CVE-2025-616725.3MediumCWE-1287

CVE-2025-61672: Synapse: Invalid device keys degrade federation functionality

element-hq · synapse

Affected: element-hq synapse · Exploitation: unlikely (under 1%)

Not in CyberSIXT coverage yet: no article names this CVE. This page shows the public record.

0.5%probability of exploitation in the next 30 days

41st percentile

050100

Higher than 41% of scored CVEs

5.3MediumCVSS 4.0

LowMediumHighCrit.

DescriptionCVE.org

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.

Affected products1

From the CVE record. A product or version that is not listed is unknown, not unaffected.

element-hq · synapse< 1.138.3; = 1.139.0

On the Atlas

Every published CVE is on the CyberSIXT Atlas, grouped by weakness, vendor and month.

Open the Atlas

Exploitation: Unlikely (under 1%). EPSS under 1%, or no score yet.
CISA KEV: Not listed
Public check: No public nuclei template
Weakness: Improper Validation of Specified Type of Input · Input Validation and Logic
Vendor: element-hq
Published: October 2025
Band: Unlikely (under 1%), October 2025

CoverageNo articles yet

No CyberSIXT article names CVE-2025-61672 yet, so there is no coverage timeline, action brief or change log for it. Everything on this page comes from the public CVE record, CISA KEV, EPSS and the nuclei template index. Search the archive or see the CVEs in the news.