VYPR
Medium severityOSV Advisory· Published Oct 8, 2025· Updated Apr 15, 2026

CVE-2025-61672

CVE-2025-61672

Description

Synapse is an open source Matrix homeserver implementation. Lack of validation for device keys in Synapse before 1.138.3 and in Synapse 1.139.0 allow an attacker registered on the victim homeserver to degrade federation functionality, unpredictably breaking outbound federation to other homeservers. The issue is patched in Synapse 1.138.3, 1.138.4, 1.139.1, and 1.139.2. Note that even though 1.138.3 and 1.139.1 fix the vulnerability, they inadvertently introduced an unrelated regression. For this reason, the maintainers of Synapse recommend skipping these releases and upgrading straight to 1.138.4 and 1.139.2.

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Affected packages

Versions sourced from the GitHub Security Advisory.

PackageAffected versionsPatched versions
matrix-synapsePyPI
< 1.138.31.138.3
matrix-synapsePyPI
>= 1.139.0rc2, < 1.139.11.139.1

Affected products

3

Patches

Vulnerability mechanics

References

10

News mentions

0

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