Threats / GitLab / CVE-2021-39935
CVE-2021-39935
· EUVD no mirror located
· GCVE no mirror located
Verified 2026-09-19
GitLab Community and Enterprise Editions vulnerability
GitLab Community and Enterprise Editions contain a server-side request forgery vulnerability in the CI Lint API that allows unauthorized external users to perform arbitrary server-side requests.
Verdict
Today item — known-exploited.
An unauthenticated attacker can exploit SSRF via the CI Lint API to make requests from the GitLab server to internal or external systems, potentially accessing sensitive data, internal services, or launching further attacks against network infrastructure.
CISA KEV Yes · 2026-02-035EPSS 0.35649 (verify live)6CVSS 6.83CISA SSVC Exploitation: active · Automatable: no · Impact: partial4
01
Is it exploitable?
— the evidence, ranked above the scoreReported exploitation
4 independent public reports of in-the-wild exploitation are cataloged.Distinct reporting sources (vendor, incident response, government); open them for the underlying claims.
Exploited in the wild
Listed in the CISA Known Exploited Vulnerabilities catalog (added 2026-02-03).
Probability (EPSS)
EPSS 0.35649 — modeled likelihood of exploitation activity.EPSS is a daily-changing model output — open the source for today's value.
Severity / affected
CVSS 6.8 (CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:C/C:H/I:N/A:N) · Affected: GitLab, Community and Enterprise Editions. Confirm exact fixed builds in the vendor advisory.CVSS — CNA-assigned (CVE.org), version 3.1, set at disclosure.
Weakness (CWE)
Mapped to CWE-918 Server-Side Request Forgery (SSRF).CWE assignment from the public NVD record (may be stale); the weakness class drives how the flaw is exploited.
CISA SSVC (triage disposition)
Exploitation: active · Automatable: no · Technical Impact: partialCISA's own stakeholder-specific triage inputs, published in the CVE record (CISA Coordinator role). NOTE: this is CISA's three decision points; the final Act/Attend/Track decision also requires a Mission & Well-being input not published here, so no overall decision is asserted.
Currency of the record
CISA added this to its KEV catalog 1513 days after the CVE record was published.KEV lag = CISA-KEV dateAdded − CVE.org datePublished; a floor on how long the known-exploited flaw sat in the public record before the federal catalog listed it. Severity/weakness here is CNA- or CISA-assigned (current at disclosure), independent of NVD's analysis backlog.
02
Who’s exploiting it?
— attribution turns risk into urgencyAttribution not established
No confirmed (advisory-backed) threat-actor attribution is established for this record. Absence of a named actor is not absence of compromise — see Coverage & confidence.
03
Why it matters
— the attack path, told twice: adversary, then board1
Front door — unauthenticated access narrative 1
Attacker
I craft a malicious CI Lint API request that causes the GitLab server to make HTTP requests to internal network addresses or services I specify.
Business
Internal services and resources become accessible to external attackers without authentication, exposing sensitive data and system topology.
2
Keys to the kingdom — privilege/identity takeover narrative 2
Attacker
I use the SSRF to probe and enumerate internal services, cloud metadata endpoints, or private APIs running on the same network as GitLab.
Business
Attackers gain reconnaissance of internal infrastructure, increasing risk of lateral movement and targeted secondary attacks.
3
Lateral reach — past segmentation narrative 3
Attacker
I leverage the server-side request capability to interact with internal APIs or services that trust the GitLab server, bypassing network segmentation.
Business
Trust relationships between systems are compromised, allowing attackers to pivot to other critical infrastructure components.
04
What to do
— defensible action- Remediate per the vendor advisory — confirm the fixed build for your version and verify exposure.1
Say it to the boardA vulnerability with this evidence profile is a defensible budget line, not a backlog ticket — fund the change against the proof above.
05
Coverage & confidence
— what we know, and what we don’tEstablished (cited)
Coverage gaps — stated, not hidden
Disclosure & credit2
Catalogued by GitLabCNA
Credited with finding itThanks @minhli for reporting this vulnerability through our HackerOne bug bounty programunspecified
Found an error? Propose a correction.
A correction is a cited counter-claim — it must cite a source,
gets reviewed by a second human, and is never auto-applied. See the
correction convention and our identity
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