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CVE-2021-32659

MEDIUM
Published 2021-06-16T18:45:11
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Expert Analysis

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CVSS Score

V3.1
6.5
/10
CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:N/A:N
Base Score Metrics
Exploitability: N/A Impact: N/A

EPSS Score

v2025.03.14
0.003
probability
of exploitation in the wild

There is a 0.3% chance that this vulnerability will be exploited in the wild within the next 30 days.

Updated: 2025-06-25
Exploit Probability
Percentile: 0.500
Higher than 50.0% of all CVEs

Attack Vector Metrics

Attack Vector
NETWORK
Attack Complexity
LOW
Privileges Required
LOW
User Interaction
NONE
Scope
UNCHANGED

Impact Metrics

Confidentiality
HIGH
Integrity
NONE
Availability
NONE

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.

Available Exploits

No exploits available for this CVE.

Related News

No news articles found for this CVE.

Affected Products

matrix-org

matrix-appservice-bridge

Affected Versions:

< 2.6.1

GitHub Security Advisories

Community-driven vulnerability intelligence from GitHub

✓ GitHub Reviewed MODERATE

Automatic room upgrade handling can be used maliciously to bridge a room non-consentually

GHSA-35g4-qx3c-vjhx

Advisory Details

### 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 [email protected].

Affected Packages

npm matrix-appservice-bridge
ECOSYSTEM: ≥0 <2.6.1

CVSS Scoring

CVSS Score

5.0

CVSS Vector

CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:N/A:N

References

WEB https://github.com/matrix-org/matrix-appservice-bridge/security/advisories/GHSA-35g4-qx3c-vjhx
ADVISORY https://nvd.nist.gov/vuln/detail/CVE-2021-32659
WEB https://github.com/matrix-org/matrix-appservice-bridge/pull/330
WEB https://github.com/matrix-org/matrix-appservice-bridge/commit/b69e745584a34fcfd858df33e4631e420da07b9f
WEB https://github.com/matrix-org/matrix-appservice-bridge/releases/tag/2.6.1

Advisory provided by GitHub Security Advisory Database. Published: June 21, 2021, Modified: June 16, 2021

References

https://github.com/matrix-org/matrix-appservice-bridge/security/advisories/GHSA-35g4-qx3c-vjhx
https://github.com/matrix-org/matrix-appservice-bridge/commit/b69e745584a34fcfd858df33e4631e420da07b9f
https://github.com/matrix-org/matrix-appservice-bridge/releases/tag/2.6.1
Published: 2021-06-16T18:45:11
Last Modified: 2024-08-03T23:25:31.074Z
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