{"id":"CVE-2026-73416","aliases":[],"url":"https://o3.security/vulnerability/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\" />","published":"2026-07-22T23:14:27Z","modified":"2026-08-12T20:00:09.906926487Z","cvss":null,"epss":null,"cisaKev":null,"exploitsKnown":null,"affectedPackages":[{"ecosystem":"PyPI","name":"jupyterlab","fixedVersion":"4.6.2"},{"ecosystem":"PyPI","name":"jupyterlab","fixedVersion":"4.5.10"}],"fix":{"url":"https://github.com/jupyterlab/jupyterlab/pull/19184","label":"jupyterlab/jupyterlab#19184"},"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"}],"provenance":{"sources":["OSV.dev","FIRST.org (EPSS)"],"lastVerified":"2026-08-12T20:00:09.906926487Z"}}