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.
CVE-2025-61672
“—” beside the score: it is equal to the CVSS score beside it.
This medium-severity CVE scores 5.3 under a secondary CVSS source (NVD's own analysis pending). EPSS exploit probability: 0.5% (41st percentile of EPSS-scored CVEs). No GitHub Security Advisory CVSS is on record for this CVE.
Also known asEUVD-2025-33305 (ENISA EUVD) · GHSA-fh66-fcv5-jjfr (GitHub Security Advisories) · PYSEC-2026-1612 (OSV.dev)Source: ENISA EUVD
- Lower severity and no public exploit yet
A fix is available — apply it.
- CVSS v3
- 5.3
- EG Score
- 5.3MEDIUMmedium confidence
- EG Risk
- 24EG Risk 24/100
EG Risk is EchelonGraph's 0–100 priority score. It fuses impact severity (EG Severity, the CVSS base score, never the KEV-floored or EPSS-lifted EG Score) with real-world exploitation and automatability, under weights EchelonGraph set by hand, so you can rank equal-severity CVEs and fix the most dangerous first. Higher = act sooner.
How it’s computed (value × EchelonGraph’s weight)Severity53% × 45%Impact severity (EG Severity): CVSS 5.3 of 10. Never the KEV-floored or EPSS-lifted EG Score.Exploitation0.5% × 40%FIRST EPSS: the 30-day exploitation probability when EchelonGraph scored this CVE.Automatability0% × 15%CISA's SSVC Automatable value: no (Vulnrichment).SSVC (CISA's decision table, applied by EchelonGraph): Track at every mission impact level.Exploitation none (CISA Vulnrichment) · Automatable no (CISA Vulnrichment) · Technical impact partial (CISA Vulnrichment). All three are CISA's SSVC values (Vulnrichment). EchelonGraph applied CISA's decision table to them; CISA publishes SSVC inputs and the table, not a decision for each CVE.Action: A fix is available. Apply it within your standard update timelines. - EPSS PROB
- 0.5%
- EPSS %ILE
- 41st
- KEV
- Not listed
What the EG score is made of (scorer v4.0: the three questions the 0–10 score mixes, published apart · methodology)
The EG score (5.3): severity, escalated by confirmed exploitation. This CVE's 5.3 is its impact severity (EG Severity), not escalated.
- EG Severity
- 5.3 MEDIUMCVSS-B, impact only: no KEV listing, EPSS or EG-KEV tier raises it.a secondary CVSS source · CVSS v3.0 or v3.1
- EG Likelihood
- 0.5% within 30 daysSource: FIRST EPSS (model v2026.06.15, score date 2026-10-31). FIRST's exploitation probability, not an EchelonGraph model.
- Confirmed exploitation
- None on record (CISA KEV, EG-KEV Tier 1)Reported apart from the likelihood: an observed fact, not a probability.
- EG Priority
- SSVC Track at medium mission impactTrack at every mission impact level.CISA BOD 26-04: 60 days if the affected system is publicly exposed; Fix on system upgrade if it is not.Each input and its source, and whom BOD 26-04 binds: the SSVC and BOD 26-04 blocks below.
SSVC (CISA's decision table, applied by EchelonGraph)Track 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). All three are CISA's SSVC values (Vulnrichment). EchelonGraph applied CISA's decision table to them; CISA publishes SSVC inputs and the table, not a decision for each CVE. Mission impact is CISA's Mission & Well-being decision point, and only you can judge it. CISA's table makes it high when Mission Prevalence is Essential — the vulnerable component "directly provides capabilities that constitute at least one MEF for at least one entity" (MEF: mission essential function) — or when Public Well-Being Impact is Irreversible: "multiple fatalities are likely", the cyber-physical system "is likely lost or destroyed", "extreme or serious externalities" are imposed on other parties, or social systems such as elections or the financial grid "are destabilized and potentially collapse". CISA's decision table
BOD 26-04 (CISA's remediation timeline, Table 1)60 days if the affected system is publicly exposed; Fix on system upgrade if it is not.
