# CVE-2022-39254

## Summary

- **CVE ID:** CVE-2022-39254
- **Severity:** HIGH
- **CVSS Score:** 8.6 (CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:N/I:H/A:N)
- **CWE:** CWE-322, CWE-287
- **Published:** Sep 29, 2022
- **Last Modified:** Mar 13, 2026

## 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.

## Affected Products

- poljar — matrix-nio (< 0.20)

## References

- [CNA](https://github.com/poljar/matrix-nio/security/advisories/GHSA-w4pr-4vjg-hffh)
- [CNA](https://github.com/poljar/matrix-nio/commit/b1cbf234a831daa160673defd596e6450e9c29f0)

## Exploitation Prediction (EPSS)

- **EPSS Score:** 0.23%
- **EPSS Percentile:** 45.9

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_Exported from OnDuty AI Vulnerability Intelligence on 2026-09-18._