CVEvulnerability

CVE-2021-32659

4.9 MEDIUM Published 2021-06-16 Modified 2026-06-17 Official page ↗
Status
Modified
Published
2021-06-16
Last modified
2026-06-17
Assigner
[email protected]
CVSS 3.1 ([email protected])
6.5 MEDIUM — CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:N/A:N
CVSS 3.1 ([email protected])
4.9 MEDIUM — CVSS:3.1/AV:N/AC:L/PR:H/UI:N/S:U/C:N/I:H/A:N
CVSS 2.0 ([email protected])
3.5 LOW — AV:N/AC:M/Au:S/C:N/I:P/A:N
Weaknesses
CWE-306

Description

Matrix-appservice-bridge is the bridging service for the Matrix communication program's application services. In versions 2.6.0 and earlier, 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.

Affected configurations

• matrix matrix-appservice-bridge (< 2.6.1)

Related

Weakness · CWE (1)

  • CWE-306 Missing Authentication for Critical Functionality weakness

References