CVE-2026-35397: Jupyter Server path traversal (CVSS 8.8)

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.

CVSS 3.1 breakdown

Attack vectorNetwork

Attack complexityLow

Privileges requiredLow

User interactionNone

ScopeUnchanged

ConfidentialityHigh

IntegrityHigh

AvailabilityHigh

CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H

Affected products

Jupyter Server< 2.18.0

Remediation

Fixed in

Jupyter Server≥ 2.18.0

Patch & vendor advisories

https://github.com/jupyter-server/jupyter_server/security/advisories/GHSA-5789-5fc7-67v3

References

Related CVEs

Recent high-severity vulnerabilities sharing a weakness type.

Frequently asked

Is CVE-2026-35397 being actively exploited?

CVE-2026-35397 is not in the CISA KEV catalog. A public exploit reference exists, so treat it as exploitable. Its EPSS exploit probability is 0.67%.

How severe is CVE-2026-35397?

CVE-2026-35397 has a CVSS 3.1 base score of 8.8, rated high. EPSS estimates a 0.67% probability of exploitation.

Which products are affected by CVE-2026-35397?

Affected products include Jupyter Server.

How do I fix CVE-2026-35397?

Upgrade affected software to a fixed version, for example Jupyter Server 2.18.0 or later, then confirm no affected versions remain in your inventory.

How Secuno handles this

Secuno correlates vulnerabilities like CVE-2026-35397 against the real software inventory on every managed device, every day. Rather than a static severity, each match is scored in context: exploit availability, EPSS, the asset's exposure, and business criticality decide where it lands in the queue. If an affected version is present anywhere across your portfolio, it surfaces automatically with a prioritised remediation path.

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