How severe is CVE-2021-39906?

CVE-2021-39906 has a CVSS 3.x base score of 8.7, rated high severity. It is exploitable over network with low attack complexity, requires low privileges and user interaction. Impact on confidentiality is high, integrity high, and availability none.

Is CVE-2021-39906 being actively exploited?

It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 61% (99th percentile), an estimate of the probability of exploitation in the next 30 days.

What products are affected by CVE-2021-39906?

CVE-2021-39906 primarily affects Gitlab. In total, 2 product configurations (CPEs) are listed as vulnerable; see the affected-products list for the exact versions.

How do I fix CVE-2021-39906?

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.

When was CVE-2021-39906 published?

CVE-2021-39906 was published on 2021-11-05 and last updated on 2026-06-17.

CVE-2021-39906

CVE-2021-39906 is a high-severity vulnerability in Gitlab with a CVSS 3.x base score of 8.7. Its EPSS exploit-prediction score of 61% places it in the 99th percentile, indicating an elevated likelihood of exploitation. The underlying weakness is classified as CWE-79.

Key facts

Severity: High (CVSS 3.x base score 8.7)
CVSS v2: 4.3
EPSS exploit prediction: 61% (99th percentile)
Actively exploited: Not listed in CISA KEV
Weakness: CWE-79
Affected product: Gitlab
Published: 2021-11-05
Last modified: 2026-06-17

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.

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.
How severe is CVE-2021-39906?: CVE-2021-39906 has a CVSS 3.x base score of 8.7, rated high severity. It is exploitable over network with low attack complexity, requires low privileges and user interaction. Impact on confidentiality is high, integrity high, and availability none.
Is CVE-2021-39906 being actively exploited?: It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 61% (99th percentile), an estimate of the probability of exploitation in the next 30 days.
What products are affected by CVE-2021-39906?: CVE-2021-39906 primarily affects Gitlab. In total, 2 product configurations (CPEs) are listed as vulnerable; see the affected-products list for the exact versions.
How do I fix CVE-2021-39906?: 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.
When was CVE-2021-39906 published?: CVE-2021-39906 was published on 2021-11-05 and last updated on 2026-06-17.

References

Affected products (2)

cpe:2.3:a:gitlab:gitlab:*:*:*:*:community:*:*:*
cpe:2.3:a:gitlab:gitlab:*:*:*:*:enterprise:*:*:*

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