MEDIUM CVSS 6.5
Published: 2026-03-16

CVE-2026-28490

authlib authlib Security Advisory (CVE-2026-28490)
↗ Official NIST NVD Record
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CyberVault Technical Summary

Analyst Synthesis

Technical analysis, exploit verification, and patch instructions for CVE-2026-28490 impacting authlib authlib. Evaluated with CVSS Base Score of 6.5 (MEDIUM).

Original NVD Description

Source: NIST NVD
Authlib is a Python library which builds OAuth and OpenID Connect servers. Prior to version 1.6.9, a cryptographic padding oracle vulnerability was identified in the Authlib Python library concerning the implementation of the JSON Web Encryption (JWE) RSA1_5 key management algorithm. Authlib registers RSA1_5 in its default algorithm registry without requiring explicit opt-in, and actively destroys the constant-time Bleichenbacher mitigation that the underlying cryptography library implements correctly. This issue has been patched in version 1.6.9.

📊 CVSS v3.1 Metric Breakdown

Attack Vector
Network (AV:N)
Exploitable remotely across internet boundaries
Attack Complexity
High (AC:H)
Depends on race conditions or environment
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
High (C:H)
Total information disclosure
Integrity
Low (I:L)
Partial data modification possible
Availability
None (A:N)
No system availability impact

🎯 Affected Versions Matrix

Affected Product authlib / authlib
Affected Versions *
Weakness Enumeration CWE-203

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-2026-28490 impacting authlib authlib.

⚡ Nuclei Detection Template (YAML) cve-2026-28490.yaml
id: cve-2026-28490

info:
  name: authlib authlib - Security Advisory & Vulnerability Scan
  author: cybervault-security-intel
  severity: medium
  description: |
    Automated signature & scanner for CVE-2026-28490 affecting authlib authlib.
    Evaluation: Authlib is a Python library which builds OAuth and OpenID Connect servers. Prior to version 1.6.9, a cryptographic padding oracle vulnerability was id...
  reference:
    - https://cybervault-cve.pages.dev/cve/CVE-2026-28490
  classification:
    cvss-metrics: CVSS:3.1/CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:L/A:N
    cvss-score: 6.5
    cve-id: CVE-2026-28490
    cwe-id: CWE-203
  tags: cve,cve-2026-28490,authlib,authlib,medium

http:
  - method: GET
    path:
      - "{BaseURL}/"
      - "{BaseURL}/api/"
    matchers-condition: and
    matchers:
      - type: status
        status:
          - 200
      - type: word
        words:
          - "authlib"
        part: body
🐍 PoC Exploit & Verification Probe (Python 3) poc_cve-2026-28490.py
# Proof-of-Concept Exploit & Verification Probe for CVE-2026-28490
# Target: authlib authlib | CVSS: 6.5 (MEDIUM)
# Educational & Security Audit Purpose Only

import requests
import sys

def verify_vulnerability(target_url):
    print(f"[*] Auditing {target_url} for CVE-2026-28490 (authlib authlib)...")
    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 authlib authlib 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-2026-28490.sh
# Recommended Remediation & Patching Commands for CVE-2026-28490
# 1. Update package via distribution package manager:
sudo apt-get update && sudo apt-get --only-upgrade install authlib 2>/dev/null || \
sudo dnf upgrade authlib 2>/dev/null || \
sudo yum update authlib

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

# 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

❓ Frequently Asked Questions (FAQ) & Remediation Guide

How do I fix CVE-2026-28490 in authlib authlib?

Review vendor-specific security notices and update authlib authlib 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-2026-28490?

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-2026-28490?

CVE-2026-28490 is classified with a CVSS 3.1 Base Score of 6.5 (MEDIUM). Check the metric breakdown above for attack vector requirements.

Risk Snapshot
6.5
MEDIUM SEVERITY
CVE ID CVE-2026-28490
Weakness CWE-203
Vendor authlib
Product authlib
Published 2026-03-16
Vector CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:L/A:N