---
id: CVE-2025-66622
title: matrix-sdk-base is the base component to build a Matrix client library
summary: >-
  matrix-sdk-base is the base component to build a Matrix client library.
  Versions 0.14.1 and prior are unable to handle responses that include custom
  m.room.join_rules values due to a serialization bug. This can be exploited to
  cause a de…
severity: high
cvss: 7.5
cvssVector: 'CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H'
cwe:
  - CWE-755
vendor: matrix
product: matrix-rust-sdk
affected:
  - matrix-rust-sdk < 0.16.0
patched:
  - matrix-rust-sdk 0.16.0
published: '2025-12-09'
updated: '2026-10-07'
sourceUpdated: '2026-10-07T20:10:01.970'
source: NVD
sourceUrl: 'https://nvd.nist.gov/vuln/detail/CVE-2025-66622'
references:
  - url: >-
      https://github.com/matrix-org/matrix-rust-sdk/commit/4ea0418abefab2aa93f8851a4d39c723e703e6b0
    label: security-advisories@github.com
  - url: 'https://github.com/matrix-org/matrix-rust-sdk/pull/5924'
    label: security-advisories@github.com
  - url: >-
      https://github.com/matrix-org/matrix-rust-sdk/security/advisories/GHSA-jj6p-3m75-g2p3
    label: security-advisories@github.com
  - url: 'https://rustsec.org/advisories/RUSTSEC-2025-0135.html'
    label: security-advisories@github.com
tags:
  - nvd
epss: 0.00413
epssPercentile: 0.33413
ingestedAt: '2026-10-07T20:46:46.829Z'
---

## Overview

matrix-sdk-base is the base component to build a Matrix client library. Versions 0.14.1 and prior are unable to handle responses that include custom m.room.join_rules values due to a serialization bug. This can be exploited to cause a denial-of-service condition, if a user is invited to a room with non-standard join rules, the crate's sync process will stall, preventing further processing for all rooms. This is fixed in version 0.16.0.

## Affected

- `matrix-rust-sdk < 0.16.0`

## Remediation

Upgrade past the affected range:

- `matrix-rust-sdk 0.16.0`