CVE-2025-61672

MEDIUMPre-NVD 5.35.3—
EchelonGraph scoreMEDIUM confidence

This medium-severity CVE scores 5.3 under a secondary CVSS source (NVD's own analysis pending). EPSS exploit probability: 0.5% (38th percentile of EPSS-scored CVEs). GitHub Security Advisory data not yet ingested — confidence will rise once GHSA publishes (typical lag: hours to days for open-source ecosystem CVEs; never for infrastructure-only CVEs).

Triggered by: NVD CVSS baseline
Sources: epss, secondary
5.3EG
EchelonGraph verdictMonitorLow exploitation likelihood right now — keep watching.
  • Lower severity and no public exploit yet
CISA-KEV: Not listedEPSS PROB: 0.5%CVSS: 5.3Exploit: None knownExposed services: Not assessed

A fix is available — apply it.

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 v3
5.3
EG Score
5.3MEDIUMmedium confidence
EG Risk
24
EG Risk 24/100CISA SSVC

EG Risk is EchelonGraph's 0–100 priority score: it fuses intrinsic severity with real-world exploitation and automatability so you can rank equal-severity CVEs and fix the most dangerous first. Higher = act sooner. Distinct from the 0–10 EG Score (severity).

How it’s computed
Severity53% × 45%
Exploitation0% × 40%
Automatability0% × 15%
CISA SSVC: Track at every mission impact level.
Action: A fix is available. Apply it within your standard update timelines.
EPSS PROB
0.5%
EPSS %ILE
38th
KEV
Not listed

CISA SSVCTrack at every mission impact level.

A fix is available. Apply it within your standard update timelines.

Exploitation none (CISA Vulnrichment) · Automatable no (CISA Vulnrichment) · Technical impact partial (CISA Vulnrichment). Mission impact is CISA's Mission & Well-being decision point, and only you can judge it: high means the affected system is essential to your organisation's mission, or its compromise could cause irreversible harm to people. CISA's decision table

Published

October 8, 2025

Last Modified

October 8, 2026

Advisory Details (6)

Auto-updated Oct 8, 2026
Patch available. Sources: github_commit, github_pr, github_release, github.
githubMentions a patch (unverified)

Invalid device keys degrade federation functionality · Advisory · element-hq/synapse · GitHub

https://github.com/element-hq/synapse/security/advisories/GHSA-fh66-fcv5-jjfr
github_release Patch Available

v1.139.1

Patch available: element-hq/synapse v1.139.1

https://github.com/element-hq/synapse/releases/tag/v1.139.1
github_release Patch Available

v1.138.3

Patch available: element-hq/synapse v1.138.3

https://github.com/element-hq/synapse/releases/tag/v1.138.3
github_pr

Validate the body of requests to `/keys/upload`

Fix merged in element-hq/synapse PR #17097 on 2025-10-07 — awaiting tagged release

https://github.com/element-hq/synapse/pull/17097
github_commit

commit 7069636c2d6d (element-hq/synapse)

Fix landed in element-hq/synapse commit 7069636c2d6d — awaiting tagged release

https://github.com/element-hq/synapse/commit/7069636c2d6d1ef2022287addf3ed8b919ef2740
github_commit

commit 26aaaf9e48ff (element-hq/synapse)

Fix landed in element-hq/synapse commit 26aaaf9e48ff — awaiting tagged release

https://github.com/element-hq/synapse/commit/26aaaf9e48fff80cf67a20c691c75d670034b3c1

Affected Packages

(2 across 2 ecosystems)
Debian:14(1)
PackageVulnerable rangeFix by version rangeDependents
matrix-synapse0.19.2+dfsg-3 ... 1.99.0-3 (305 versions)
  • every version up to 1.139.2-1: fixed in 1.139.2-1
—
PyPI(1)
PackageVulnerable rangeFix by version rangeDependents
matrix-synapse0.33.5 ... 1.99.0rc1 (464 versions)
  • every version up to 1.138.3: fixed in 1.138.3
  • 1.139.0rc2 up to 1.139.1: fixed in 1.139.1
—

Weakness Classification(1)

MITRE Common Weakness Enumeration — the root-cause categories this CVE belongs to.

Data Freshness Timeline

(refreshed 8× in last 7d / 28× in last 30d)

Each row is a source pipeline that fetched or updated this CVE on that date, with what changed. For example, "NVD update" means NVD published or revised its analysis for this CVE; "MITRE cvelistV5" means we ingested or refreshed it from the CNA feed. Most recent first.

Showing the most recent 100 of 194 total refreshes for this CVE.

  1. 2026-10-09 20:06 UTCEPSS rescore
  2. 2026-10-08 17:10 UTCEPSS rescore
  3. 2026-10-08 15:09 UTCEG score recompute
  4. 2026-10-07 23:47 UTCEPSS rescore
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  18. 2026-09-21 04:19 UTCOSV refresh
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  1. 2026-09-12 15:00 UTCEPSS rescore
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  10. 2026-09-02 02:38 UTCOSV refresh
  11. 2026-09-01 13:53 UTCEPSS rescore
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  25. 2026-08-16 14:55 UTCEPSS rescore
  26. 2026-08-16 05:29 UTCOSV refresh
  27. 2026-08-16 02:13 UTCEPSS rescore
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  30. 2026-08-13 21:59 UTCEPSS rescore
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  41. 2026-08-04 15:09 UTCEPSS rescore
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  44. 2026-08-02 02:26 UTCEPSS rescore
  45. 2026-08-01 04:15 UTCEPSS rescore
  46. 2026-07-31 22:42 UTCOSV refresh
  47. 2026-07-30 16:27 UTCEPSS rescore
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  49. 2026-07-28 15:35 UTCEPSS rescore
  50. 2026-07-27 14:12 UTCEPSS rescore
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  56. 2026-07-23 14:18 UTCEPSS rescore
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  58. 2026-07-23 03:00 UTCEG score recompute
  59. 2026-07-22 14:08 UTCEPSS rescore
  60. 2026-07-21 15:24 UTCEPSS rescore
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  68. 2026-07-15 01:59 UTCEPSS rescore
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  70. 2026-07-14 05:55 UTCOSV refresh
  71. 2026-07-13 22:29 UTCEPSS rescore
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  73. 2026-07-12 05:46 UTCEPSS rescore
  74. 2026-07-11 08:27 UTCEPSS rescore
  75. 2026-07-09 19:09 UTCEPSS rescore

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Frequently asked(5)

What is CVE-2025-61672?
CVE-2025-61672 is a medium vulnerability published on October 8, 2025. 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.…
When was CVE-2025-61672 disclosed?
CVE-2025-61672 was first published on October 8, 2025, with the most recent update on October 8, 2026. EchelonGraph re-ingests CVE updates from NVD on a 2-hour cycle, so this page reflects the latest published state.
Is CVE-2025-61672 actively exploited?
CVE-2025-61672 is not currently on CISA's Known Exploited Vulnerabilities catalog. FIRST EPSS estimates a 0.5% probability of exploitation in the next 30 days (38th percentile of EPSS-scored CVEs).
What is the CVSS score of CVE-2025-61672?
CVE-2025-61672 has a CVSS base score of 5.3 (a secondary CVSS source that NVD displays; NVD's own analysis pending).
How do I remediate CVE-2025-61672?
A fix for CVE-2025-61672 is available: update to the fixed version the vendor names in its advisory.

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