No exploitation reportedFix available

CVE-2021-39906

Q: Is CVE-2021-39906 actively exploited?

Active exploitation of CVE-2021-39906 has not been confirmed. Its EPSS score was 60.7% on 2026-10-22, the estimated probability of exploitation in the next 30 days.

Q: What is the CVSS score for CVE-2021-39906?

CVE-2021-39906 has a CVSS v3 base score of 6.1 (MEDIUM severity), with vector string CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N.

No exploitation reported by the sources we read.

Published2021-11-05
Fixed in14.4.1 · 14.3.4 · 14.2.6
WeaknessCWE-79

Am I affected?

With a domain, we read the version its public headers and pages expose. A distribution build can carry the fix under an older number.

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.

Timeline

dates in UTC

2021-11-0500:15CVE publishedNVD
2026-10-2319:23EPSS crossed 10 %FIRST EPSS

Observed activity

isMalicious corpus · updated 2026-10-23 18:48 UTC

Indicators tagged with this CVE, per day0 indicators over 7 days

Block these indicators

Firewall list (EDL, text): https://api.ismalicious.com/edl/cve/CVE-2021-39906?format=txt
CSV export: https://api.ismalicious.com/edl/cve/CVE-2021-39906?format=csv
TAXII collection of exploited CVEs
The EDL and CSV take an API key on the Pro plan.

Versions per branch

NVD

GitLab

Branch	Affected	Fixed in	Source
14.4	≥ 14.4.0, < 14.4.1	14.4.1	NVD
14.3	≥ 14.3.0, < 14.3.4	14.3.4	NVD
14.2	≥ 13.5.0, < 14.2.6	14.2.6	NVD

as publishedRanges as NVD and OSV publish them; a distribution’s build can be fixed under an older number.

Fix

Update GitLab to 14.4.1 · 14.3.4 · 14.2.6

Advisories and patches

gitlab.comVendor Advisory

Detection

Nuclei template: none so far
Exploit-DB: no entry
Proof-of-concept repositories: none listed

Sources

CNACVSS 3.18.7read 2026-10-23
NVDCVSS 3.16.1read 2026-10-23
NVDCVSS 2.04.3read 2026-10-23
NVDweakness (CWE)CWE-79read 2026-10-23
FIRST EPSSEPSS score60.7 %read 2026-10-23

Technical details

CVSS v3 Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N
Published: 2021-11-05
Last Modified: 2026-06-17
NVD status: Modified

Frequently asked questions

What is CVE-2021-39906?

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.

Is CVE-2021-39906 actively exploited?

Active exploitation of CVE-2021-39906 has not been confirmed. Its EPSS score was 60.7% on 2026-10-22, the estimated probability of exploitation in the next 30 days.

What is the CVSS score for CVE-2021-39906?

CVE-2021-39906 has a CVSS v3 base score of 6.1 (MEDIUM severity), with vector string CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N.

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