Arch Linux Security Advisory ASA-202106-51 ========================================== Severity: Medium Date : 2021-06-22 CVE-ID : CVE-2021-32659 Package : matrix-appservice-irc Type : insufficient validation Remote : Yes Link : https://security.archlinux.org/AVG-2076 Summary ======= The package matrix-appservice-irc before version 0.27.0-1 is vulnerable to insufficient validation. Resolution ========== Upgrade to 0.27.0-1. # pacman -Syu "matrix-appservice-irc>=0.27.0-1" The problem has been fixed upstream in version 0.27.0. Workaround ========== As a workaround, disabling the automatic room upgrade handling can be done by removing the `roomUpgradeOpts` key from the `Bridge` class options. Description =========== In versions 2.6.0 and earlier of matrix-appservice-bridge, as included in matrix-appservice-irc before version 0.27.0, if a bridge has room upgrade handling turned on in the configuration (the `roomUpgradeOpts` key when instantiating a new `Bridge` instance.), any `m.room.tombstone` event it encounters will be used to unbridge the current room and bridge into the target room. However, the target room `m.room.create` event is not checked to verify if the `predecessor` field contains the previous room. This means that any malicious admin of a bridged room can repoint the traffic to a different room without the new room being aware. Versions 2.6.1 and greater are patched. As a workaround, disabling the automatic room upgrade handling can be done by removing the `roomUpgradeOpts` key from the `Bridge` class options. Impact ====== A malicious admin of a bridged room can repoint the traffic to a different room without the new room being aware. References ========== https://github.com/matrix-org/matrix-appservice-bridge/security/advisories/G... https://github.com/matrix-org/matrix-appservice-irc/releases/tag/0.27.0 https://github.com/matrix-org/matrix-appservice-bridge/pull/330 https://github.com/matrix-org/matrix-appservice-bridge/commit/b69e745584a34f... https://security.archlinux.org/CVE-2021-32659