CVE-2026-86049Jupyter Server: 5xx request logging leaks token-bearing Referer header values
Updated under an hour ago ()
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No exploitation reported and no EPSS estimate yet.
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Jupyter Server is the backend for Jupyter web applications. Prior to version 2.21.0, the 5xx request logging path in jupyter_server/log.py copies the Referer header into a JSON header block without applying the token scrubbing used for the request URI. A request that returns HTTP 500 while the Referer contains a token-bearing URL can therefore write that token to server logs in plaintext. An attacker who can read those logs can recover the token and use the affected user's Jupyter Server permissions. This issue is fixed in version 2.21.0.
- CVSS
- 7.1 HIGH (v3.1, CNA)CVSS:3.1/AV:N/AC:H/PR:L/UI:R/S:U/C:H/I:H/A:H
- Weakness (CWE)
- CWE-532
- Known exploited
- Not in CISA's KEV catalog
- EPSS (exploitation in the next 30 days)
- Not loaded for this CVE
- Assigned by
- GitHub_M
- NVD analysis
- Awaiting Analysis
- Record last updated
- Sep 18, 2026
- First seen by InfoSec Signals
- Oct 9, 2026
Affected products
jupyter-server jupyter_server jupyter_server:jupyter_server (from the name) | before 2.21.0 | CNA record |
References
- https://github.com/jupyter-server/jupyter_server/security/advisories/GHSA-c3mw-737p-c7g2x-refsource-confirm
- https://github.com/jupyter-server/jupyter_server/pull/1681x-refsource-misc
- https://github.com/jupyter-server/jupyter_server/commit/52513529af7096e622c00911b17627b266294717x-refsource-misc
- https://github.com/jupyter-server/jupyter_server/releases/tag/v2.21.0x-refsource-misc
The CVE record on cve.org NVD's entry
The CVE record is authoritative. Products marked “from the name” were identified from the CNA's free-text names, not a CPE, and are matched less certainly. This product uses the NVD API but is not endorsed or certified by the NVD.