Attack Chain

1. A remote attacker crafts a malicious XML Schema Definition (XSD) string designed to trigger either Server-Side Request Forgery (SSRF) or local file read primitives.
2. The attacker delivers this crafted XSD string as input to the file_type content detector within the vulnerable guardrails-detectors component.
3. The guardrails-detectors component processes the arbitrary XSD string without proper restrictions, enabling the embedded malicious directives.
4. The exploitation results in the guardrails-detectors system initiating unauthorized server-side requests to internal or external arbitrary URLs (SSRF).
5. Concurrently or alternatively, the exploitation allows the attacker to read arbitrary local files from the compromised system.
6. Through local file reads, the attacker exfiltrates sensitive information such as cloud provider credentials, configuration files, or other sensitive data.
7. Leveraging the SSRF capabilities, the attacker gains unauthorized access to internal network services, potentially facilitating lateral movement or further information disclosure within the network.

Impact

Successful exploitation of CVE-2026-15143 carries a CVSS v3.1 Base Score of 9.3, indicating critical severity. The primary impact involves sensitive information disclosure, potentially compromising crucial assets such as cloud provider credentials. This can grant attackers unauthorized access to cloud resources, leading to data breaches, resource manipulation, or further attacks on cloud infrastructure. Additionally, the ability to read local files allows attackers to steal proprietary data, configuration files, or user information directly from the server. The Server-Side Request Forgery (SSRF) aspect enables attackers to bypass network perimeter defenses, access internal network services, scan internal networks, or interact with other internal systems, significantly broadening the scope of potential damage and facilitating deeper penetration into the target environment.

Recommendation

• Patch CVE-2026-15143 on all affected guardrails-detectors installations immediately to prevent remote exploitation.
• Implement strong egress filtering to restrict outbound connections from guardrails-detectors instances to only necessary and approved destinations, mitigating the impact of potential SSRF exploits.
• Monitor network logs for suspicious outbound connections originating from the guardrails-detectors application to unusual or internal IP addresses that align with potential SSRF activity.
• Implement file integrity monitoring on critical files (e.g., configuration files, credential stores) accessed by guardrails-detectors to detect unauthorized local file reads.