CVE-2026-35397

01/Description

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.

02/Affected products

jupyter: jupyter server

03/References7

• github.com/jupyter-server/jupyter_server/security/advisories/GH… ExploitVendor Advisory
• github.com/jupyter-server/jupyter_server/security/advisories/GH… ExploitVendor Advisory
• access.redhat.com/errata/RHSA-2026:43038
• access.redhat.com/errata/RHSA-2026:60520
• access.redhat.com/security/cve/CVE-2026-35397
• bugzilla.redhat.com/show_bug.cgi?id=2466858
• security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-35397…