HIGH CVSS 7.5
Published: 2026-03-18

CVE-2026-27135

nghttp2 nghttp2 Security Advisory (CVE-2026-27135)
↗ Official NIST NVD Record
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CyberVault Technical Summary

Analyst Synthesis

Technical analysis, exploit verification, and patch instructions for CVE-2026-27135 impacting nghttp2 nghttp2. Evaluated with CVSS Base Score of 7.5 (HIGH).

Original NVD Description

Source: NIST NVD
nghttp2 is an implementation of the Hypertext Transfer Protocol version 2 in C. Prior to version 1.68.1, the nghttp2 library stops reading the incoming data when user facing public API `nghttp2_session_terminate_session` or `nghttp2_session_terminate_session2` is called by the application. They might be called internally by the library when it detects the situation that is subject to connection error. Due to the missing internal state validation, the library keeps reading the rest of the data after one of those APIs is called. Then receiving a malformed frame that causes FRAME_SIZE_ERROR causes assertion failure. nghttp2 v1.68.1 adds missing state validation to avoid assertion failure. 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
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 nghttp2 / nghttp2
Affected Versions *
Weakness Enumeration CWE-617

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-2026-27135 impacting nghttp2 nghttp2.

⚡ Nuclei Detection Template (YAML) cve-2026-27135.yaml
id: cve-2026-27135

info:
  name: nghttp2 nghttp2 - Security Advisory & Vulnerability Scan
  author: cybervault-security-intel
  severity: high
  description: |
    Automated signature & scanner for CVE-2026-27135 affecting nghttp2 nghttp2.
    Evaluation: nghttp2 is an implementation of the Hypertext Transfer Protocol version 2 in C. Prior to version 1.68.1, the nghttp2 library stops reading the incomin...
  reference:
    - https://cybervault-cve.pages.dev/cve/CVE-2026-27135
  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-2026-27135
    cwe-id: CWE-617
  tags: cve,cve-2026-27135,nghttp2,nghttp2,high

http:
  - method: GET
    path:
      - "{BaseURL}/"
      - "{BaseURL}/api/"
    matchers-condition: and
    matchers:
      - type: status
        status:
          - 200
      - type: word
        words:
          - "nghttp2"
        part: body
🐍 PoC Exploit & Verification Probe (Python 3) poc_cve-2026-27135.py
# Proof-of-Concept Exploit & Verification Probe for CVE-2026-27135
# Target: nghttp2 nghttp2 | 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-2026-27135 (nghttp2 nghttp2)...")
    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 nghttp2 nghttp2 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-2026-27135.sh
# Recommended Remediation & Patching Commands for CVE-2026-27135
# 1. Update package via distribution package manager:
sudo apt-get update && sudo apt-get --only-upgrade install nghttp2 2>/dev/null || \
sudo dnf upgrade nghttp2 2>/dev/null || \
sudo yum update nghttp2

# 2. Inspect installed package versions for vulnerable scope:
dpkg -l | grep -i nghttp2 2>/dev/null || rpm -qa | grep -i nghttp2

# 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-2026-27135 in nghttp2 nghttp2?

Review vendor-specific security notices and update nghttp2 nghttp2 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-2026-27135?

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-2026-27135?

CVE-2026-27135 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-2026-27135
Weakness CWE-617
Vendor nghttp2
Product nghttp2
Published 2026-03-18
Vector CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H