CVE-2026-40110: Jupyter server Jupyter Server Has A CORS Vulnerability

HIGH
Advisory Identifier: GHSA-24qx-w28j-9m6p
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CWE-625 CWE-777
Published
Advisory Summary

CVE-2026-40110 is a HIGH jupyter server has a cors vulnerability (CWE-625: Permissive Regular Expression) affecting Jupyter server libraries in the PyPI ecosystem. The issue involves jupyter server has a cors origin validation bypass via `re.match()` in `allow_origin_pat`. Remediation is available by upgrading affected packages to version 2.18.0.

CVE-2026-40110 at a Glance

CVE Identifier CVE-2026-40110
GHSA Identifier GHSA-24qx-w28j-9m6p
Severity HIGH
CVSS v3.1 Base Score N/A
CWE Classification CWE-625: Permissive Regular Expression
Affected Product Jupyter server
Package Ecosystem PyPI
Published Date
Last Updated

How to Fix CVE-2026-40110

To remediate this vulnerability, upgrade all affected Jupyter server dependencies to a patched release. Both direct and transitive dependencies should be checked, as frameworks or security libraries may pull in vulnerable versions transitively.

jupyter-server fixed: 2.18.0 
pip install jupyter-server>=2.18.0
Verify Direct and Transitive Dependencies

Run the following command in your project directory to verify that all resolved dependencies use the patched release: 

pip show jupyter-server

How to Check if You Are Affected

To determine whether your Python environment is affected by CVE-2026-40110, inspect your installed packages using pip:

pip show jupyter-server

Analyze the terminal output to locate any version of Jupyter server in your dependency tree. If any resolved version matches the vulnerable ranges listed in the table below (for example, versions earlier than 2.18.0), your application is affected.

Note: The pip show jupyter-server command checks currently installed packages in your active Python environment.

Technical Details

Vulnerability Mechanism & Technical Analysis

This vulnerability is classified under CWE-625: Permissive Regular Expression, where the product uses a regular expression that does not sufficiently restrict the set of allowed values. In Jupyter server, software state validation or input boundaries are circumvented during processing. Review the official source advisory statement below for specific affected components, classes, and reproduction details.

Source Advisory Statement

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

CVE-2026-40110 Affected Jupyter server Versions

1 component(s)
Fixed Versions:
2.18.0
Product / Package Ecosystem Affected Versions Fixed Version
jupyter-server
pypi/jupyter-server
PyPI
< 2.18.0
2.18.0

References

GitHub Advisory / Wiki ADVISORY
https://github.com/jupyter-server/jupyter_server/security/advisories/GHSA-24qx-w28j-9m6p
NVD — CVE-2026-40110 NVD
https://nvd.nist.gov/vuln/detail/CVE-2026-40110
Jupyter server Source Repository REPOSITORY
https://github.com/jupyter-server/jupyter_server/pull/603
Security Fix Commit FIX COMMIT
https://github.com/jupyter-server/jupyter_server/commit/057869a327c46730afede3eab0ca2d2e3e74acea
Security Fix Commit FIX COMMIT
https://github.com/jupyter-server/jupyter_server/commit/49b34392feaa97735b3b777e3baf8f22f2a14ed8
access.redhat.com/errata/rhsa-2026:43... WEB
https://access.redhat.com/errata/RHSA-2026:43038
Jupyter server Security Information SECURITY
https://access.redhat.com/security/cve/CVE-2026-40110
bugzilla.redhat.com/show_bug.cgi WEB
https://bugzilla.redhat.com/show_bug.cgi?id=2466912
Jupyter server Source Repository REPOSITORY
https://github.com/jupyter-server/jupyter_server
Jupyter server Source Repository REPOSITORY
https://github.com/pypa/advisory-database/tree/main/vulns/jupyter-server/PYSEC-2026-2187.yaml
Jupyter server Security Information SECURITY
https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-40110.json

Frequently Asked Questions

What is CVE-2026-40110?
CVE-2026-40110 is a security vulnerability in Jupyter server involving Jupyter Server has a CORS Origin Validation Bypass via `re.match()` in `allow_origin_pat` under CWE-625: Permissive Regular Expression.
Which Jupyter server versions are affected?
Affected versions include releases prior to 2.18.0 across affected packages: jupyter-server.
What version fixes CVE-2026-40110?
Upgrading to 2.18.0 (or the latest patched release for your respective branch) resolves the vulnerability.
Is jupyter-server affected?
Yes, jupyter-server is affected in releases prior to 2.18.0. Upgrade your dependency to 2.18.0 or later.
What CWE is associated with CVE-2026-40110?
CVE-2026-40110 is classified under CWE-625: Permissive Regular Expression (The product uses a regular expression that does not sufficiently restrict the set of allowed values.).
How can I check PyPI dependencies for CVE-2026-40110?
Run the dependency tree command: 'pip show jupyter-server'. This command lists direct and transitive dependencies in your build configuration so you can verify if a vulnerable version is resolved.
Machine-readable OSV JSON OSV v1.5 Schema
Normalized schema output
View Raw JSON 
{
  "schema_version" : "1.4.0",
  "id" : "GHSA-24qx-w28j-9m6p",
  "modified" : "2026-07-31T20:27:11Z",
  "published" : "2026-05-05T16:54:31Z",
  "aliases" : [ "CVE-2026-40110" ],
  "summary" : "Jupyter Server has a  CORS Origin Validation Bypass via `re.match()` in `allow_origin_pat`",
  "details" : "Jupyter 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",
  "severity" : [ {
    "type" : "CVSS_V4",
    "score" : "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"
  } ],
  "affected" : [ {
    "package" : {
      "ecosystem" : "PyPI",
      "name" : "jupyter-server"
    },
    "ranges" : [ {
      "type" : "ECOSYSTEM",
      "events" : [ {
        "introduced" : "0"
      }, {
        "fixed" : "2.18.0"
      } ]
    } ],
    "database_specific" : {
      "last_known_affected_version_range" : "<= 2.17.0"
    }
  } ],
  "references" : [ {
    "type" : "WEB",
    "url" : "https://github.com/jupyter-server/jupyter_server/security/advisories/GHSA-24qx-w28j-9m6p"
  }, {
    "type" : "ADVISORY",
    "url" : "https://nvd.nist.gov/vuln/detail/CVE-2026-40110"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/jupyter-server/jupyter_server/pull/603"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/jupyter-server/jupyter_server/commit/057869a327c46730afede3eab0ca2d2e3e74acea"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/jupyter-server/jupyter_server/commit/49b34392feaa97735b3b777e3baf8f22f2a14ed8"
  }, {
    "type" : "WEB",
    "url" : "https://access.redhat.com/errata/RHSA-2026:43038"
  }, {
    "type" : "WEB",
    "url" : "https://access.redhat.com/security/cve/CVE-2026-40110"
  }, {
    "type" : "WEB",
    "url" : "https://bugzilla.redhat.com/show_bug.cgi?id=2466912"
  }, {
    "type" : "PACKAGE",
    "url" : "https://github.com/jupyter-server/jupyter_server"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/pypa/advisory-database/tree/main/vulns/jupyter-server/PYSEC-2026-2187.yaml"
  }, {
    "type" : "WEB",
    "url" : "https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-40110.json"
  } ],
  "database_specific" : {
    "cwe_ids" : [ "CWE-625", "CWE-777" ],
    "severity" : "HIGH",
    "github_reviewed" : true,
    "github_reviewed_at" : "2026-05-05T16:54:31Z",
    "nvd_published_at" : "2026-05-05T22:16:00Z"
  }
}