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.
Published 2021-06-16 19:15:39
Updated 2021-07-09 19:46:45
Source GitHub, Inc.
View at NVD,   CVE.org

Exploit prediction scoring system (EPSS) score for CVE-2021-32659

0.14%
Probability of exploitation activity in the next 30 days EPSS Score History
~ 49 %
Percentile, the proportion of vulnerabilities that are scored at or less

CVSS scores for CVE-2021-32659

Base Score Base Severity CVSS Vector Exploitability Score Impact Score Score Source First Seen
3.5
LOW AV:N/AC:M/Au:S/C:N/I:P/A:N
6.8
2.9
NIST
4.9
MEDIUM CVSS:3.1/AV:N/AC:L/PR:H/UI:N/S:U/C:N/I:H/A:N
1.2
3.6
NIST
6.5
MEDIUM CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:N/A:N
2.8
3.6
GitHub, Inc.

CWE ids for CVE-2021-32659

  • The product does not perform any authentication for functionality that requires a provable user identity or consumes a significant amount of resources.
    Assigned by: security-advisories@github.com (Primary)

References for CVE-2021-32659

Products affected by CVE-2021-32659

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