CVE-2021-39906
MediumImproper 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.
Published Nov 4, 2021 · Updated Sep 10, 2026 · Also known as BIT-gitlab-2021-39906, UBUNTU-CVE-2021-39906
Key Facts
Patch immediately- CVE-2021-39906 is a medium-severity vulnerability (CVSS 6.1 v3.1) affecting GitLab.
- It is not listed in any known-exploited vulnerabilities catalog. No public exploit code is known.
- EPSS estimates a 61% probability of exploitation in the next 30 days.
- Fixed versions are available, including GitLab 14.2.6, GitLab 14.3.4, GitLab 14.4.1.
- Brandefense priority: patch immediately, because it is very likely to be exploited soon.
CVSS v3.1
6.1
CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N
EPSS (30-day exploit likelihood)
61%
Higher than 99.1% of all scored CVEs
Exploited in the wild
No known
Not in a known-exploited catalog
Public exploit code
None known
Get the full CVE-2021-39906 brief as a PDF
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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
7 affected entries in total| Product | Affected versions | Fixed in |
|---|---|---|
| GitLabGitlab | >= 13.5.0, >= >=13.5, <14.2.6 | 14.2.6 |
Patched Releases
GitLab
14.2.6, 14.3.4, 14.4.1, 14.5.0-1, 15.10.8+ds1-2
Timeline
Publicly disclosed
Nov 4, 2021
Last updated
Sep 10, 2026
Weakness Type
- CWE-79 Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting')
References
- advisoryhttps://gitlab.com/gitlab-org/cves/-/blob/master/2021/CVE-2021-39906.json
- advisoryhttps://hackerone.com/reports/1347600
- advisoryhttps://ubuntu.com/security/CVE-2021-39906
- advisoryhttps://www.cve.org/CVERecord?id=CVE-2021-39906
- articlehttps://nvd.nist.gov/vuln/detail/CVE-2021-39906
FAQ
Common Questions.
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: GitLab versions >= 13.5.0, >= >=13.5, <14.2.6. The full list is in the CVE brief.
It is not listed in any known-exploited vulnerabilities catalog.
No, it is not currently listed in the CISA Known Exploited Vulnerabilities catalog.
No public exploit code is known.
Fixed versions are available, including GitLab 14.2.6, GitLab 14.3.4, GitLab 14.4.1.
Brandefense priority: patch immediately, because it is very likely to be exploited soon.
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