CVE-2025-67726: Tornado · Quadratic DoS via Crafted Multipart Parameters
Affects jupyterlabSource GCVE Database
Not known to be exploited · CVSS 7.5 High : upgrade to 4.5.1 soon.
Data as of 30 Oct 2026, 08:59 UTC
- Patch
- Available – fixed in 4.5.1
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:HExploitation evidence
Disclosed: evidence found.
CVE published 12 Dec 2025
Detectable: no evidence on record.
No public nuclei template indexed
Weaponized: no evidence on record.
No public exploit code indexed in Metasploit or Exploit-DB
Exploited in the wildExploited: no evidence on record.
Not in CISA KEV and no source reports exploitation
Observed by OffSeq MirageSeen by Mirage: no evidence on record.
No attack traffic recorded by OffSeq Mirage sensors
A missing step is not evidence of safety. Sources: cve.org (opens in a new tab), the Metasploit, Exploit-DB and nuclei-templates index as of 29 Oct 2026.
What to do
Upgrade jupyterlab to 4.5.1.
Affected software
| Product | Affected | Fixed in |
|---|---|---|
Homebrewjupyterlabpkg:brew/jupyterlabOther threats | Affected
| Fixed in
|
Check your own hosts for these packages with threat-finder (opens in a new tab), our free open-source scanner.
AI-suggested
A patch is available in jupyterlab version 4.5.1 that fixes this vulnerability. Users should upgrade to version 4.5.1 or later to remediate the issue. No additional mitigation steps are indicated by the vendor advisory.
Description
A high-severity vulnerability in Tornado's httputil.py _parseparam function causes quadratic CPU usage when parsing crafted multipart/form-data parameters. This can lead to a denial of service by making the server unresponsive due to its single event loop design. Versions of jupyterlab from 1.2.0 up to but not including 4.5.1 are affected. The issue is fixed in version 4.5.1.
References
- github.com/tornadoweb/tornado/security/advisories/GHSA-jhmp-mqwm-3gq8 (opens in a new tab)
- nvd.nist.gov/vuln/detail/CVE-2025-67726 (opens in a new tab)
- github.com/tornadoweb/tornado/commit/771472cfdaeebc0d89a9cc46e249f8891a6b29cd (opens in a new tab)
- github.com/pypa/advisory-database/tree/main/vulns/tornado/PYSEC-2025-267.yaml (opens in a new tab)
- github.com/tornadoweb/tornado (opens in a new tab)
- github.com/tornadoweb/tornado/releases/tag/v6.5.3 (opens in a new tab)