CVE-2021-32659
This means that any malicious admin of a bridged room can repoint the traffic to a different room without the new room being aware.
Does this matter?
Lower severity and a low EPSS score (0.94%). Track it; it rarely justifies an emergency change on its own.
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.
- CVSS 3.1
- 4.9 MEDIUMCVSS:3.1/AV:N/AC:L/PR:H/UI:N/S:U/C:N/I:H/A:N
- EPSS
- 0.94% probability · 59th percentile
- CISA KEV
- Not listed
- Weakness
- CWE-306
- Affected
- matrix/matrix-appservice-bridge
- Source
- security-advisories@github.com
References
- https://github.com/matrix-org/matrix-appservice-bridge/commit/b69e745584a34fcfd858df33e4631e420da07b9fPatch, Third Party Advisory
- https://github.com/matrix-org/matrix-appservice-bridge/releases/tag/2.6.1Patch, Third Party Advisory
- https://github.com/matrix-org/matrix-appservice-bridge/security/advisories/GHSA-35g4-qx3c-vjhxMitigation, Third Party Advisory
- https://github.com/matrix-org/matrix-appservice-bridge/commit/b69e745584a34fcfd858df33e4631e420da07b9fPatch, Third Party Advisory
- https://github.com/matrix-org/matrix-appservice-bridge/releases/tag/2.6.1Patch, Third Party Advisory
- https://github.com/matrix-org/matrix-appservice-bridge/security/advisories/GHSA-35g4-qx3c-vjhxMitigation, Third Party Advisory
Source: NVD record, EPSS from FIRST.org, KEV from CISA. Refreshed daily.