CRITICAL CVSS 10.0
Published: 2026-05-20

CVE-2026-42960

nlnetlabs unbound Security Advisory (CVE-2026-42960)
↗ Official NIST NVD Record
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CyberVault Technical Summary

Analyst Synthesis

Technical analysis, exploit verification, and patch instructions for CVE-2026-42960 impacting nlnetlabs unbound. Evaluated with CVSS Base Score of 10.0 (CRITICAL).

Original NVD Description

Source: NIST NVD
NLnet Labs Unbound up to and including version 1.25.0 is vulnerable to poisoning via promiscuous records for the authority section. Promiscuous RRSets that complement DNS replies in the authority section can be used to trick Unbound to cache such records. If an adversary is able to attach such records in a reply (i.e., spoofed packet, fragmentation attack) he would be able to poison Unbound's cache. A malicious actor can exploit the possible poisonous effect by injecting RRSets other than NS that are also accompanied by address records in a reply, for example MX. This could be achieved by trying to spoof a reply packet or fragmentation attacks. Unbound would then accept the relative address records in the additional section and cache them if the authority RRSet has enough trust at this point, i.e., in-zone data for the delegation point. Unbound 1.25.1 contains a patch with a fix that disregards address records from the additional section if they are not explicitly relevant only to authority NS records, mitigating the possible poison effect. This is a complement fix to CVE-2025-11411.

📊 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
Changed (S:C)
Impacts components beyond caller authority
Confidentiality
None (C:N)
No data confidentiality impact
Integrity
High (I:H)
Total modification of target system
Availability
High (A:H)
Total denial of service or shutdown

🎯 Affected Versions Matrix

Affected Product nlnetlabs / unbound
Affected Versions *
Weakness Enumeration CWE-349

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-2026-42960 impacting nlnetlabs unbound.

⚡ Nuclei Detection Template (YAML) cve-2026-42960.yaml
id: cve-2026-42960

info:
  name: nlnetlabs unbound - Security Advisory & Vulnerability Scan
  author: cybervault-security-intel
  severity: critical
  description: |
    Automated signature & scanner for CVE-2026-42960 affecting nlnetlabs unbound.
    Evaluation: NLnet Labs Unbound up to and including version 1.25.0 is vulnerable to poisoning via promiscuous records for the authority section. Promiscuous RRSets...
  reference:
    - https://cybervault-cve.pages.dev/cve/CVE-2026-42960
  classification:
    cvss-metrics: CVSS:3.1/CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:N/I:H/A:H
    cvss-score: 10.0
    cve-id: CVE-2026-42960
    cwe-id: CWE-349
  tags: cve,cve-2026-42960,nlnetlabs,unbound,critical

http:
  - method: GET
    path:
      - "{BaseURL}/"
      - "{BaseURL}/api/"
    matchers-condition: and
    matchers:
      - type: status
        status:
          - 200
      - type: word
        words:
          - "unbound"
        part: body
🐍 PoC Exploit & Verification Probe (Python 3) poc_cve-2026-42960.py
# Proof-of-Concept Exploit & Verification Probe for CVE-2026-42960
# Target: nlnetlabs unbound | CVSS: 10.0 (CRITICAL)
# Educational & Security Audit Purpose Only

import requests
import sys

def verify_vulnerability(target_url):
    print(f"[*] Auditing {target_url} for CVE-2026-42960 (nlnetlabs unbound)...")
    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 nlnetlabs unbound 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-2026-42960.sh
# Recommended Remediation & Patching Commands for CVE-2026-42960
# 1. Update package via distribution package manager:
sudo apt-get update && sudo apt-get --only-upgrade install unbound 2>/dev/null || \
sudo dnf upgrade unbound 2>/dev/null || \
sudo yum update unbound

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

# 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.

🔗 Verified Technical References

Authorities
  • No records filed in this category.
Distributions
  • No records filed in this category.

❓ Frequently Asked Questions (FAQ) & Remediation Guide

How do I fix CVE-2026-42960 in nlnetlabs unbound?

Review vendor-specific security notices and update nlnetlabs unbound 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-2026-42960?

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-2026-42960?

CVE-2026-42960 is classified with a CVSS 3.1 Base Score of 10.0 (CRITICAL). Check the metric breakdown above for attack vector requirements.

Risk Snapshot
10.0
CRITICAL SEVERITY
CVE ID CVE-2026-42960
Weakness CWE-349
Vendor nlnetlabs
Product unbound
Published 2026-05-20
Vector CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:N/I:H/A:H