Vulnerability · Published Jun 16, 2021 · Assigned by GitHub_M
CVE-2021-32659Automatic room upgrade handling can be used maliciously to bridge a room non-consentually
Medium 6.5
In plain English
A medium-severity missing authentication in matrix-appservice-bridge from matrix-org. There are no confirmed reports of exploitation so far. The chance it is exploited in the next 30 days is estimated at 0.9% (higher than 61% of all known vulnerabilities). Fixed versions are available - upgrade the affected package.
Official 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 packages & fixed versions
| Ecosystem | Package | Fixed in | Advisory |
|---|---|---|---|
| npm | matrix-appservice-bridge | 2.6.1 | GHSA-35g4-qx3c-vjhx |
Affected products (as reported)
| Vendor | Product | Versions |
|---|---|---|
| matrix-org | matrix-appservice-bridge | < 2.6.1 |
Weakness: CWE-306 · Vector: CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:N/A:N
References
- https://github.com/matrix-org/matrix-appservice-bridge/security/advisories/GHSA-35g4-qx3c-vjhx x_refsource_CONFIRM
- https://github.com/matrix-org/matrix-appservice-bridge/commit/b69e745584a34fcfd858df33e4631e420da07b9f x_refsource_MISC
- https://github.com/matrix-org/matrix-appservice-bridge/releases/tag/2.6.1 x_refsource_MISC