Описание
Jupyter Server: Path Traversal via incorrect startswith() root directory check allows access to sibling directories
Summary
Jupyter Server <=2.17.0 can access directories sibling to the root directory, if it starts with the root dir's name.
PoC
Minimal:
Full PoC by @stef41: https://gist.github.com/Yann-P/66d4982a965dee8fcb8dd89db29e7006
Impact
It is possible for an authenticated user to access content outside the server's root_dir in siblings directories sharing the same prefix as the root_dir. The attacker can escalate access, reading, writing, and deleting from sibling directories.
This can have a tangible impact for deployments using predictable naming scheme with multi-tenant server, for example user1, user2, user3, ..., user10 etc, as user1 could access and modify files of all user10 - user19 and higher.
In a hypothetical system where users can choose a name of their folder, an attacker could choose a single-letter username to gain access to a significant number of sibling directories.
Workarounds
Use folder names that do not overlap.
Acknowledgments
Thank you to @stef41 for providing a useful PoC.
Ссылки
- https://github.com/jupyter-server/jupyter_server/security/advisories/GHSA-5789-5fc7-67v3
- https://nvd.nist.gov/vuln/detail/CVE-2026-35397
- https://access.redhat.com/errata/RHSA-2026:43038
- https://access.redhat.com/security/cve/CVE-2026-35397
- https://bugzilla.redhat.com/show_bug.cgi?id=2466858
- https://github.com/pypa/advisory-database/tree/main/vulns/jupyter-server/PYSEC-2026-68.yaml
- https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-35397.json
Пакеты
jupyter-server
<= 2.17.0
2.18.0
Связанные уязвимости
Jupyter Server is the backend for Jupyter web applications. In versions 2.17.0 and earlier, a path traversal vulnerability in the REST API allows an authenticated user to escape the configured root_dir and access sibling directories whose names begin with the same prefix as the root_dir. For example, with a root_dir named "test", the API permits access to a sibling directory named "testtest" through a crafted request to the /api/contents endpoint using encoded path components. An attacker can read, write, and delete files in affected sibling directories. Multi-tenant deployments using predictable naming schemes are particularly at risk, as a user with a directory named "user1" could access directories for user10 through user19 and beyond. A user who can choose a single-character folder name could gain access to a significant number of sibling directories. Version 2.18.0 contains a fix. As a workaround, ensure folder names do not share a common prefix with any sibling directory.
Jupyter Server is the backend for Jupyter web applications. In versions 2.17.0 and earlier, a path traversal vulnerability in the REST API allows an authenticated user to escape the configured root_dir and access sibling directories whose names begin with the same prefix as the root_dir. For example, with a root_dir named "test", the API permits access to a sibling directory named "testtest" through a crafted request to the /api/contents endpoint using encoded path components. An attacker can read, write, and delete files in affected sibling directories. Multi-tenant deployments using predictable naming schemes are particularly at risk, as a user with a directory named "user1" could access directories for user10 through user19 and beyond. A user who can choose a single-character folder name could gain access to a significant number of sibling directories. Version 2.18.0 contains a fix. As a workaround, ensure folder names do not share a common prefix with any sibling directory.
Jupyter Server is the backend for Jupyter web applications. In versions 2.17.0 and earlier, a path traversal vulnerability in the REST API allows an authenticated user to escape the configured root_dir and access sibling directories whose names begin with the same prefix as the root_dir. For example, with a root_dir named "test", the API permits access to a sibling directory named "testtest" through a crafted request to the /api/contents endpoint using encoded path components. An attacker can read, write, and delete files in affected sibling directories. Multi-tenant deployments using predictable naming schemes are particularly at risk, as a user with a directory named "user1" could access directories for user10 through user19 and beyond. A user who can choose a single-character folder name could gain access to a significant number of sibling directories. Version 2.18.0 contains a fix. As a workaround, ensure folder names do not share a common prefix with any sibling directory.
Jupyter Server is the backend for Jupyter web applications. In version ...