CVE-2025-30355 json
Synapse vulnerable to federation denial of service via malformed events
published 2025-03-27 19 mo ago modified 2026-07-07 4 mo ago also EUVD-2025-8265 , GHSA-v56r-hwv5-mxg6 , PYSEC-2026-1614
- cvss
- 7.1
- version 3.1, CNA
- cisa kev
- Not listed
- not in CISA's catalog
- epss
- 1.2%
- EPSS 1.2% chance of exploitation in 30 days, percentile 69%
- public exploits
- 0
- none known
Summary
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.
Patch / fix
- pypi matrix-synapse 1.127.1
- element-hq synapse 1.127.1
- element synapse 1.127.1
- matrix synapse 1.127.1
- matrix-synapse openSUSE Tumbleweed 1.127.1-1.1
opensuse advisories openSUSE-SU-2025:14939-1
- synapse Alpine 3.24, Alpine 3.23, Alpine 3.22 +1 more 1.127.1-r0
alpine advisories ALPINE-CVE-2025-30355
Alpine secdb © Alpine Linux, from https://secdb.alpinelinux.org via OSV; changed: normalised to fixed package versions per release. CC BY-SA 4.0
CISA SSVC
- Exploitation
- none
- Automatable
- no
- Technical impact
- partial
- Assessed
- 19 mo ago
Exploit prediction
1.23% chance of exploitation in the next 30 days, higher than 69% of all scored CVEs (FIRST EPSS, 2026-11-08).
CVSS scores
| assigned by | version | score | vector |
|---|---|---|---|
| CNA | 3.1 | 7.1 | CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:L/A:H |
| GitHub | 3.1 | 7.1 | CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:L/A:H |
| NVD | 3.1 | 7.5 | CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H |
| OSV | 3.1 | 7.1 | CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:L/A:H |
Affected packages
| ecosystem | package | affected | fixed in |
|---|---|---|---|
| pypi | matrix-synapse | <1.127.1 |
1.127.1 |
Affected products
- element-hq synapse
Classification
- Weakness
-
- CWE-20 Improper Input Validation
References
-
github.com
/element-hq/synapse/commit/2277df2a1eb685f85040ef98fa21d41aa4cdd389
web, patch
-
github.com
/element-hq/synapse/security/advisories/GHSA-v56r-hwv5-mxg6
web, vendor-advisory
-
github.com
/element-hq/synapse/releases/tag/v1.127.1
web, release-notes
-
nvd.nist.gov
/vuln/detail/CVE-2025-30355
advisory
-
github.com
/element-hq/synapse
package
-
pypi.org
/project/matrix-synapse
package
-
github.com
/advisories/GHSA-v56r-hwv5-mxg6
advisory
Sources
- CVE List CVE-2025-30355
- GitHub Advisory GHSA-v56r-hwv5-mxg6
- NVD CVE-2025-30355
- OSV PYSEC-2026-1614
Fencer Vulns keeps one entry per vulnerability: the CVE id wins, then GHSA, and records that alias each other are merged, except that two CVEs always keep separate entries. The same data is available as JSON.
CPEs and fixed versions use Anchore's correction of NVD's data: Added CPE configurations because not yet analyzed by NVD.