CVE-2025-30355: Synapse vulnerable to federation denial of service via malformed events
First published: Thu Mar 27 2025(Updated: )
### Impact 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. ### Patches Fixed in Synapse v1.127.1. ### Workarounds Closed federation environments of trusted servers or non-federating installations are not affected. ### For more information If you have any questions or comments about this advisory, please email us at [security at element.io](mailto:security@element.io).
Credit: security-advisories@github.com
| Affected Software | Affected Version | How to fix |
|---|---|---|
| pip/matrix-synapse | <1.127.1 | 1.127.1 |
| Synapse | <1.127.0 |
Never miss a vulnerability like this again
Sign up to SecAlerts for real-time vulnerability data matched to your software, aggregated from hundreds of sources.
Reference Links
- https://github.com/element-hq/synapse/security/advisories/GHSA-v56r-hwv5-mxg6
- https://github.com/element-hq/synapse/commit/2277df2a1eb685f85040ef98fa21d41aa4cdd389
- https://github.com/element-hq/synapse/releases/tag/v1.127.1
- https://nvd.nist.gov/vuln/detail/CVE-2025-30355
- https://github.com/advisories/GHSA-v56r-hwv5-mxg6 (Advisory)
Frequently Asked Questions
What is the severity of CVE-2025-30355?
CVE-2025-30355 is classified as a high severity vulnerability due to its potential to disrupt federated communications in Synapse.
How do I fix CVE-2025-30355?
To fix CVE-2025-30355, update Synapse to version 1.127.1 or later.
What versions of Synapse are affected by CVE-2025-30355?
CVE-2025-30355 affects Synapse versions up to and including 1.127.0.
What are the implications of CVE-2025-30355 being exploited?
If exploited, CVE-2025-30355 can prevent a Synapse server from federating with other servers, disrupting communication.
Is there ongoing support for my version due to CVE-2025-30355?
Support for versions affected by CVE-2025-30355 is limited, and upgrading is strongly recommended to ensure security.
- agent/weakness
- agent/title
- agent/type
- agent/first-publish-date
- agent/severity
- agent/author
- collector/nvd-api
- source/NVD
- collector/nvd-cve
- agent/last-modified-date
- agent/description
- agent/references
- agent/source
- agent/guess-ai
- agent/software-canonical-lookup
- agent/software-canonical-lookup-request
- agent/softwarecombine
- collector/github-advisory-latest
- source/GitHub
- alias/GHSA-v56r-hwv5-mxg6
- alias/CVE-2025-30355
- agent/tags
- collector/mitre-cve
- source/MITRE
- agent/event
- collector/epss-latest
- source/FIRST
- agent/epss
- collector/github-advisory
- vendor/synapse
- canonical/synapse
- package-manager/pip