{"id":"CVE-2026-40110","aliases":["GHSA-24qx-w28j-9m6p","PYSEC-2026-2187"],"title":"Jupyter Server has a  CORS Origin Validation Bypass via `re.match()` in `allow_origin_pat`","summary":"Jupyter Server has a  CORS Origin Validation Bypass via `re.match()` in `allow_origin_pat`","severity":"high","vendor":"jupyter-server","product":"jupyter-server","ecosystem":"pip","affected":["jupyter-server < 2.18.0"],"patched":["jupyter-server 2.18.0"],"published":"2026-05-05","updated":"2026-09-10","sourceUpdated":"2026-09-10T03:50:45.011553229Z","source":"OSV","sourceUrl":"https://osv.dev/vulnerability/GHSA-24qx-w28j-9m6p","references":[{"url":"https://github.com/jupyter-server/jupyter_server/security/advisories/GHSA-24qx-w28j-9m6p"},{"url":"https://nvd.nist.gov/vuln/detail/CVE-2026-40110"},{"url":"https://github.com/jupyter-server/jupyter_server/pull/603"},{"url":"https://github.com/jupyter-server/jupyter_server/commit/057869a327c46730afede3eab0ca2d2e3e74acea"},{"url":"https://github.com/jupyter-server/jupyter_server/commit/49b34392feaa97735b3b777e3baf8f22f2a14ed8"},{"url":"https://access.redhat.com/errata/RHSA-2026:43038"},{"url":"https://access.redhat.com/security/cve/CVE-2026-40110"},{"url":"https://bugzilla.redhat.com/show_bug.cgi?id=2466912"},{"url":"https://github.com/jupyter-server/jupyter_server"},{"url":"https://github.com/pypa/advisory-database/tree/main/vulns/jupyter-server/PYSEC-2026-2187.yaml"},{"url":"https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-40110.json"}],"tags":["osv","pip"],"epss":0.0034,"epssPercentile":0.2763,"ingestedAt":"2026-07-13T18:57:51.087Z","slug":"CVE-2026-40110","body":"## Overview\n\nJupyter Server uses `re.match()` to validate the Origin header against the `allow_origin_pat` configuration.\n\nSince `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`.\n\n### Impact\n\n<=2.17.0\n\n### Patches\n\n057869a327c46730afede3eab0ca2d2e3e74acea, 49b34392feaa97735b3b777e3baf8f22f2a14ed8 \n\n### Workarounds\n\nWrap your `allow_origin_pat` value with `^` and `$`\n\n### References\n\nhttps://github.com/jupyter-server/jupyter_server/pull/603\nhttps://docs.python.org/3/library/re.html#re.fullmatch\nhttps://docs.python.org/3/library/re.html#re.match\n\n## Affected packages\n\n- `jupyter-server < 2.18.0`\n\n## Remediation\n\nUpgrade to a patched release:\n\n- `jupyter-server 2.18.0`","depth":"twilight","depthScore":41,"depthScoreParts":{"impact":41.3,"likelihood":0.1,"exploitation":0,"ransomware":0},"changes":[]}