CVE-2021-39935
An issue has been discovered in GitLab CE/EE affecting all versions starting from 10.5 before 14.3.6, all versions starting from 14.4 before 14.4.4, all versions starting from 14.5 before 14.5.2. Unauthorized external users could perform Server Side Requests via the CI Lint API
do firstApply mitigations per vendor instructions, follow applicable BOD 22-01 guidance for cloud services, or discontinue use of the product if mitigations are unavailable.
Can a WAF block it? Partly. The vulnerability involves unauthorized external users sending HTTP requests to the CI Lint API, which can be identified by the specific API endpoint and parameters used to trigger server-side requests. A WAF rule can match requests to the CI Lint API endpoint with unusual parameters triggering SSRF. No tracked WAF vendor has published a rule for this CVE yet, so you would write it yourself.
What a custom rule would match: requests to the CI Lint API endpoint with unusual parameters triggering SSRF
Also consider: patch · custom WAF rule · egress filter · IMDSv2
Based on an AI reading of the CVE description, and no vendor rule found yet. We check Cloudflare, AWS, Google Cloud Armor and Azure; for Akamai, Imperva, Fastly, F5, ask your vendor.
Is CVE-2021-39935 being exploited?
Yes. CVE-2021-39935 appears in CISA's Known Exploited Vulnerabilities catalog, which means exploitation in the wild has been confirmed and reported. Treat it as active rather than theoretical, and patch it ahead of higher-scoring vulnerabilities that carry no exploitation evidence.
How severe is CVE-2021-39935?
CVE-2021-39935 is rated Medium with a CVSS score of 6.8. Severity describes how bad exploitation would be, not how likely it is: pair it with exploitation evidence before deciding what to patch first.
Is there a patch for CVE-2021-39935?
Yes. A fix has been recorded for CVE-2021-39935. The vendor advisory is the authority on the exact fixed version — apply it from there rather than from a summary.
What does CVE-2021-39935 affect?
CVE-2021-39935 affects gitlab:gitlab. Confirm the exact affected versions against the vendor advisory before deciding you are exposed.
Exploitation status reflects CISA's KEV catalog as we last synced it. Check the catalog directly.
- affected>= 10.5 and < 14.3.6
- affected>= 14.4 and < 14.4.4
- affected>= 14.5 and < 14.5.2
As published in the CVE Program record. A version outside these ranges is not a statement that it is unaffected — vendors sometimes understate a range, and distribution-backported builds carry upstream numbers that do not reflect what was patched into them.
cisa ssvc
- exploitation
- active
- automatable
- no
- technical impact
- partial
Assessed by CISA 3 Feb 2026 (SSVC 2.0.3).
timeline
- 13 Dec 2021Published
- 3 Feb 2026Added to CISA KEV (exploited in the wild) · 1,512 days (about 4 years) later
- 3 Feb 2026CISA SSVC assessment: exploitation active · 1 day later
- 3 Feb 2026CVE record last updated · same day later
- 24 Feb 2026CISA remediation due date (US federal agencies) · 20 days later
- 2 Nov 2026Analysed by vulneraibility.com · 252 days (about 8 months) later
- Linkgitlab.com /gitlab-org/gitlab/-/issues/346187
- Linkhackerone.com /reports/1236965
- Linkgitlab.com /gitlab-org/cves/-/blob/master/2021/CVE-2021-39935.json
- Linkcisa.gov /known-exploited-vulnerabilities-catalog?field_cve=CVE-2021-39935
sources
- CVE List (CVE.org): description, affected versions, references; CVE Terms of Use
- NVD: CVSS and CPE data
- CISA KEV catalog: exploitation, date added, due date
- CISA Vulnrichment (ADP): SSVC decision points
- FIRST EPSS: exploit probability and percentile
- Summary, impact and triage tags: written by our AI analysis pipeline from the sources above. Check them against the sources.