How severe is CVE-2026-5422?

CVE-2026-5422 has a CVSS 3.x base score of 8.1, rated high severity. It is exploitable over network with low attack complexity, requires low privileges and no user interaction. Impact on confidentiality is high, integrity high, and availability none.

Is CVE-2026-5422 being actively exploited?

It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 0% (35th percentile), an estimate of the probability of exploitation in the next 30 days.

What products are affected by CVE-2026-5422?

CVE-2026-5422 affects Jupyter Jupyter Server. See the affected-products list for the exact vulnerable versions.

How do I fix CVE-2026-5422?

Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround. Given its high severity, prioritise patching exposed systems.

Does CVE-2026-5422 have an EU (EUVD) identifier?

Yes. CVE-2026-5422 is tracked in the ENISA EU Vulnerability Database (EUVD) as EUVD-2026-33905.

When was CVE-2026-5422 published?

CVE-2026-5422 was published on 2026-06-02 and last updated on 2026-06-17.

CVE-2026-5422

CVE-2026-5422 is a high-severity vulnerability in Jupyter Jupyter Server with a CVSS 3.x base score of 8.1. It is not currently listed as actively exploited by CISA, and its EPSS exploit-prediction score is low. The underlying weakness is classified as CWE-23.

Key facts

Severity: High (CVSS 3.x base score 8.1)
EPSS exploit prediction: 0% (35th percentile)
Actively exploited: Not listed in CISA KEV
EU (EUVD) id: EUVD-2026-33905
Weakness: CWE-23
Affected product: Jupyter Jupyter Server
Published: 2026-06-02
Last modified: 2026-06-17

Description

A path traversal vulnerability exists in jupyter-server version 2.17.0 due to an incorrect root directory boundary check in the _get_os_path() function within jupyter_server/services/contents/fileio.py. The check uses startswith(root) without appending a trailing path separator, allowing sibling directories with names starting with the same prefix as root_dir to bypass the check. Additionally, the to_os_path() function in utils.py does not strip ".." from path parts, enabling traversal sequences to bypass the vulnerable check. This vulnerability can lead to unauthorized read/write access to files in sibling directories, potentially exposing sensitive data in shared hosting environments.

Frequently asked questions

What is CVE-2026-5422?: A path traversal vulnerability exists in jupyter-server version 2.17.0 due to an incorrect root directory boundary check in the _get_os_path() function within jupyter_server/services/contents/fileio.py. The check uses startswith(root) without appending a trailing path separator, allowing sibling directories with names starting with the same prefix as root_dir to bypass the check. Additionally, the to_os_path() function in utils.py does not strip ".." from path parts, enabling traversal sequences to bypass the vulnerable check. This vulnerability can lead to unauthorized read/write access to files in sibling directories, potentially exposing sensitive data in shared hosting environments.
How severe is CVE-2026-5422?: CVE-2026-5422 has a CVSS 3.x base score of 8.1, rated high severity. It is exploitable over network with low attack complexity, requires low privileges and no user interaction. Impact on confidentiality is high, integrity high, and availability none.
Is CVE-2026-5422 being actively exploited?: It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 0% (35th percentile), an estimate of the probability of exploitation in the next 30 days.
What products are affected by CVE-2026-5422?: CVE-2026-5422 affects Jupyter Jupyter Server. See the affected-products list for the exact vulnerable versions.
How do I fix CVE-2026-5422?: Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround. Given its high severity, prioritise patching exposed systems.
Does CVE-2026-5422 have an EU (EUVD) identifier?: Yes. CVE-2026-5422 is tracked in the ENISA EU Vulnerability Database (EUVD) as EUVD-2026-33905.
When was CVE-2026-5422 published?: CVE-2026-5422 was published on 2026-06-02 and last updated on 2026-06-17.

References

https://huntr.com/bounties/24a36953-6490-466f-8cb2-a90d1ca56e0f

Affected products (1)

cpe:2.3:a:jupyter:jupyter_server:2.17.0:*:*:*:*:*:*:*

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Threat intelligence

Threat-intel indicators referencing this CVE:

129.212.181.245 (ipv4-addr)