CVE-2026-1699
Published: 30 January 2026
Summary
CVE-2026-1699 is a critical-severity Inclusion of Functionality from Untrusted Control Sphere (CWE-829) vulnerability in Eclipse Theia Website. Its CVSS base score is 10.0 (Critical).
Operationally, exploitation aligns with the MITRE ATT&CK technique Compromise Software Supply Chain (T1195.002); ranked at the 39.1th percentile by exploit likelihood (below the median); it is not currently listed in the CISA KEV catalog; a public proof-of-concept is referenced.
The strongest mitigations our analysis identified are NIST 800-53 AC-6 (Least Privilege) and CM-5 (Access Restrictions for Change).
Deeper analysis
CVE-2026-1699 is a critical vulnerability (CVSS 10.0, CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:H/I:H/A:H) affecting the Eclipse Theia Website repository. The issue resides in the GitHub Actions workflow file .github/workflows/preview.yml, which uses the pull_request_target trigger while checking out and executing untrusted pull request code. This misconfiguration, tied to CWE-829 (Inclusion of Functionality from Untrusted Control Sphere), exposes the CI environment to arbitrary code execution.
Any GitHub user can exploit this vulnerability by submitting a malicious pull request, triggering the workflow to run untrusted code with elevated privileges. The code executes in the repository's CI environment, gaining access to repository secrets and a GITHUB_TOKEN with broad write permissions (contents:write, packages:write, pages:write, actions:write). Successful exploitation allows attackers to exfiltrate secrets, publish malicious packages to the eclipse-theia organization, modify the official Theia website, and push malicious code directly to the repository.
Mitigation details are documented in the Eclipse security advisory at https://gitlab.eclipse.org/security/vulnerability-reports/-/issues/332, published on 2026-01-30.
OWASP Top 10 for Web (2025)
EU & UK References
- 🇪🇺 ENISA EUVD: EUVD-2026-5040
Vulnerability details
In the Eclipse Theia Website repository, the GitHub Actions workflow .github/workflows/preview.yml used pull_request_target trigger while checking out and executing untrusted pull request code. This allowed any GitHub user to execute arbitrary code in the repository's CI environment with access to…
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repository secrets and a GITHUB_TOKEN with extensive write permissions (contents:write, packages:write, pages:write, actions:write). An attacker could exfiltrate secrets, publish malicious packages to the eclipse-theia organization, modify the official Theia website, and push malicious code to the repository.
- CWE(s)
Related Threats
MITRE ATT&CK Enterprise TechniquesAI
Why these techniques?
Vuln directly enables supply-chain compromise via malicious PR code exec in CI (T1195.002), arbitrary command execution (T1059), and credential/secret exfiltration (T1552.001).
CVEs Like This One
Affected Assets
Mitigating Controls
Mitigating Controls (NIST 800-53 r5) AI
Requires establishment and enforcement of secure configuration settings for GitHub Actions workflows to prevent use of pull_request_target trigger with untrusted code execution.
Enforces least privilege on GITHUB_TOKEN permissions in CI environments, limiting damage from arbitrary code execution by restricting write access to contents, packages, pages, and actions.
Restricts modifications to configuration-controlled workflow files like preview.yml to authorized roles, preventing introduction or persistence of vulnerable trigger configurations.