CVE-2025-66622: RUSTSEC-2025-0135 - matrix-sdk-base: Denial of service due to custom `m.room.join_rules` events

CVE-2025-66622 · Severity: high · CVSS 7.5 · Published 2025-12-09

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.

Vendors: crates.io, Matrix.

Quick answers

Is CVE-2025-66622 exploited in the wild?
No. Junglewise Threat Intelligence has no report of CVE-2025-66622 being exploited in the wild.
How severe is CVE-2025-66622?
High severity, with a CVSS score of 7.5, published 9 December 2025.
Which products and versions are affected?
matrix-sdk-base (crates.io) SEMVER:introduced=0,fixed=0.16.0, SEMVER:introduced=0.0.0-0,fixed=0.16.0.
Is there a fix for CVE-2025-66622?
Yes. matrix-sdk-base (crates.io): upgrade to 0.16.0 or later. Junglewise finds every place you run it, drafts the upgrade and applies it once you approve.
Am I affected by CVE-2025-66622?
Check whether you run matrix-sdk-base (crates.io) or Matrix-Rust-Sdk at an affected version. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.

How to fix

  • matrix-sdk-base (crates.io): upgrade to 0.16.0 or later
    cargo update -p matrix-sdk-base

Affected products

  • matrix-sdk-base (crates.io) SEMVER:introduced=0,fixed=0.16.0, SEMVER:introduced=0.0.0-0,fixed=0.16.0
  • Matrix-Rust-Sdk

Identifiers

  • CVE-2025-66622
  • GHSA-jj6p-3m75-g2p3
  • RUSTSEC-2025-0135

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