Automatic room upgrade handling can be used maliciously to bridge a room non-consentually
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 software
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| Platform | Package | Vulnerable versions | Fixed in |
|---|---|---|---|
| npm package | matrix-appservice-bridge | < 2.6.1 | 2.6.1 |
References
- https://github.com/matrix-org/matrix-appservice-bridge/security/advisories/GHSA-35g4-qx3c-vjhx
- https://nvd.nist.gov/vuln/detail/CVE-2021-32659
- https://github.com/matrix-org/matrix-appservice-bridge/pull/330
- https://github.com/matrix-org/matrix-appservice-bridge/commit/b69e745584a34fcfd858df33e4631e420da07b9f
- https://github.com/matrix-org/matrix-appservice-bridge/releases/tag/2.6.1
- CVSS vector
CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:N/A:N- Weakness (CWE)
CWE-306- Platform
- npm
- Package
matrix-appservice-bridge- Disclosed
- 21.06.2021
- Updated
- 11.10.2026 10:22
Sources and licenses
OSV / GitHub Advisory Database - GHSA-35g4-qx3c-vjhx - CC BY 4.0
Vulnerability history: matrix-appservice-bridge
All published vulnerabilities of this package (npm package), newest first. Shows whether this is a one-off slip or a package that needs watching.
- Total entries
- 2
- First → latest
- 06.2021 08.2023
- Without a fix
- 0
- Exploited in attacks
- 0
Severity breakdown
- Medium 2
Disclosures per year
- 2021: 1
- 2022: 0
- 2023: 1
- 2024: 0
- 2025: 0
- 2026: 0
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Automatic room upgrade handling can be used maliciously to bridge a room non-consentually this entry
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