6.5

CVE-2023-38691: matrix-org matrix-appservice-bridge Improper Authentication

CVSS: 6.5v3.1MediumModified
AliasesGHSA-vc7j-h8xg-fv5x
Published 04-08-2023Last modified 07-10-2024
Open JSON

Vulnerability summary

CVE-2023-38691 is a medium (CVSS 6.5) Improper Authentication vulnerability in matrix-org matrix-appservice-bridge. EPSS estimates a 0.47% chance of exploitation in the next 30 days, higher than 39% of scored vulnerabilities.

Overall risk
26/100
0100
Medium · default modelHow is this calculated?
CVSS score
6.5/10
010
Medium · v3.1 (NVD)
EPSS score
0.47%
0%100%
Low · 0.00 pp in 30 days
KEVNot listedIn no KEV catalog
RansomwareNone recordedNo known use recorded
Public exploits0No public exploits recorded

Timeline

  1. 04-08-2023
    PublishedVulnerability first disclosed.
  2. 07-10-2024
    Last modifiedVulnerability information updated.

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.

CVSS metrics

3 scores · 3 sources · 1 version

EPSS trend

Probability

0.47%

Chance of exploitation in the next 30 days

Percentile

39%

Versus all other CVEs

30-day change

0.00 pp

From 0.47% on 20-09-2026

20-09-202620-10-2026
EPSS score
0.47%

Known exploited

Compare KEV catalogs

Not in any of the 3 tracked catalogs.

Public exploits

0 found

No public exploits indexed.

Weaknesses

CWE · root cause

Affected systems

Matrix1 product
Matrix-org1 product
Npm1 product
  • matrix-appservice-bridge≥ 4.0.0, < 8.1.2 | ≥ 9.0.0, < 9.0.1

3 vendors · 3 products

References

4 links