// For flags

CVE-2025-30355

Synapse vulnerable to federation denial of service via malformed events

Severity Score

7.1
*CVSS v3.1

Exploit Likelihood

*EPSS

Affected Versions

*CPE

Public Exploits

1
*Multiple Sources

Exploited in Wild

-
*KEV

Decision

Track
*SSVC
Descriptions

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.

*Credits: N/A
CVSS Scores
Attack Vector
Network
Attack Complexity
Low
Privileges Required
Low
User Interaction
None
Scope
Unchanged
Confidentiality
None
Integrity
Low
Availability
High
Attack Vector
Network
Attack Complexity
Low
Authentication
Single
Confidentiality
None
Integrity
Partial
Availability
Complete
* Common Vulnerability Scoring System
SSVC
  • Decision:Track
Exploitation
None
Automatable
No
Tech. Impact
Partial
* Organization's Worst-case Scenario
Timeline
  • 2025-03-21 CVE Reserved
  • 2025-03-27 CVE Published
  • 2025-03-27 CVE Updated
  • 2025-03-27 First Exploit
  • 2025-03-30 EPSS Updated
  • ---------- Exploited in Wild
  • ---------- KEV Due Date
CWE
  • CWE-20: Improper Input Validation
CAPEC
Affected Vendors, Products, and Versions
Vendor Product Version Other Status
Vendor Product Version Other Status <-- --> Vendor Product Version Other Status
Element-hq
Search vendor "Element-hq"
 Synapse
Search vendor "Element-hq" for product "Synapse"
 < 1.127.1
Search vendor "Element-hq" for product "Synapse" and version " < 1.127.1"
en
Affected