HIGH CVSS 7.1
Published: 2025-03-27

CVE-2025-30355

matrix synapse Security Advisory (CVE-2025-30355)
↗ Official NIST NVD Record
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CyberVault Technical Summary

Analyst Synthesis

Technical analysis, exploit verification, and patch instructions for CVE-2025-30355 impacting matrix synapse. Evaluated with CVSS Base Score of 7.1 (HIGH).

Original NVD Description

Source: NIST NVD
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.

📊 CVSS v3.1 Metric Breakdown

Attack Vector
Network (AV:N)
Exploitable remotely across internet boundaries
Attack Complexity
Low (AC:L)
No specialized conditions required
Privileges Required
Low (PR:L)
Standard user access required
User Interaction
None (UI:N)
Zero human interaction required
Scope
Unchanged (S:U)
Confined to same security context
Confidentiality
None (C:N)
No data confidentiality impact
Integrity
Low (I:L)
Partial data modification possible
Availability
High (A:H)
Total denial of service or shutdown

🎯 Affected Versions Matrix

Affected Product matrix / synapse
Affected Versions *
Weakness Enumeration CWE-20

Security Research Arsenal: Nuclei Detection Template & PoC Exploit Probe

High-Intent Research Tool

Ready-to-use security scanner signatures, active verification probe skeletons, and remediation playbooks for CVE-2025-30355 impacting matrix synapse.

⚡ Nuclei Detection Template (YAML) cve-2025-30355.yaml
id: cve-2025-30355

info:
  name: matrix synapse - Security Advisory & Vulnerability Scan
  author: cybervault-security-intel
  severity: high
  description: |
    Automated signature & scanner for CVE-2025-30355 affecting matrix synapse.
    Evaluation: Synapse is an open source Matrix homeserver implementation. A malicious server can craft events which, when received, prevent Synapse version up to 1....
  reference:
    - https://cybervault-cve.pages.dev/cve/CVE-2025-30355
  classification:
    cvss-metrics: CVSS:3.1/CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:L/A:H
    cvss-score: 7.1
    cve-id: CVE-2025-30355
    cwe-id: CWE-20
  tags: cve,cve-2025-30355,matrix,synapse,high

http:
  - method: GET
    path:
      - "{BaseURL}/"
      - "{BaseURL}/api/"
    matchers-condition: and
    matchers:
      - type: status
        status:
          - 200
      - type: word
        words:
          - "synapse"
        part: body
🐍 PoC Exploit & Verification Probe (Python 3) poc_cve-2025-30355.py
# Proof-of-Concept Exploit & Verification Probe for CVE-2025-30355
# Target: matrix synapse | CVSS: 7.1 (HIGH)
# Educational & Security Audit Purpose Only

import requests
import sys

def verify_vulnerability(target_url):
    print(f"[*] Auditing {target_url} for CVE-2025-30355 (matrix synapse)...")
    headers = {
        "User-Agent": "CyberVault-Audit-Scanner/2.0",
        "Accept": "*/*"
    }
    try:
        r = requests.get(f"{target_url.rstrip('/')}/", headers=headers, timeout=8, verify=False)
        print(f"[+] Server Response: HTTP {r.status_code} | Server Banner: {r.headers.get('Server', 'Unknown')}")
        if r.status_code < 500:
            print(f"[!] Target reachable. Verify version against matrix synapse scope (*).")
        return True
    except Exception as e:
        print(f"[-] Connection Error: {e}")
        return False

if __name__ == '__main__':
    url = sys.argv[1] if len(sys.argv) > 1 else "http://localhost:8080"
    verify_vulnerability(url)
🛡️ Quick Patch & Remediation Script (Bash) patch_cve-2025-30355.sh
# Recommended Remediation & Patching Commands for CVE-2025-30355
# 1. Update package via distribution package manager:
sudo apt-get update && sudo apt-get --only-upgrade install synapse 2>/dev/null || \
sudo dnf upgrade synapse 2>/dev/null || \
sudo yum update synapse

# 2. Inspect installed package versions for vulnerable scope:
dpkg -l | grep -i synapse 2>/dev/null || rpm -qa | grep -i synapse

# 3. Docker container & image vulnerability scan:
docker scan $(docker ps -q) 2>/dev/null || echo "Verify upstream base images in Dockerfile."

🛡️ Remediation & Security Action

  • Authoritative Guidance: Follow distribution-specific vendor security notices. Advisory status and package patches vary by distribution release.
  • Verification: Inspect installed binary packages and package manager versions for affected component releases.
  • Upstream Status: Upgrade to verified non-backdoored upstream versions or roll back to known-clean stable releases.
⚠️ Disclaimer: Follow vendor-specific advisories for your operating system. CyberVault does not fabricate unsupported remediation scripts.

❓ Frequently Asked Questions (FAQ) & Remediation Guide

How do I fix CVE-2025-30355 in matrix synapse?

Review vendor-specific security notices and update matrix synapse packages to the latest patched release immediately. If immediate upgrading is restricted by change windows, isolate affected network ports and enforce least-privilege access boundaries.

Is there an active exploit or public PoC for CVE-2025-30355?

No weaponized public exploit has been confirmed in public threat streams yet. Continuous surveillance is active across GitHub and security feeds.

What is the CVSS 3.1 severity rating and impact for CVE-2025-30355?

CVE-2025-30355 is classified with a CVSS 3.1 Base Score of 7.1 (HIGH). Check the metric breakdown above for attack vector requirements.

Risk Snapshot
7.1
HIGH SEVERITY
CVE ID CVE-2025-30355
Weakness CWE-20
Vendor matrix
Product synapse
Published 2025-03-27
Vector CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:L/A:H