JupyterHub has cross-origin form POSTs bypass XSRF (CWE-352)
Summary
JupyterHub's XSRF protection (updated in 4.1.0) inappropriately treated requests with Sec-Fetch-Mode: no-cors as same-origin requests, which they are not, bypassing XSRF checks. The JSON API is not affected, only HTTP form endpoints, such as /hub/spawn and /hub/accept-share, meaning attackers could trigger server spawn (but not access the server) and if the attacker is a JupyterHub user permitted to share access to their server, cause a user to accept a share and have access to the attacker's server.
Patches
Upgrade to JupyterHub 5.4.5.
Mitigations
If a reverse proxy is in use, drop requests to JupyterHub with Sec-Fetch-Mode: no-cors.
Affected software
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| Platform | Package | Vulnerable versions | Fixed in |
|---|---|---|---|
| Python (PyPI) | jupyterhub | >= 4.1.0, < 5.4.5 | 5.4.5 |
References
- CVSS vector
CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:L/A:L- Weakness (CWE)
CWE-352- Platform
- Python (PyPI)
- Package
jupyterhub- Disclosed
- 05.05.2026
- Updated
- 11.10.2026 15:17
Sources and licenses
OSV / GitHub Advisory Database - PYSEC-2026-2189 - PyPA Advisory Database; CC BY 4.0
OSV / GitHub Advisory Database - GHSA-m68r-v472-jgq9 - CC BY 4.0
Vulnerability history: jupyterhub
All published vulnerabilities of this package (Python (PyPI)), newest first. Shows whether this is a one-off slip or a package that needs watching.
- Total entries
- 8
- First → latest
- 04.2019 08.2026
- Without a fix
- 0
- Exploited in attacks
- 0
Severity breakdown
- High 2
- Medium 6
Disclosures per year
- 2019: 1
- 2020: 0
- 2021: 2
- 2022: 0
- 2023: 0
- 2024: 2
- 2025: 0
- 2026: 3
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JupyterHub has cross-origin form POSTs bypass XSRF (CWE-352) this entry
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