CVE-2024-42369: A room with itself as a its predecessor will freeze matrix-js-sdk

Severity: medium (CVSS 5.3 v3.1)
Exploited in the wild: not listed in CISA KEV
EPSS: 0.5% probability of exploitation in the next 30 days
Public exploit or detection template: none known
Published: 2024-08-20 · updated 2026-06-17
Weakness: CWE-674

Description

matrix-js-sdk is a Matrix messaging protocol Client-Server SDK for JavaScript. A malicious homeserver can craft a room or room structure such that the predecessors form a cycle. The matrix-js-sdk's getRoomUpgradeHistory function will infinitely recurse in this case, causing the code to hang. This method is public but also called by the 'leaveRoomChain()' method, so leaving a room will also trigger the bug. This was patched in matrix-js-sdk 34.3.1.

Affected products

matrix-org matrix-js-sdk: before 34.3.1 — fixed in 34.3.1

How to fix

Upgrade to a fixed version: matrix-org matrix-js-sdk 34.3.1. Check the vendor advisory for mitigations.

References

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