CVE-2021-39906

Severity: medium (CVSS 6.1 v3.1)
Exploited in the wild: not listed in CISA KEV
EPSS: 60.7% probability of exploitation in the next 30 days
Public exploit or detection template: none known
Published: 2021-11-05 · updated 2026-06-17
Weakness: CWE-79

Description

Improper validation of ipynb files in GitLab CE/EE version 13.5 and above allows an attacker to execute arbitrary JavaScript code on the victim's behalf.

Affected products

GitLab: from 13.5.0 before 14.2.6; from 14.3.0 before 14.3.4; from 14.4.0 before 14.4.1 — fixed in 14.2.6, 14.3.4, 14.4.1

How to fix

Upgrade to a fixed version: GitLab 14.2.6, 14.3.4, 14.4.1. Check the vendor advisory for mitigations.

References

https://gitlab.com/gitlab-org/cves/-/blob/master/2021/CVE-2021-39906.json
https://gitlab.com/gitlab-org/gitlab/-/issues/341566
https://hackerone.com/reports/1347600
https://gitlab.com/gitlab-org/cves/-/blob/master/2021/CVE-2021-39906.json
https://gitlab.com/gitlab-org/gitlab/-/issues/341566
https://hackerone.com/reports/1347600

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