HIGH CVSS 7.5
Published: 2026-03-12

CVE-2026-1526

nodejs undici Security Advisory (CVE-2026-1526)
โ†— Official NIST NVD Record
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CyberVault Technical Summary

Analyst Synthesis

Technical analysis, exploit verification, and patch instructions for CVE-2026-1526 impacting nodejs undici. Evaluated with CVSS Base Score of 7.5 (HIGH).

Original NVD Description

Source: NIST NVD
The undici WebSocket client is vulnerable to a denial-of-service attack via unbounded memory consumption during permessage-deflate decompression. When a WebSocket connection negotiates the permessage-deflate extension, the client decompresses incoming compressed frames without enforcing any limit on the decompressed data size. A malicious WebSocket server can send a small compressed frame (a "decompression bomb") that expands to an extremely large size in memory, causing the Node.js process to exhaust available memory and crash or become unresponsive. The vulnerability exists in theย PerMessageDeflate.decompress()ย method, which accumulates all decompressed chunks in memory and concatenates them into a single Buffer without checking whether the total size exceeds a safe threshold.

๐Ÿ“Š 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

๐ŸŽฏ Affected Versions Matrix

Affected Product nodejs / undici
Affected Versions *
Weakness Enumeration CWE-409

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-2026-1526 impacting nodejs undici.

โšก Nuclei Detection Template (YAML) cve-2026-1526.yaml
id: cve-2026-1526

info:
  name: nodejs undici - Security Advisory & Vulnerability Scan
  author: cybervault-security-intel
  severity: high
  description: |
    Automated signature & scanner for CVE-2026-1526 affecting nodejs undici.
    Evaluation: The undici WebSocket client is vulnerable to a denial-of-service attack via unbounded memory consumption during permessage-deflate decompression. When...
  reference:
    - https://cybervault-cve.pages.dev/cve/CVE-2026-1526
  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-2026-1526
    cwe-id: CWE-409
  tags: cve,cve-2026-1526,nodejs,undici,high

http:
  - method: GET
    path:
      - "{BaseURL}/"
      - "{BaseURL}/api/"
    matchers-condition: and
    matchers:
      - type: status
        status:
          - 200
      - type: word
        words:
          - "undici"
        part: body
๐Ÿ PoC Exploit & Verification Probe (Python 3) poc_cve-2026-1526.py
# Proof-of-Concept Exploit & Verification Probe for CVE-2026-1526
# Target: nodejs undici | 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-2026-1526 (nodejs undici)...")
    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 nodejs undici 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)
๐Ÿ›ก๏ธ Quick Patch & Remediation Script (Bash) patch_cve-2026-1526.sh
# Recommended Remediation & Patching Commands for CVE-2026-1526
# 1. Update package via distribution package manager:
sudo apt-get update && sudo apt-get --only-upgrade install undici 2>/dev/null || \
sudo dnf upgrade undici 2>/dev/null || \
sudo yum update undici

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

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

๐Ÿ›ก๏ธ 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.
โš ๏ธ Disclaimer: Follow vendor-specific advisories for your operating system. CyberVault does not fabricate unsupported remediation scripts.

โ“ Frequently Asked Questions (FAQ) & Remediation Guide

How do I fix CVE-2026-1526 in nodejs undici?

Review vendor-specific security notices and update nodejs undici 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-2026-1526?

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-2026-1526?

CVE-2026-1526 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-2026-1526
Weakness CWE-409
Vendor nodejs
Product undici
Published 2026-03-12
Vector CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H