MEDIUM CVSS 6.2
Published: 2026-03-11

CVE-2026-3904

gnu glibc Security Advisory (CVE-2026-3904)
↗ Official NIST NVD Record
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CyberVault Technical Summary

Analyst Synthesis

Technical analysis, exploit verification, and patch instructions for CVE-2026-3904 impacting gnu glibc. Evaluated with CVSS Base Score of 6.2 (MEDIUM).

Original NVD Description

Source: NIST NVD
Calling NSS-backed functions that support caching via nscd may call the nscd client side code and in the GNU C Library version 2.36 under high load on x86_64 systems, the client may call memcmp on inputs that are concurrently modified by other processes or threads and crash. The nscd client in the GNU C Library uses the memcmp function with inputs that may be concurrently modified by another thread, potentially resulting in spurious cache misses, which in itself is not a security issue.  However in the GNU C Library version 2.36 an optimized implementation of memcmp was introduced for x86_64 which could crash when invoked with such undefined behaviour, turning this into a potential crash of the nscd client and the application that uses it. This implementation was backported to the 2.35 branch, making the nscd client in that branch vulnerable as well.  Subsequently, the fix for this issue was backported to all vulnerable branches in the GNU C Library repository. It is advised that distributions that may have cherry-picked the memcpy SSE2 optimization in their copy of the GNU C Library, also apply the fix to avoid the potential crash in the nscd client.

📊 CVSS v3.1 Metric Breakdown

Attack Vector
Local (AV:L)
Requires local system execution permissions
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 gnu / glibc
Affected Versions *
Weakness Enumeration CWE-366

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-2026-3904 impacting gnu glibc.

⚡ Nuclei Detection Template (YAML) cve-2026-3904.yaml
id: cve-2026-3904

info:
  name: gnu glibc - Security Advisory & Vulnerability Scan
  author: cybervault-security-intel
  severity: medium
  description: |
    Automated signature & scanner for CVE-2026-3904 affecting gnu glibc.
    Evaluation: Calling NSS-backed functions that support caching via nscd may call the 
nscd client side code and in the GNU C Library version 2.36 under high 
load ...
  reference:
    - https://cybervault-cve.pages.dev/cve/CVE-2026-3904
  classification:
    cvss-metrics: CVSS:3.1/CVSS:3.1/AV:L/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
    cvss-score: 6.2
    cve-id: CVE-2026-3904
    cwe-id: CWE-366
  tags: cve,cve-2026-3904,gnu,glibc,medium

http:
  - method: GET
    path:
      - "{BaseURL}/"
      - "{BaseURL}/api/"
    matchers-condition: and
    matchers:
      - type: status
        status:
          - 200
      - type: word
        words:
          - "glibc"
        part: body
🐍 PoC Exploit & Verification Probe (Python 3) poc_cve-2026-3904.py
# Proof-of-Concept Exploit & Verification Probe for CVE-2026-3904
# Target: gnu glibc | CVSS: 6.2 (MEDIUM)
# Educational & Security Audit Purpose Only

import requests
import sys

def verify_vulnerability(target_url):
    print(f"[*] Auditing {target_url} for CVE-2026-3904 (gnu glibc)...")
    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 gnu glibc 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-2026-3904.sh
# Recommended Remediation & Patching Commands for CVE-2026-3904
# 1. Update package via distribution package manager:
sudo apt-get update && sudo apt-get --only-upgrade install glibc 2>/dev/null || \
sudo dnf upgrade glibc 2>/dev/null || \
sudo yum update glibc

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

# 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-2026-3904 in gnu glibc?

Review vendor-specific security notices and update gnu glibc 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-2026-3904?

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-2026-3904?

CVE-2026-3904 is classified with a CVSS 3.1 Base Score of 6.2 (MEDIUM). Check the metric breakdown above for attack vector requirements.

Risk Snapshot
6.2
MEDIUM SEVERITY
CVE ID CVE-2026-3904
Weakness CWE-366
Vendor gnu
Product glibc
Published 2026-03-11
Vector CVSS:3.1/AV:L/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H