# CVE-2026-34052: JupyterHub LTI Authenticator denial of service via unbounded memory growth

Source: https://junglewise.ai/threats/cve-2026-34052-jupyterhub-lti-authenticator-denial-of-service-via-unbounded  
Publisher: Junglewise Threat Intelligence, https://junglewise.ai/threats  
Published: 2026-04-03. Updated: 2026-07-25  
License: CC BY 4.0 with a link back

CVE-2026-34052 · Severity: medium · CVSS 5.9 · Published 2026-04-03

A vulnerability in the JupyterHub LTI Authenticator, a tool used to integrate JupyterHub with learning management systems, can allow an attacker to crash the server. By sending a large volume of specific requests, an attacker can exhaust the server's memory, leading to a denial of service. This disrupts access for all users and may require a manual restart of the service to restore operations.

Vendors: [Jupyter](https://junglewise.ai/threats/vendors/jupyter), [PyPI](https://junglewise.ai/threats/vendors/pypi).

## Quick answers

**Is CVE-2026-34052 exploited in the wild?** No. Junglewise Threat Intelligence has no report of CVE-2026-34052 being exploited in the wild.

**How severe is CVE-2026-34052?** Medium severity, with a CVSS score of 5.9, published 3 April 2026.

**Which products and versions are affected?** JupyterHub Ltiauthenticator < 1.6.3; jupyterhub-ltiauthenticator (PyPI) ECOSYSTEM:introduced=0,fixed=1.6.3.

**Is there a fix for CVE-2026-34052?** Yes. jupyterhub-ltiauthenticator (PyPI): upgrade to 1.6.3 or later. Junglewise finds every place you run it, drafts the upgrade and applies it once you approve.

**How is CVE-2026-34052 attacked?** It is attacked over the network, in a software library.

**Am I affected by CVE-2026-34052?** Check whether you run Jupyter Lti Jupyterhub Authenticator, JupyterHub Ltiauthenticator or jupyterhub-ltiauthenticator (PyPI) at an affected version. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.

## How to fix

- jupyterhub-ltiauthenticator (PyPI): upgrade to 1.6.3 or later

  ```sh
  pip install "jupyterhub-ltiauthenticator>=1.6.3"
  ```


## Technical details

The LTI 1.1 validator in JupyterHub's ltiauthenticator package fails to limit the growth of its OAuth nonce storage. Nonces are stored in a class-level dictionary before signature validation occurs. An attacker who knows a valid consumer key can exploit this by sending a high volume of requests with unique nonces. Because these nonces are never cleared and are recorded regardless of whether the request signature is eventually validated, the dictionary grows indefinitely until the host system runs out of memory (CWE-401, CWE-770). This results in a Denial of Service (DoS). The issue is fixed in version 1.6.3.

## Affected products

- JupyterHub ltiauthenticator < 1.6.3

## Identifiers

- CVE-2026-34052
- GHSA-8mxq-7xr7-2fxj
- PYSEC-2026-2533

## Timeline

- 2026-03-26: patched: Version 1.6.3 released
- 2026-04-02: advisory: GitHub Security Advisory published
- 2026-04-03: disclosed: CVE published to NVD

## References

- [https://github.com/jupyterhub/ltiauthenticator/releases/tag/1.6.3](https://github.com/jupyterhub/ltiauthenticator/releases/tag/1.6.3)
- [https://github.com/jupyterhub/ltiauthenticator/security/advisories/GHSA-8mxq-7xr7-2fxj](https://github.com/jupyterhub/ltiauthenticator/security/advisories/GHSA-8mxq-7xr7-2fxj)

## Related threats

- [JupyterHub LTI Authenticator JWT signature validation bypass](https://junglewise.ai/threats/cve-2023-25574-jupyterhub-lti-authenticator-jwt-signature-validation-bypass)