CVE-2021-32659
Automatic room upgrade handling can be used maliciously to bridge a room non-consentually
Impact
### Impact 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 mailcious admin of a bridged room can repoint the traffic to a different room without the new room being aware. ### Patches Versions 2.6.1 and greater are patched. ### Workarounds Disabling the automatic room upgrade handling can be done by removing the `roomUpgradeOpts` key from the `Bridge` class options. ### References The issue is patched by https://github.com/matrix-org/matrix-appservice-bridge/pull/330 ### For more information] If you have any questions or comments about this advisory, email us at security@matrix.org.
Affected packages
| Ecosystem | Package | Affected | Fixed in |
|---|---|---|---|
| npm | matrix-appservice-bridge | < 2.6.1 | 2.6.1 |
Affected products
| Vendor | Product | Affected versions |
|---|---|---|
| Matrix | Matrix-Appservice-Bridge | before 2.6.1 |
Weakness classification
References
- NVD record
- CVE.org record
- GitHub advisory
- https://github.com/matrix-org/matrix-appservice-bridge/commit/b69e745584a34fcfd858df33e4631e420da07b9f
- https://github.com/matrix-org/matrix-appservice-bridge/releases/tag/2.6.1
- https://github.com/matrix-org/matrix-appservice-bridge/security/advisories/GHSA-35g4-qx3c-vjhx
- https://github.com/advisories/GHSA-35g4-qx3c-vjhx
- https://nvd.nist.gov/vuln/detail/CVE-2021-32659
- https://github.com/matrix-org/matrix-appservice-bridge/pull/330