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CVE-2026-59163: CVE-2026-59163: Critical JWT Authentication Bypass in Mnemosyne Sync Server

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CVE-2026-59163: Critical JWT Authentication Bypass in Mnemosyne Sync Server

Vulnerability ID: CVE-2026-59163
CVSS Score: 9.1
Published: 2026-09-18

CVE-2026-59163 is a critical authentication bypass vulnerability in the Mnemosyne sync server. In versions prior to v3.10.1, the server's authentication logic decoded incoming JSON Web Tokens (JWT) but completely skipped cryptographic signature verification. An unauthenticated remote attacker can exploit this vulnerability to bypass authentication, impersonate arbitrary users, read synchronized AI agent states, or write malicious database updates.

TL;DR

An authentication bypass vulnerability in the Mnemosyne sync server allows remote attackers to spoof JWTs and gain full unauthorized access by omitting signature verification.

⚠️ Exploit Status: POC

Technical Details

  • CWE ID: CWE-347
  • Attack Vector: Network (AV:N)
  • CVSS: 9.1 (Critical)
  • EPSS: Not Available
  • Impact: Full Authentication Bypass
  • Exploit Status: PoC (Trivial to exploit)
  • KEV Status: Not Listed

Affected Systems

  • Mnemosyne Sync Server
  • Mnemosyne: < 3.10.1 (Fixed in: 3.10.1)

Code Analysis

Commit: a0b6b87

Implement _validate_jwt to perform cryptographic signature and algorithm checks

Commit: 5576939

Release bump for version v3.10.1

Mitigation Strategies

  • Upgrade Mnemosyne to v3.10.1 or later
  • Enforce network-level access control
  • Bind the sync server to localhost
  • Deploy a reverse proxy with mTLS

Remediation Steps:

  1. Run 'pip install --upgrade mnemosyne-memory==3.10.1' to apply the official patch.
  2. Audit configuration files to ensure 'jwt_secret' is populated with a high-entropy string.
  3. Configure firewall rules to block untrusted incoming connections to the sync port.
  4. Implement NGINX/HAProxy reverse proxy to enforce network-level authentication.

References

Read the full report for CVE-2026-59163 on our website for more details including interactive diagrams and full exploit analysis.

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