Security readout for executives and security teams
Plain-English summary
This GitLab flaw allowed unauthenticated external users to trigger server-side requests through the CI Lint API. For leaders, the concern is data exposure from GitLab reaching internal or protected resources. CISA KEV inclusion means known exploitation is reported, so exposed GitLab instances should be treated as urgent even though the CVSS score is medium.
Executive priority
High priority for affected GitLab deployments because KEV listing indicates known exploitation and the issue can expose sensitive internal resources through GitLab’s network position.
Technical view
CVE-2021-39935 is a CWE-918 SSRF in GitLab CE/EE CI Lint API. It affects versions from 10.5 before 14.3.6, 14.4 before 14.4.4, and 14.5 before 14.5.2. The CVSS vector is network-accessible, unauthenticated, high complexity, scope-changed, with high confidentiality impact and no integrity or availability impact.
Likely exposure
Organizations running self-managed GitLab CE/EE in the affected version ranges are the likely exposure group, especially internet-facing instances with unauthenticated reachability to the CI Lint API.
Exploitation context
CISA KEV status supports known exploitation. The provided sources do not include exploit prevalence, detailed attacker behavior, or exploitation timeline. SSRF impact depends on what internal services the GitLab server can reach.
Researcher notes
The source bundle establishes affected versions, CWE, CVSS, and KEV status. It does not provide safe operational indicators, exploit volume, or a standalone mitigation besides upgrading/checking vendor guidance. Validate exposure without reproducing SSRF behavior.
Mitigation direction
- Upgrade GitLab CE/EE to 14.3.6, 14.4.4, 14.5.2, or later as applicable.
- Prioritize internet-facing self-managed GitLab instances first.
- Check GitLab vendor guidance for any supported temporary controls.
- Review network egress paths from GitLab to sensitive internal services.
- Keep GitLab on supported security releases after remediation.
Validation and detection
- Inventory all self-managed GitLab CE/EE versions.
- Compare installed versions against the affected ranges listed by GitLab.
- Confirm whether the CI Lint API is reachable by unauthenticated external users.
- Review GitLab access logs for unusual CI Lint API activity.
- Confirm remediation by verifying the upgraded GitLab version.
Public sources used
Generated from the cited source records. This long-tail analysis has not been individually reviewed by a named human.
Conservative CVE-to-ATT&CK context
These mappings and lookup hints may be relevant to the vulnerability behavior, CWE, affected product, or exposure path. Glexia-inferred context is not an official MITRE, ATT&CK, CWE, or CVE Program mapping.
ATT&CK lookup starting points
Use these exact CWE pages and searches to review the Glexia ATT&CK library from this CVE's weakness and description context.
CWE-918: Information exposure and cloud metadata lookup
Information exposure and SSRF weaknesses can make discovery, cloud metadata, and credential material review relevant. Open the exact CWE lookup page first, then review the ATT&CK searches from that MITRE weakness context. This is a Glexia lookup hint, not an official ATT&CK mapping.
Open ATT&CK lookupCVE-2021-39935 mapping review
Open the CVE-to-ATT&CK bridge for reviewed, inferred, or future official mappings tied to this CVE.
Open ATT&CK lookup- Severity
- Medium
- CVSS
- 6.8 (3.1)
- Known Exploited
- Yes
- Published
Vector: CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:C/C:H/I:N/A:N
CNA and ADP enrichment extracted from CVE v5
These fields come from the CVE record and ADP containers, not from Glexia's Take. They preserve time-varying source decisions such as CISA SSVC, KEV status, CVSS metrics, and provider references.
CISA KEV status
CVSS vector scores
1 official scoreWe collect every scored CVSS vector available in the official CNA and ADP containers. When more than one version is present, the table keeps the source vectors side by side instead of collapsing them into the highest score.
CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:C/C:H/I:N/A:N2.24Primary CVE scoreVulnerability scoring details
Base CVSS 3.1 score
6.8MediumVector: CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:C/C:H/I:N/A:N
Source materials
- CVE List V5 sourceCVE List V5
- https://gitlab.com/gitlab-org/gitlab/-/issues/346187CVE reference · x_refsource_MISC
- https://hackerone.com/reports/1236965CVE reference · x_refsource_MISC
- https://gitlab.com/gitlab-org/cves/-/blob/master/2021/CVE-2021-39935.jsonCVE reference · x_refsource_CONFIRM
- https://www.cisa.gov/known-exploited-vulnerabilities-catalog?field_cve=CVE-2021-39935CVE reference · government-resource
Products and packages named in the record
CWE details
CWE links open Glexia weakness intelligence pages with official CWE context, developer remediation guidance, and related CVE mappings.
Server-Side Request Forgery (SSRF)
Server-Side Request Forgery (SSRF) represents a recurring weakness pattern that can create exploitable paths when design, validation, or implementation controls are missing.