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SSRF in Sydent due to missing validation of hostnames

High severity GitHub Reviewed Published Apr 15, 2021 in matrix-org/sydent • Updated Feb 1, 2023

Package

pip matrix-sydent (pip)

Affected versions

< 2.3.0

Patched versions

2.3.0

Description

Impact

Sydent can be induced to send HTTP GET requests to internal systems, due to lack of parameter validation or IP address blacklisting.

It is not possible to exfiltrate data or control request headers, but it might be possible to use the attack to perform an internal port enumeration.

Patches

Fixed in 9e57334, 8936925, 3d531ed, 0f00412

Workarounds

A potential workaround would be to use a firewall to ensure that Sydent cannot reach internal HTTP resources.

For more information

If you have any questions or comments about this advisory, email us at security@matrix.org.

References

@richvdh richvdh published to matrix-org/sydent Apr 15, 2021
Reviewed Apr 15, 2021
Published by the National Vulnerability Database Apr 15, 2021
Published to the GitHub Advisory Database Apr 19, 2021
Last updated Feb 1, 2023

Severity

High

CVSS overall score

This score calculates overall vulnerability severity from 0 to 10 and is based on the Common Vulnerability Scoring System (CVSS).
/ 10

CVSS v3 base metrics

Attack vector
Network
Attack complexity
Low
Privileges required
Low
User interaction
None
Scope
Changed
Confidentiality
High
Integrity
None
Availability
None

CVSS v3 base metrics

Attack vector: More severe the more the remote (logically and physically) an attacker can be in order to exploit the vulnerability.
Attack complexity: More severe for the least complex attacks.
Privileges required: More severe if no privileges are required.
User interaction: More severe when no user interaction is required.
Scope: More severe when a scope change occurs, e.g. one vulnerable component impacts resources in components beyond its security scope.
Confidentiality: More severe when loss of data confidentiality is highest, measuring the level of data access available to an unauthorized user.
Integrity: More severe when loss of data integrity is the highest, measuring the consequence of data modification possible by an unauthorized user.
Availability: More severe when the loss of impacted component availability is highest.
CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:C/C:H/I:N/A:N

EPSS score

0.103%
(43rd percentile)

Weaknesses

CVE ID

CVE-2021-29431

GHSA ID

GHSA-9jhm-8m8c-c3f4

Source code

No known source code
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