet without logging in, with no action from the victim.

### Official description

matrix-nio is a Python Matrix client library, designed according to sans I/O principles. Prior to version 0.20, when a users requests a room key from their devices, the software correctly remember the request. Once they receive a forwarded room key, they accept it without checking who the room key came from. This allows homeservers to try to insert room keys of questionable validity, potentially mounting an impersonation attack. Version 0.20 fixes the issue.

Weakness: CWE-322 (Key Exchange without Entity Authentication), CWE-287 (Improper Authentication)

## Which versions are affected by CVE-2022-39254?

3 open source packages ship an affected version, including matrix-nio. It affects 1 product.


| Package | Ecosystem | Affected | Fixed in |
| --- | --- | --- | --- |
| `matrix-nio` | PyPI | All versions | 0.20 |
| `matrix-nio` | PyPI | All versions | 0.20 |
| `matrix-nio` | PyPI | All versions | 0.20 |

Products: Matrix-Nio Project Matrix-Nio.

## How do I fix CVE-2022-39254?

Upgrade matrix-nio to 0.20 or later.

## Is CVE-2022-39254 being exploited?

There is no known exploitation of CVE-2022-39254 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2022-39254 and fix it if it is affected.

What it is: CVE-2022-39254 is a high-severity authentication bypass vulnerability in poljar matrix-nio, published on 29 Sep 2022. An attacker can exploit it over the internet without logging in, with no action from the victim.
Exploitation: There is no known exploitation of CVE-2022-39254 in the wild and no public exploit code.

Affected packages and fixed versions:
- matrix-nio (PyPI): affected all versions; fixed in 0.20
- matrix-nio (PyPI): affected all versions; fixed in 0.20
- matrix-nio (PyPI): affected all versions; fixed in 0.20

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-2022-39254/ (Markdown: https://insights.sbomify.com/CVE-2022-39254/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2022-39254
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2022-39254
- OSV: https://osv.dev/vulnerability/CVE-2022-39254

---
From sbomify Insights: https://insights.sbomify.com/CVE-2022-39254/
Summaries are generated and may contain mistakes; the official description above is the record.