CVE-2024-39691 Information

Description

matrix-appservice-irc is a Node.js IRC bridge for the Matrix messaging protocol. The fix for GHSA-wm4w-7h2q-3pf7 / CVE-2024-32000 included in matrix-appservice-irc 2.0.0 relied on the Matrix homeserver-provided timestamp to determine whether a user has access to the event they’re replying to when determining whether or not to include a truncated version of the original event in the IRC message. Since this value is controlled by external entities a malicious Matrix homeserver joined to a room in which a matrix-appservice-irc bridge instance (before version 2.0.1) is present can fabricate the timestamp with the intent of tricking the bridge into leaking room messages the homeserver should not have access to. matrix-appservice-irc 2.0.1 drops the reliance on origin_server_ts when determining whether or not an event should be visible to a user instead tracking the event timestamps internally. As a workaround it’s possible to limit the amount of information leaked by setting a reply template that doesn’t contain the original message.

Reference

https://github.com/matrix-org/matrix-appservice-irc/security/advisories/GHSA-w9mh-5x8j-9754 https://github.com/matrix-org/matrix-appservice-irc/pull/1804 https://github.com/matrix-org/matrix-appservice-irc/commit/1835e047f269001054be4c68867797aa12372a0f https://github.com/matrix-org/matrix-appservice-irc/blob/d5d67d1d3ea3f0f6962a0af2cc57b56af3ad2129/config.sample.yaml#L601-L604