5.3

CVE-2025-61672: element-hq synapse

CVSS: 5.3v4.0MediumDeferred
AliasesGHSA-fh66-fcv5-jjfrPYSEC-2026-1612UBUNTU-CVE-2025-61672
Published 08-10-2025Last modified 15-10-2025
Open JSON

Vulnerability summary

CVE-2025-61672 is a medium (CVSS 5.3) vulnerability in element-hq synapse. EPSS estimates a 0.47% chance of exploitation in the next 30 days, higher than 38.9% of scored vulnerabilities.

Overall risk
21/100
0100
Low · default modelHow is this calculated?
CVSS score
5.3/10
010
Medium · v4.0 (CVE.org)
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. 08-10-2025
    PublishedVulnerability first disclosed.
  2. 15-10-2025
    Last modifiedVulnerability information updated.

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.

CVSS metrics

5 scores · 5 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 19-09-2026

19-09-202619-10-2026
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

Debian1 product
  • matrix-synapse< 1.139.2-1
Element-hq1 product
Opensuse1 product
  • matrix-synapse&distro=openSUSE Tumbleweed< 1.139.1-1.1
PyPI1 product
  • matrix-synapse< 1.138.3 | ≥ 1.139.0rc2, < 1.139.1
Ubuntu1 product
  • matrix-synapseAll versions (No fix recorded)

5 vendors · 5 products

References

16 links
Show all 16 references