Vulnerability · Published May 5, 2026 · Assigned by GitHub_M
CVE-2026-35397jupyter-server path traversal allows access to sibling directories sharing root_dir name prefix
High 7.1
In plain English
A high-severity path traversal in jupyter_server from jupyter-server. Proof-of-concept exploit code is public. The chance it is exploited in the next 30 days is estimated at 0.6% (higher than 50% of all known vulnerabilities). Ready-made attack tooling exists: public proof-of-concept code. Fixed versions are available - upgrade the affected package.
Official 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.
Affected packages & fixed versions
| Ecosystem | Package | Fixed in | Advisory |
|---|---|---|---|
| Alpine:v3.24 | jupyter-server | 2.18.2-r0 | ALPINE-CVE-2026-35397 |
| Debian:12 | jupyter-server | no fix listed | DEBIAN-CVE-2026-35397 |
| Debian:13 | jupyter-server | no fix listed | DEBIAN-CVE-2026-35397 |
| Debian:14 | jupyter-server | 2.20.0-1 | DEBIAN-CVE-2026-35397 |
| PyPI | jupyter-server | 2.18.0 | PYSEC-2026-68 |
| PyPI | jupyter-server | 2.18.0 | GHSA-5789-5fc7-67v3 |
| Ubuntu:22.04:LTS | jupyter-server | no fix listed | UBUNTU-CVE-2026-35397 |
| Ubuntu:24.04:LTS | jupyter-server | no fix listed | UBUNTU-CVE-2026-35397 |
| Ubuntu:25.10 | jupyter-server | no fix listed | UBUNTU-CVE-2026-35397 |
| Ubuntu:26.04:LTS | jupyter-server | no fix listed | UBUNTU-CVE-2026-35397 |
| Ubuntu:26.10 | jupyter-server | no fix listed | UBUNTU-CVE-2026-35397 |
Affected products (as reported)
| Vendor | Product | Versions |
|---|---|---|
| jupyter-server | jupyter_server | < 2.18.0 |
Weakness: CWE-22 · Vector: CVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:U/C:H/I:H/A:L
References
- https://github.com/jupyter-server/jupyter_server/security/advisories/GHSA-5789-5fc7-67v3 x_refsource_CONFIRM
- https://access.redhat.com/security/cve/CVE-2026-35397 vdb-entry, x_refsource_REDHAT
- RHBZ#2466858 issue-tracking, x_refsource_REDHAT
- https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-35397.json x_sadp-csaf-vex
- https://access.redhat.com/errata/RHSA-2026:43038 vendor-advisory, x_refsource_REDHAT
- https://access.redhat.com/errata/RHSA-2026:60520 vendor-advisory, x_refsource_REDHAT