CVE-2026-40110

Summary

Jupyter Server is the backend for Jupyter web applications. In versions 2.17.0 and earlier, the Origin header validation uses Python's re.match() to check incoming origins against the allow_origin_pat configuration value. Because re.match() only anchors at the start of the string and does not require a full match, a pattern intended to match only a trusted domain (e.g., trusted.example.com) will also match any origin that begins with that domain followed by additional characters (e.g., trusted.example.com.evil.com). An attacker who controls such a domain can bypass the CORS origin restriction and make cross-origin requests to the Jupyter Server API from an untrusted site. This issue has been fixed in version 2.18.0.

Affected Software

Weaknesses

• CWE-777: CWE-777: Regular Expression without Anchors

ADP Enrichment

CISA ADP Vulnrichment

• SSVC:
• Exploitation: none
  • Automatable: no
  • Technical Impact: total

jupyter-server: Jupyter Server: Cross-Origin Resource Sharing (CORS) bypass via improper Origin header validation

Additional References

• https://access.redhat.com/security/cve/CVE-2026-40110
• https://bugzilla.redhat.com/show_bug.cgi?id=2466912
• https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-40110.json

References

• https://github.com/jupyter-server/jupyter_server/security/advisories/GHSA-24qx-w28j-9m6p
• https://github.com/jupyter-server/jupyter_server/pull/603
• https://github.com/jupyter-server/jupyter_server/commit/057869a327c46730afede3eab0ca2d2e3e74acea
• https://github.com/jupyter-server/jupyter_server/commit/49b34392feaa97735b3b777e3baf8f22f2a14ed8

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