What’s Vulnerable › Vulnerabilities

CVE-2025-66622: matrix-sdk-base is vulnerable to DoS via custom m.room.join_rules event values

• Severity: high (CVSS 7.5 v3.1)
• Exploited in the wild: not listed in CISA KEV
• EPSS: 0.4% probability of exploitation in the next 30 days
• Public exploit or detection template: none known
• Published: 2025-12-09 · updated 2026-10-07
• Weakness: CWE-755

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 products

• matrix-org matrix-rust-sdk: before 0.16.0 — fixed in 0.16.0

How to fix

Upgrade to a fixed version: matrix-org matrix-rust-sdk 0.16.0. Check the vendor advisory for mitigations.

References

• https://github.com/matrix-org/matrix-rust-sdk/commit/4ea0418abefab2aa93f8851a4d39c723e703e6b0
• https://github.com/matrix-org/matrix-rust-sdk/pull/5924
• https://github.com/matrix-org/matrix-rust-sdk/security/advisories/GHSA-jj6p-3m75-g2p3
• https://rustsec.org/advisories/RUSTSEC-2025-0135.html

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