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

> Attackers can bypass authentication in Mnemosyne's sync server by submitting unsigned or incorrectly signed JWTs, gaining unauthorized access.

- **Severity:** Critical 9.1 (`CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N`)
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Over the internet
- **Victim action needed:** Not needed
- **Fix available:** Yes
- **Published:** 18 Sep 2026
- **Updated:** 18 Sep 2026
- **Also known as:** GHSA-xcw4-53cc-hv32, PYSEC-2026-4106

## What is CVE-2026-59163?

CVE-2026-59163 is a critical authentication bypass vulnerability in AxDSan mnemosyne, published on 18 Sep 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.

### Official description

Mnemosyne is a memory layer for artificial intelligence agents. Prior to v3.10.1, the auth check in mnemosyne/core/sync_server.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.

Weakness: CWE-347 (Improper Verification of Cryptographic Signature)

## Which versions are affected by CVE-2026-59163?

3 open source packages ship an affected version, including mnemosyne-memory.


| Package | Ecosystem | Affected | Fixed in |
| --- | --- | --- | --- |
| `mnemosyne-memory` | PyPI | All versions | 3.10.1 |
| `mnemosyne-memory` | PyPI | All versions | 3.10.1 |
| `mnemosyne-memory` | PyPI | All versions | 3.10.1 |

## How do I fix CVE-2026-59163?

Upgrade mnemosyne-memory to 3.10.1 or later.

## Is CVE-2026-59163 being exploited?

It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-59163 exists.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-59163 and fix it if it is affected.

What it is: CVE-2026-59163 is a critical authentication bypass vulnerability in AxDSan mnemosyne, published on 18 Sep 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.
Exploitation: It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-59163 exists.

Affected packages and fixed versions:
- mnemosyne-memory (PyPI): affected all versions; fixed in 3.10.1
- mnemosyne-memory (PyPI): affected all versions; fixed in 3.10.1
- mnemosyne-memory (PyPI): affected all versions; fixed in 3.10.1

Task:
1. Search the dependency manifests and lockfiles (for example package.json, package-lock.json, requirements.txt, poetry.lock, uv.lock, pom.xml, build.gradle, go.mod, Cargo.lock, Gemfile.lock) and any Dockerfiles for the affected packages, including transitive dependencies.
2. If an affected version is in use, upgrade it to the fixed version for its release line with the project's package manager, so the lockfile is regenerated. Prefer the smallest upgrade that fixes it.
3. If there is no fix, or the upgrade would break the build, do not guess: explain the risk and the safest workaround instead.
4. Run the tests and summarise what changed and why.
5. If nothing in the project is affected, say so and change nothing.

Reference: https://insights.sbomify.com/CVE-2026-59163/ (Markdown: https://insights.sbomify.com/CVE-2026-59163/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-59163
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-59163
- OSV: https://osv.dev/vulnerability/CVE-2026-59163

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From sbomify Insights: https://insights.sbomify.com/CVE-2026-59163/
Summaries are generated and may contain mistakes; the official description above is the record.