Is CVE-2025-30355 in the CISA KEV catalog?

No. CVE-2025-30355 is not currently on the CISA Known Exploited Vulnerabilities list.

What is the CVSS severity of CVE-2025-30355?

CVE-2025-30355 has a CVSS v3 base score of 7.1 (HIGH).

What is the EPSS score for CVE-2025-30355?

CVE-2025-30355 has an EPSS score of 1.06% (60th percentile), estimating the probability of exploitation in the next 30 days.

CVE & CISA-KEV Catalog

CVE-2025-30355

HIGH

7.1

CVSS v3

NVD

Description

Synapse is an open source Matrix homeserver implementation. A malicious server can craft events which, when received, prevent Synapse version up to 1.127.0 from federating with other servers. The vulnerability has been exploited in the wild and has been fixed in Synapse v1.127.1. No known workarounds are available.

CWE-20Improper Input Validation

CVSS v3 Vector

Exploitability

Attack VectorNetwork

Attack ComplexityLow

Privileges RequiredLow

User InteractionNone

ScopeUnchanged

Impact

ConfidentialityNone

IntegrityLow

AvailabilityHigh

CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:L/A:H

Exploit Intelligence

1.06%probability of exploitation in 30 days

60thpercentile

Moderate risk: more likely to be exploited than 60% of all known CVEs.

References

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This product uses NVD data but is not endorsed or certified by the NVD. EPSS scores courtesy of FIRST.org (https://www.first.org/epss). Source: CISA KEV Catalog. Data as of 2025-08-26.