Authentication bypass via unverified JWT signatures
Published Sep 18, 2026 · Updated Sep 18, 2026
Authentication bypass in AxDSan Mnemosyne before 3.10.1 allows remote attackers to read and modify sync data via forged JWTs. The sync server's auth check base64-decodes JWT data and accepts it without validating the HMAC-SHA256 signature, including alg:none or wrong-key tokens. The sync endpoint must be network-reachable and configured for JWT authentication; successful forgery permits user impersonation, sync-state reads, and malicious state pushes.
Summary
What happened
Authentication bypass in AxDSan Mnemosyne before 3.10.1 allows remote attackers to read and modify sync data via forged JWTs. The sync server's auth check base64-decodes JWT data and accepts it without validating the HMAC-SHA256 signature, including alg:none or wrong-key tokens. The sync endpoint must be network-reachable and configured for JWT authentication; successful forgery permits user impersonation, sync-state reads, and malicious state pushes.
The record
- CVE
- CVE-2026-59163
- Published
- Sep 18, 2026
- Updated
- Sep 18, 2026
- Vendor
- AxDSan
- Product
- Mnemosyne
- Classifications
- T1550.001
- Attack vector
- network
- Privileges
- unauthenticated
Timeline
How it unfolded
- Sep 18, 2026CVE publishedPublication date reported by the CVE source.
- Sep 18, 2026Record updatedLatest update available in the CVE record.
Exploitability
Present is not the same as exploitable
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Is a vulnerable build present?
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- Affected versionversion=< 3.10.1
What conditions does exploitation require?
What is affected?
Published CVSS scores
CVSS describes severity. EPSS estimates exploitation probability.
Attacks
What attackers are doing with it
Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.
Activity data is delayed. The latest report is Sep 28, 2026.
Weakness, pattern, technique
Public exploit references
- Forged JWT sync-status reproductionproof of concept · demonstrated
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Technologies
Your stack
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Your stack
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