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Back to active CVEs
Unknown severity · Source severity not reportedCVE-2025-66622GHSA-JJ6P-3M75-G2P3

matrix-sdk-base: Denial of service due to custom `m.room.join_rules` eventsCVE-2025-66622

Answer in brief

CVE-2025-66622 records a Unknown severity vulnerability in matrix-sdk-base: Denial of service due to custom `m.room.join_rules` events. The current sources do not mark it as known exploited. The current feed maps matrix-sdk-base (crates.io). Check affected ranges and fixed versions before updating.

Analysis pending evidence review

HOL Guard separates source facts from reviewed analysis. See the methodology.

Published Dec 8, 2025Updated Oct 12, 2026Source checked Oct 12, 2026First seen by HOL Oct 12, 2026Material review Oct 12, 2026
Upstream Advisory

Key facts

Risk
Unknown severitySource severity not reported
Exploitation
Not marked as known exploited
Affected software
1 mapped package or product
Fix availability
Available

Why this deserves its current priority

A CVSS score is not reported in the current record. The current sources do not mark it as known exploited. Treat this as a source-backed prioritization signal, not a statement about your environment.

Analysis status

Analysis pending evidence review

Factual feed record only; HOL analysis is not approved for indexing. Read the methodology.

Affected scope and exposure questions

The current feed maps matrix-sdk-base (crates.io). Check affected ranges and fixed versions before updating.

Mapped affected packages and fixed versions
PackageAffected rangeFixed version
matrix-sdk-basecrates.io>=0.0.0-0 <0.16.00.16.0

Recommended response

  1. 1Check inventory. Check lockfiles and deployed manifests for matrix-sdk-base.
  2. 2Review the reported fix. Update matrix-sdk-base to 0.16.0 if you use the affected versions. Test the change in a non-production environment first.

Evidence timeline and material changes

  1. Published upstream

    Dec 8, 2025

    Evidence: source:osv:source_dates:source-dates:record

  2. Source modified

    Oct 12, 2026

    Evidence: source:osv:source_dates:source-dates:record

  3. First seen by HOL

    Oct 12, 2026

Sources and claim methodology

  • Source referencecrates.io
  • GitHub security advisorygithub.com
  • Source referencerustsec.org
Upstream source description

The matrix-sdk-base crate is 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.

Quoted source text, attributed separately from HOL analysis.

Record context

Vulnerability class
Vulnerability
EPSS
Not reported
CWE IDs
Not reported
Source
OSV
Source checked
Oct 12, 2026
References
3 linked sources
Open source record