CVE-2025-66622

matrix-sdk-base is vulnerable to DoS via custom m.room.join_rules event values

HIGH
7.5
CVSS Score
Published: December 9, 2025 at 02:07 AM UTC
Updated: October 7, 2026 at 08:10 PM UTC
2 products affected across 2 vendorsMatrix Rust SDKMatrix Rust SDK

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Severity
HIGH7.5
Exploit prediction
EPSS 0.4%
SSVC
No known exploit

Description

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

Our own answer: ranges merged, affected separated from platform-only, with confidence and review flags.

v < 0.16.0
Affected range stops below 0.16.0, so it looks safe — our inference, not a vendor statement

References (4)

x_refsource_MISCIssue TrackingPatch
Source: cverecord
https://github.com/matrix-org/matrix-rust-sdk/pull/5924
x_refsource_MISCThird Party Advisory
Source: cverecord
https://rustsec.org/advisories/RUSTSEC-2025-0135.html

SSVC — Action Prioritization

SSVCNo known exploitAutomatablePartial impact

SSVC signals action urgency (what to patch first), separate from CVSS which measures severity.

CVSS

Attack Vector
NETWORK
Complexity
LOW
Privileges
NONE
User Interaction
NONE
Scope
UNCHANGED
Confidentiality
NONE
Integrity
NONE
Availability
HIGH
Vector?

Quick Info

StatusANALYZED
CWE
CWE-755

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