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CVE-2023-38691

MEDIUM
Published 2023-08-04T16:34:54.312Z
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CVSS Score

V3.1
5.0
/10
CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:C/C:L/I:N/A:N
Base Score Metrics
Exploitability: N/A Impact: N/A

EPSS Score

v2025.03.14
0.001
probability
of exploitation in the wild

There is a 0.1% chance that this vulnerability will be exploited in the wild within the next 30 days.

Updated: 2025-06-25
Exploit Probability
Percentile: 0.198
Higher than 19.8% of all CVEs

Attack Vector Metrics

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

Impact Metrics

Confidentiality
LOW
Integrity
NONE
Availability
NONE

Description

matrix-appservice-bridge provides an API for setting up bridges. Starting in version 4.0.0 and prior to versions 8.1.2 and 9.0.1, a malicious Matrix server can use a foreign user's MXID in an OpenID exchange, allowing a bad actor to impersonate users when using the provisioning API. The library does not check that the servername part of the `sub` parameter (containing the user's *claimed* MXID) is the the same as the servername we are talking to. A malicious actor could spin up a server on any given domain, respond with a `sub` parameter according to the user they want to act as and use the resulting token to perform provisioning requests. Versions 8.1.2 and 9.0.1 contain a patch. As a workaround, disable the provisioning API.

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:

>= 4.0.0, < 8.1.2 = 9.0.0

GitHub Security Advisories

Community-driven vulnerability intelligence from GitHub

✓ GitHub Reviewed MODERATE

matrix-appservice-bridge doesn't verify the sub parameter of an openId token exhange, allowing unauthorized access to provisioning APIs

GHSA-vc7j-h8xg-fv5x

Advisory Details

### Impact A malicious Matrix server can use a foreign user's MXID in an OpenID exchange, allowing a bad actor to impersonate users when using the provisioning API. ### Details The library does not check that the servername part of the `sub` parameter (containing the user's *claimed* MXID) is the same as the servername we are talking to. A malicious actor could spin up a server on any given domain, respond with a `sub` parameter according to the user they want to act as and use the resulting token to perform provisioning requests. ### Workarounds Disable the provisioning API. If the bridge does not use the provisioning API, you are not vulnerable.

Affected Packages

npm matrix-appservice-bridge
ECOSYSTEM: ≥4.0.0 <8.1.2
npm matrix-appservice-bridge
ECOSYSTEM: ≥9.0.0 <9.0.1

CVSS Scoring

CVSS Score

5.0

CVSS Vector

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

References

WEB https://github.com/matrix-org/matrix-appservice-bridge/security/advisories/GHSA-vc7j-h8xg-fv5x
ADVISORY https://nvd.nist.gov/vuln/detail/CVE-2023-38691
WEB https://github.com/matrix-org/matrix-appservice-bridge/commit/4c6723a5e7beda65cdf1ae5dbb882e8beaac8552
PACKAGE https://github.com/matrix-org/matrix-appservice-bridge

Advisory provided by GitHub Security Advisory Database. Published: August 4, 2023, Modified: August 4, 2023

References

https://github.com/matrix-org/matrix-appservice-bridge/security/advisories/GHSA-vc7j-h8xg-fv5x
https://github.com/matrix-org/matrix-appservice-bridge/commit/4c6723a5e7beda65cdf1ae5dbb882e8beaac8552
Published: 2023-08-04T16:34:54.312Z
Last Modified: 2024-10-07T13:01:29.642Z
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