EUVD-2026-27510
GHSA-24qx-w28j-9m6p
CVSS VectorNVD
CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:P/VC:H/VI:H/VA:L/SC:L/SI:L/SA:L/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X
Lifecycle Timeline
4DescriptionNVD
Jupyter Server uses re.match() to validate the Origin header against the allow_origin_pat configuration.
Since re.match() only anchors at the start of the string, an attacker who controls a domain like http://trusted.example.com.evil.com/ passes validation against a pattern intended to match only trusted.example.com.
Impact
<=2.17.0
Patches
057869a327c46730afede3eab0ca2d2e3e74acea, 49b34392feaa97735b3b777e3baf8f22f2a14ed8
Workarounds
Wrap your allow_origin_pat value with ^ and $
References
https://github.com/jupyter-server/jupyter_server/pull/603 https://docs.python.org/3/library/re.html#re.fullmatch https://docs.python.org/3/library/re.html#re.match
AnalysisAI
Cross-Origin Resource Sharing (CORS) bypass in Jupyter Server <= 2.17.0 allows attackers controlling malicious subdomains to bypass origin validation and access sensitive notebook data. The vulnerability stems from incorrect use of Python's re.match() function in the allow_origin_pat configuration, which only anchors at the start of strings. …
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RemediationAI
Within 24 hours: Identify all Jupyter Server instances running version 2.17.0 or earlier in your environment using asset inventory and vulnerability scanning tools. Within 7 days: Upgrade all affected Jupyter Server instances to version 2.18.0 or later. …
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