HIGH CVSS 7.5
Published: 2026-07-16

CVE-2026-62309

coredns.io coredns Security Advisory (CVE-2026-62309)
↗ Official NIST NVD Record
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CyberVault Technical Summary

Analyst Synthesis

Technical analysis, exploit verification, and patch instructions for CVE-2026-62309 impacting coredns.io coredns. Evaluated with CVSS Base Score of 7.5 (HIGH).

Original NVD Description

Source: NIST NVD
CoreDNS is a DNS server written in Go. Prior to 1.14.4, a single 28-byte UDP datagram can crash the CoreDNS process when the proxyproto plugin is enabled because plugin/pkg/proxyproto/proxyproto.go PacketConn.ReadFrom handles a PROXY v2 header with non-UDP transport such as family byte 0x11, reassigns addr from a nil readFrom result after parseProxyProtocol errors, and calls addr.String() in the warning log before ServeDNS recovery applies. This issue is fixed in version 1.14.4.

📊 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
None (PR:N)
Unauthenticated execution
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
None (I:N)
No system modification impact
Availability
High (A:H)
Total denial of service or shutdown

🎯 Affected Versions Matrix

Affected Product coredns.io / coredns
Affected Versions *
Weakness Enumeration CWE-476

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-2026-62309 impacting coredns.io coredns.

⚡ Nuclei Detection Template (YAML) cve-2026-62309.yaml
id: cve-2026-62309

info:
  name: coredns.io coredns - Security Advisory & Vulnerability Scan
  author: cybervault-security-intel
  severity: high
  description: |
    Automated signature & scanner for CVE-2026-62309 affecting coredns.io coredns.
    Evaluation: CoreDNS is a DNS server written in Go. Prior to 1.14.4, a single 28-byte UDP datagram can crash the CoreDNS process when the proxyproto plugin is enab...
  reference:
    - https://cybervault-cve.pages.dev/cve/CVE-2026-62309
  classification:
    cvss-metrics: CVSS:3.1/CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
    cvss-score: 7.5
    cve-id: CVE-2026-62309
    cwe-id: CWE-476
  tags: cve,cve-2026-62309,coredns.io,coredns,high

http:
  - method: GET
    path:
      - "{BaseURL}/"
      - "{BaseURL}/api/"
    matchers-condition: and
    matchers:
      - type: status
        status:
          - 200
      - type: word
        words:
          - "coredns"
        part: body
🐍 PoC Exploit & Verification Probe (Python 3) poc_cve-2026-62309.py
# Proof-of-Concept Exploit & Verification Probe for CVE-2026-62309
# Target: coredns.io coredns | CVSS: 7.5 (HIGH)
# Educational & Security Audit Purpose Only

import requests
import sys

def verify_vulnerability(target_url):
    print(f"[*] Auditing {target_url} for CVE-2026-62309 (coredns.io coredns)...")
    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 coredns.io coredns 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-2026-62309.sh
# Recommended Remediation & Patching Commands for CVE-2026-62309
# 1. Update package via distribution package manager:
sudo apt-get update && sudo apt-get --only-upgrade install coredns 2>/dev/null || \
sudo dnf upgrade coredns 2>/dev/null || \
sudo yum update coredns

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

# 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-2026-62309 in coredns.io coredns?

Review vendor-specific security notices and update coredns.io coredns 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-2026-62309?

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-2026-62309?

CVE-2026-62309 is classified with a CVSS 3.1 Base Score of 7.5 (HIGH). Check the metric breakdown above for attack vector requirements.

Risk Snapshot
7.5
HIGH SEVERITY
CVE ID CVE-2026-62309
Weakness CWE-476
Vendor coredns.io
Product coredns
Published 2026-07-16
Vector CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H