The score's inputs: In CISA KEV no (CISA's KEV catalog) · Automatable no (CISA Vulnrichment) · Technical impact partial (CISA Vulnrichment). Whether your system is publicly exposed is yours to answer. BOD 26-04 binds US Federal Civilian Executive Branch agencies; for anyone else it is CISA's published timeline, a reference rather than an obligation. The directive · how EchelonGraph applies it
Published
October 8, 2025
Last Modified
October 8, 2026
Advisory Details (6)
Auto-updated Oct 8, 2026Invalid device keys degrade federation functionality · Advisory · element-hq/synapse · GitHub
https://github.com/element-hq/synapse/security/advisories/GHSA-fh66-fcv5-jjfrv1.139.1
Patch available: element-hq/synapse v1.139.1
https://github.com/element-hq/synapse/releases/tag/v1.139.1v1.138.3
Patch available: element-hq/synapse v1.138.3
https://github.com/element-hq/synapse/releases/tag/v1.138.3Validate 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/17097commit 7069636c2d6d (element-hq/synapse)
Fix landed in element-hq/synapse commit 7069636c2d6d — awaiting tagged release
https://github.com/element-hq/synapse/commit/7069636c2d6d1ef2022287addf3ed8b919ef2740commit 26aaaf9e48ff (element-hq/synapse)
Fix landed in element-hq/synapse commit 26aaaf9e48ff — awaiting tagged release
https://github.com/element-hq/synapse/commit/26aaaf9e48fff80cf67a20c691c75d670034b3c1Patch Availability(2)
| Vendor / Ecosystem | Fix (by version range) / Patch | Released | Source |
|---|---|---|---|
| pip | matrix-synapse @ 1.138.3 (fixes < 1.138.3) | — | ghsa |
| pip | matrix-synapse @ 1.139.1 (fixes >= 1.139.0rc2, < 1.139.1) | — | ghsa |
Patches are aggregated from vendor advisories (Red Hat, Microsoft, Cisco, GitHub) and package ecosystems (OSV, GHSA). Multiple rows for the same upstream release have been deduplicated.
Affected Packages
(2 across 2 ecosystems)
Debian:14(1)
| Package | Vulnerable range | Fix by version range | Dependents |
|---|---|---|---|
| matrix-synapse | 0.19.2+dfsg-3 ... 1.99.0-3 (305 versions) |
| — |
PyPI(1)
| Package | Vulnerable range | Fix by version range | Dependents |
|---|---|---|---|
| matrix-synapse | 0.33.5 ... 1.99.0rc1 (464 versions) |
| — |
Weakness Classification(1)
MITRE Common Weakness Enumeration — the root-cause categories this CVE belongs to.
Data Freshness Timeline
(refreshed 10× in last 7d / 41× in last 30d)
Each row is a time one of our pipelines fetched, updated or re-scored this CVE. 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. An arrow marks a change the record states ("CVSS v3 → 9.1"); EPSS and GHSA rows show the values recorded at that time, not what changed (EPSS values are rounded; hover one for the exact figures). Most recent first.
Showing the most recent 95 of 223 refreshes on record for this CVE.
A repeat, a row identical to one the same pipeline wrote less than 10 seconds earlier, is not a separate refresh and is not counted. 5 repeat rows among the latest 100 are merged into the row they repeat. The 128 oldest rows on record are not shown and were not checked, so the counts can still include repeats.
- 2026-11-02 16:43 UTCEPSS rescoreEPSS 0.5% · 41st percentile
- 2026-11-01 16:33 UTCEPSS rescoreEPSS 0.5% · 41st percentile
- 2026-11-01 08:02 UTCGHSA enrichmentGHSA-fh66-fcv5-jjfr · GitHub severity MODERATE
- 2026-11-01 08:02 UTCEG score recompute
- 2026-10-31 20:25 UTCOSV refresh
- 2026-10-31 16:31 UTCEPSS rescoreEPSS 0.5% · 41st percentile
- 2026-10-30 16:33 UTCEPSS rescoreEPSS 0.5% · 41st percentile
- 2026-10-29 16:32 UTCEPSS rescoreEPSS 0.5% · 41st percentile
- 2026-10-28 16:30 UTCEPSS rescoreEPSS 0.5% · 41st percentile
- 2026-10-27 16:30 UTCEPSS rescoreEPSS 0.5% · 40th percentile
- 2026-10-26 16:30 UTCEPSS rescoreEPSS 0.5% · 40th percentile
- 2026-10-25 16:31 UTCEPSS rescoreEPSS 0.5% · 40th percentile
