---
title: "CVE-2026-59163: Mnemosyne has JWT signature verification bypass sync server that allows authentication bypass"
url: https://erroneo.us/security/cve/CVE-2026-59163/
description: "CVE-2026-59163 (mnemosyne-memory (PyPI)): Mnemosyne is a memory layer for artificial intelligence agents. Prior to v3.10.1, the auth check in…"
type: vulnerability-record
section: "Security Digest"
date_published: 2026-09-18
date_modified: 2026-09-18
publisher: erroneo.us
author: erroneo.us Security Desk
cve: "CVE-2026-59163"
kev: false
cvss: 9.1
epss: 0.00325
license: All rights reserved. Quote with attribution and a link.
---

# CVE-2026-59163: Mnemosyne has JWT signature verification bypass sync server that allows authentication bypass

**Signal:** Critical and remotely reachable. No known exploitation yet, but it is network-reachable without credentials. (Computed from CISA KEV, EPSS and CVSS; not an editorial verdict.)

## Should you act?

- Not in CISA KEV , but CISA’s SSVC assessment records a public proof-of-concept, so attack code exists.
- EPSS 0.3% , percentile 24: FIRST’s model estimates a 0.3% chance of exploitation activity in the next 30 days, higher than 24% of all scored CVEs (low). EPSS is a probability, not a verdict.
- Remotely reachable with no login and no user interaction. If the vulnerable service is exposed to the internet, prioritize it.
- Only applies if your dependency tree includes mnemosyne-memory (PyPI) <= 3.10.0, fixed in 3.10.1 . Check your lockfile, including transitive dependencies.

## What it is

Mnemosyne is a memory layer for artificial intelligence agents. Prior to v3.10.1, the auth check in mnemosyne/core/syncserver.py parsed the JWT's header and payload using base64 decoding, then passed the token to a jwt library call with options that effectively disabled signature verification. The server accepted any well-formed token regardless of the signature, including tokens with alg: none and tokens signed with the wrong key. The fix in v3.10.1 replaces the broken decode with a from-scratch HS256 verifier using only the Python standard library. For users who cannot upgrade immediately, restrict network access to the sync server endpoint to trusted clients only. Firewall, reverse proxy with mTLS, or localhost bind with SSH tunnel are all viable. The vulnerability is not exploitable against an unreachable endpoint.

## Affected packages

- PyPI `mnemosyne-memory` <= 3.10.0 → fixed: 3.10.1

## Affected products (CVE record)

- AxDSan mnemosyne: < 3.10.1

## Severity

- GitHub_M CVSS 3.1: 9.1 `CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N`
- GitHub CVSS 3.1: 9.1 `CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N`

## Exploitation

- CISA KEV: not listed (no confirmed in-the-wild exploitation known to CISA).
- CISA SSVC assessment: exploitation poc , automatable yes , technical impact total .
- FIRST EPSS (model of 2026-10-21): 0.33% probability of exploitation activity in the next 30 days; percentile 24.

## Sources

- [GitHub Advisory GHSA-xcw4-53cc-hv32](https://github.com/advisories/GHSA-xcw4-53cc-hv32)
- [CVE.org record CVE-2026-59163](https://www.cve.org/CVERecord?id=CVE-2026-59163)
- [NVD entry CVE-2026-59163](https://nvd.nist.gov/vuln/detail/CVE-2026-59163)
- [github.com](https://github.com/mnemosyne-oss/mnemosyne/security/advisories/GHSA-xcw4-53cc-hv32)
- [github.com](https://github.com/mnemosyne-oss/mnemosyne/pull/373)
- [github.com](https://github.com/mnemosyne-oss/mnemosyne/commit/a0b6b8711a1a485304971710dc3571e29ff9dbeb)
- [github.com](https://github.com/mnemosyne-oss/mnemosyne/releases/tag/v3.10.1)
- [github.com](https://github.com/AxDSan/mnemosyne/security/advisories/GHSA-xcw4-53cc-hv32)

---
Source page: https://erroneo.us/security/cve/CVE-2026-59163/ · Security Digest: https://erroneo.us/security/ · More: https://erroneo.us/llms.txt