CVE-2026-73416: JupyterLab PyPI Extension Blocklist Package-name Canonicalization Vulnerability

{
  "schema_version" : "1.4.0",
  "id" : "GHSA-89vp-jrxv-24w8",
  "modified" : "2026-08-12T19:56:08Z",
  "published" : "2026-07-22T23:14:27Z",
  "aliases" : [ "CVE-2026-73416" ],
  "summary" : "JupyterLab: PyPI extension blocklist package-name canonicalization bypass",
  "details" : "JupyterLab's PyPI extension manager enforces `blocked_extensions_uris` by comparing the requested install name to blocklist entries with a custom string normalization that is weaker than PyPI package-name canonicalization. An authenticated user can request a PyPI-equivalent spelling such as `JupyterLab.Git` for a blocklisted package such as `jupyterlab-git`; JupyterLab accepts the install request even though pip resolves the variant to the same package.\n\nThis has security implications only for deployments that combine all of the following:\n- an allowlist/blocklist configured with the intent of restricting which packages users can install;\n- the (default) PyPI Extension Manager enabled; and\n- kernels and terminals disabled or delegated to remote hosts (otherwise a user with kernel access can install packages directly regardless of this check) \n\n### Impact\n\nThe vulnerability lets an authenticated user install a package the operator specifically intended to block, defeating the allowlist/blocklist control. Because extensions in principle allow for arbitrary code execution, this vulnerability enables untrusted users to impact the integrity and availability of the jupyter-server instance that was provisioned to them. The user already has access to their own single-user server's data, so installing an extension grants no new read access.\n\nIn particular, the integrity of data can be impacted, and any hardening or restrictions on permitted user actions (download/upload limits) within the single-user server can be circumvented. Availability impact on a JupyterHub deployment is limited: while a user can be expected to exhaust their own kernel pod's resources, this vulnerability makes it easier to also exhaust the single-user server resources or generate more requests to shared resources; where limits are absent, resource exhaustion could potentially degrade the wider deployment.\n\n### Patches\n\nJupyterLab [`v4.6.2`](https://github.com/jupyterlab/jupyterlab/releases/tag/v4.6.2) and [`v4.5.10`](https://github.com/jupyterlab/jupyterlab/releases/tag/v4.5.10) contain the patch.\n\nUsers of applications that depend on JupyterLab, such as Notebook v7+, should update `jupyterlab` package too.\n\n### Workarounds\n\nNo action is required for deployments that do not have a custom allow/block list configured. Deployments wanting to disable programmatic extension installation entirely can switch to the read-only extension manager:\n\n```bash\n--LabApp.extension_manager=readonly\n```\n\nor the following traitlet:\n\n```python\nc.LabApp.extension_manager = 'readonly'\n```\n\nYou can confirm that the read-only manager is in use from GUI:\n\n<img width=\"293\" height=\"293\" alt=\"image\" src=\"https://github.com/user-attachments/assets/8016c809-633e-4ed0-a5bc-6bc4793caa0f\" />",
  "severity" : [ {
    "type" : "CVSS_V4",
    "score" : "CVSS:4.0/AV:N/AC:L/AT:P/PR:L/UI:N/VC:L/VI:H/VA:L/SC:N/SI:N/SA:N"
  } ],
  "affected" : [ {
    "package" : {
      "ecosystem" : "PyPI",
      "name" : "jupyterlab"
    },
    "ranges" : [ {
      "type" : "ECOSYSTEM",
      "events" : [ {
        "introduced" : "4.6.0"
      }, {
        "fixed" : "4.6.2"
      } ]
    } ],
    "database_specific" : {
      "last_known_affected_version_range" : "<= 4.6.1"
    }
  }, {
    "package" : {
      "ecosystem" : "PyPI",
      "name" : "jupyterlab"
    },
    "ranges" : [ {
      "type" : "ECOSYSTEM",
      "events" : [ {
        "introduced" : "4.5.0"
      }, {
        "fixed" : "4.5.10"
      } ]
    } ],
    "database_specific" : {
      "last_known_affected_version_range" : "<= 4.5.9"
    }
  } ],
  "references" : [ {
    "type" : "WEB",
    "url" : "https://github.com/jupyterlab/jupyterlab/security/advisories/GHSA-89vp-jrxv-24w8"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/jupyterlab/jupyterlab/pull/19184"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/jupyterlab/jupyterlab/pull/19185"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/jupyterlab/jupyterlab/pull/19186"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/jupyterlab/jupyterlab/commit/be9303f5bcd5308eaeae953c5a3c903046682c2c"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/jupyterlab/jupyterlab/commit/f1beab4a2027af4719d6edc07d52d6cf5a39a432"
  }, {
    "type" : "PACKAGE",
    "url" : "https://github.com/jupyterlab/jupyterlab"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/jupyterlab/jupyterlab/releases/tag/v4.5.10"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/jupyterlab/jupyterlab/releases/tag/v4.6.2"
  } ],
  "database_specific" : {
    "cwe_ids" : [ "CWE-178", "CWE-180" ],
    "severity" : "MODERATE",
    "github_reviewed" : true,
    "github_reviewed_at" : "2026-07-22T23:14:27Z",
    "nvd_published_at" : null
  }
}