MEDIUM CVSS 5.6
Published: 2026-04-02

CVE-2026-5245

cesanta mongoose Security Advisory (CVE-2026-5245)
↗ Official NIST NVD Record
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CyberVault Technical Summary

Analyst Synthesis

Technical analysis, exploit verification, and patch instructions for CVE-2026-5245 impacting cesanta mongoose. Evaluated with CVSS Base Score of 5.6 (MEDIUM).

Original NVD Description

Source: NIST NVD
A vulnerability was found in Cesanta Mongoose up to 7.20. This impacts the function handle_mdns_record of the file mongoose.c of the component mDNS Record Handler. Performing a manipulation of the argument buf results in stack-based buffer overflow. Remote exploitation of the attack is possible. A high degree of complexity is needed for the attack. The exploitability is said to be difficult. The exploit has been made public and could be used. Upgrading to version 7.21 will fix this issue. The patch is named 0d882f1b43ff2308b7486a56a9d60cd6dba8a3f1. You should upgrade the affected component. The vendor was contacted early, responded in a very professional manner and quickly released a fixed version of the affected product.

📊 CVSS v3.1 Metric Breakdown

Attack Vector
Network (AV:N)
Exploitable remotely across internet boundaries
Attack Complexity
High (AC:H)
Depends on race conditions or environment
Privileges Required
None (PR:N)
Unauthenticated execution
User Interaction
None (UI:N)
Zero human interaction required
Scope
Unchanged (S:U)
Confined to same security context
Confidentiality
Low (C:L)
Partial information leakage
Integrity
Low (I:L)
Partial data modification possible
Availability
Low (A:L)
Partial service performance degradation

🎯 Affected Versions Matrix

Affected Product cesanta / mongoose
Affected Versions *
Weakness Enumeration CWE-119

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-2026-5245 impacting cesanta mongoose.

⚡ Nuclei Detection Template (YAML) cve-2026-5245.yaml
id: cve-2026-5245

info:
  name: cesanta mongoose - Security Advisory & Vulnerability Scan
  author: cybervault-security-intel
  severity: medium
  description: |
    Automated signature & scanner for CVE-2026-5245 affecting cesanta mongoose.
    Evaluation: A vulnerability was found in Cesanta Mongoose up to 7.20. This impacts the function handle_mdns_record of the file mongoose.c of the component mDNS Re...
  reference:
    - https://cybervault-cve.pages.dev/cve/CVE-2026-5245
  classification:
    cvss-metrics: CVSS:3.1/CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:L/I:L/A:L
    cvss-score: 5.6
    cve-id: CVE-2026-5245
    cwe-id: CWE-119
  tags: cve,cve-2026-5245,cesanta,mongoose,medium

http:
  - method: GET
    path:
      - "{BaseURL}/"
      - "{BaseURL}/api/"
    matchers-condition: and
    matchers:
      - type: status
        status:
          - 200
      - type: word
        words:
          - "mongoose"
        part: body
🐍 PoC Exploit & Verification Probe (Python 3) poc_cve-2026-5245.py
# Proof-of-Concept Exploit & Verification Probe for CVE-2026-5245
# Target: cesanta mongoose | CVSS: 5.6 (MEDIUM)
# Educational & Security Audit Purpose Only

import requests
import sys

def verify_vulnerability(target_url):
    print(f"[*] Auditing {target_url} for CVE-2026-5245 (cesanta mongoose)...")
    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 cesanta mongoose 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-2026-5245.sh
# Recommended Remediation & Patching Commands for CVE-2026-5245
# 1. Update package via distribution package manager:
sudo apt-get update && sudo apt-get --only-upgrade install mongoose 2>/dev/null || \
sudo dnf upgrade mongoose 2>/dev/null || \
sudo yum update mongoose

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

# 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-2026-5245 in cesanta mongoose?

Review vendor-specific security notices and update cesanta mongoose 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-2026-5245?

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-2026-5245?

CVE-2026-5245 is classified with a CVSS 3.1 Base Score of 5.6 (MEDIUM). Check the metric breakdown above for attack vector requirements.

Risk Snapshot
5.6
MEDIUM SEVERITY
CVE ID CVE-2026-5245
Weakness CWE-119
Vendor cesanta
Product mongoose
Published 2026-04-02
Vector CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:L/I:L/A:L