- 2026-10-25 16:14 UTCEG score recompute
- 2026-10-24 16:31 UTCEPSS rescoreEPSS 0.5% · 39th percentile
- 2026-10-23 16:30 UTCEPSS rescoreEPSS 0.5% · 39th percentile
- 2026-10-23 14:18 UTCEG score recompute
- 2026-10-22 16:33 UTCEPSS rescoreEPSS 0.5% · 39th percentile
- 2026-10-21 16:31 UTCEPSS rescoreEPSS 0.5% · 39th percentile
- 2026-10-20 16:31 UTCEPSS rescoreEPSS 0.5% · 39th percentile
- 2026-10-19 16:31 UTCEPSS rescoreEPSS 0.5% · 38th percentile
- 2026-10-18 16:31 UTCEPSS rescoreEPSS 0.5% · 38th percentile
- 2026-10-18 05:22 UTCEG score recompute
- 2026-10-17 16:33 UTCEPSS rescoreEPSS 0.5% · 38th percentile
- 2026-10-16 16:39 UTCEPSS rescoreEPSS 0.5% · 38th percentile
- 2026-10-15 16:31 UTCEPSS rescoreEPSS 0.5% · 38th percentile
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- 2026-10-14 16:31 UTCEPSS rescoreEPSS 0.5% · 38th percentile
- 2026-10-13 16:33 UTCEPSS rescoreEPSS 0.5% · 38th percentile
- 2026-10-12 16:52 UTCEG score recompute
- 2026-10-12 16:33 UTCEPSS rescoreEPSS 0.5% · 38th percentile
- 2026-10-11 20:26 UTCEG score recompute
- 2026-10-11 18:38 UTCEG score recompute
- 2026-10-11 15:13 UTCEG score recompute
- 2026-10-11 13:47 UTCEPSS rescoreEPSS 0.5% · 38th percentile
- 2026-10-10 19:59 UTCEPSS rescoreEPSS 0.5% · 38th percentile
- 2026-10-09 20:06 UTCEPSS rescoreEPSS 0.5% · 38th percentile
- 2026-10-08 17:10 UTCEPSS rescoreEPSS 0.5% · 38th percentile
- 2026-10-08 15:09 UTCEG score recompute
- 2026-10-07 23:47 UTCEPSS rescoreEPSS 0.5% · 38th percentile
- 2026-10-06 15:17 UTCEPSS rescoreEPSS 0.5% · 38th percentile
- 2026-10-05 17:42 UTCEPSS rescoreEPSS 0.5% · 38th percentile
- 2026-10-04 23:21 UTCEPSS rescoreEPSS 0.5% · 38th percentile
- 2026-10-03 14:25 UTCEPSS rescoreEPSS 0.5% · 38th percentile
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- 2026-09-28 13:50 UTCEPSS rescoreEPSS 0.5% · 37th percentile
- 2026-09-26 15:58 UTCEPSS rescoreEPSS 0.5% · 37th percentile
- 2026-09-24 14:02 UTCEPSS rescoreEPSS 0.5% · 37th percentile
- 2026-09-23 13:47 UTCEPSS rescoreEPSS 0.5% · 39th percentile
- 2026-09-21 04:19 UTCOSV refresh
- 2026-09-20 20:15 UTCEPSS rescoreEPSS 0.5% · 39th percentile
- 2026-09-19 15:42 UTCEPSS rescoreEPSS 0.5% · 39th percentile
- 2026-09-18 19:27 UTCEPSS rescoreEPSS 0.5% · 39th percentile
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- 2026-09-16 14:07 UTCEPSS rescoreEPSS 0.5% · 39th percentile
- 2026-09-15 03:10 UTCEPSS rescoreEPSS 0.5% · 39th percentile
- 2026-09-13 16:46 UTCEPSS rescoreEPSS 0.5% · 38th percentile
- 2026-09-12 15:00 UTCEPSS rescoreEPSS 0.5% · 39th percentile
- 2026-09-11 14:52 UTCEPSS rescoreEPSS 0.5% · 38th percentile
- 2026-09-11 09:36 UTCEPSS rescoreEPSS 0.5% · 38th percentile
- 2026-09-10 09:34 UTCEPSS rescoreEPSS 0.5% · 38th percentile
- 2026-09-08 22:00 UTCEPSS rescoreEPSS 0.5% · 38th percentile
- 2026-09-07 16:00 UTCEPSS rescoreEPSS 0.4% · 36th percentile
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- 2026-09-02 14:11 UTCEPSS rescoreEPSS 0.4% · 36th percentile
- 2026-09-02 02:38 UTCOSV refresh
- 2026-09-01 13:53 UTCEPSS rescoreEPSS 0.4% · 36th percentile
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- 2026-08-24 14:16 UTCEPSS rescoreEPSS 0.4% · 35th percentile
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- 2026-08-16 05:29 UTCOSV refresh
- 2026-08-16 02:13 UTCEPSS rescoreEPSS 0.4% · 36th percentile
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Related CVEs(same product + same CWE)
Same product
10 shownDebian:14:matrix-synapse
Frequently asked(5)
What is CVE-2025-61672?
When was the CVE record for CVE-2025-61672 published?
Is CVE-2025-61672 actively exploited?
What is the CVSS score of CVE-2025-61672?
How do I remediate CVE-2025-61672?
Dependency Blast Radius
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