CVE-2015-7825 in Botan
Summary
by MITRE
botan before 1.11.22 improperly validates certificate paths, which allows remote attackers to cause a denial of service (infinite loop and memory consumption) via a certificate with a loop in the certificate chain.
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Analysis
by VulDB Data Team • 08/28/2020
The vulnerability identified as CVE-2015-7825 affects the Botan cryptographic library version 1.11.22 and earlier, presenting a critical security flaw in certificate path validation mechanisms. This issue stems from inadequate validation of certificate chains that can contain loops, creating a scenario where the library fails to properly terminate certificate chain traversal operations. The flaw specifically impacts the certificate validation process within the library's X.509 certificate handling functionality, which is fundamental to secure communications in numerous applications relying on Botan for cryptographic operations.
The technical implementation of this vulnerability resides in the certificate path validation algorithm that lacks proper loop detection mechanisms. When processing a certificate chain containing a loop, the validation routine enters an infinite loop where it continuously traverses the same certificates without recognizing the circular reference. This condition results in unbounded memory consumption as the validation process continues indefinitely, consuming system resources and ultimately leading to denial of service conditions. The vulnerability manifests when the library attempts to validate a certificate chain that contains a reference to a previously encountered certificate, creating a cycle that the validation logic cannot break.
From an operational perspective, this vulnerability presents significant risks to systems utilizing Botan for secure communications, particularly in environments where certificate validation is performed automatically. Attackers can exploit this weakness by presenting maliciously crafted certificates containing loops in their chains, causing targeted services to consume excessive CPU cycles and memory resources. The impact extends beyond simple resource exhaustion, as the infinite loop can effectively render affected systems unavailable to legitimate users, creating a denial of service condition that can persist until the affected process is manually terminated or the system is rebooted. This vulnerability particularly affects applications that perform automatic certificate validation without proper bounds checking or timeout mechanisms.
Mitigation strategies for CVE-2015-7825 require immediate implementation of the patched version of Botan library, specifically version 1.11.22 or later, which includes proper loop detection and termination logic in certificate path validation. Organizations should conduct comprehensive vulnerability assessments to identify all systems utilizing vulnerable versions of Botan and implement patch management procedures to ensure timely updates. Additionally, implementing certificate validation timeouts and resource limits can provide additional defense-in-depth measures, preventing exploitation even if patches are not immediately applied. Security monitoring should be enhanced to detect unusual memory consumption patterns or process behavior that might indicate exploitation attempts. This vulnerability aligns with CWE-838, which addresses insufficient input validation, and maps to ATT&CK technique T1499.004 for denial of service via resource exhaustion, emphasizing the importance of proper input validation and resource management in cryptographic libraries.
The broader implications of this vulnerability extend to the security posture of systems relying on Botan, as certificate validation failures can compromise the entire trust model of secure communications. Organizations should consider implementing certificate pinning mechanisms and additional validation layers to reduce dependency on the vulnerable library's path validation logic. Regular security audits of cryptographic libraries and their usage patterns should be conducted to identify similar vulnerabilities in other components of the security infrastructure. The vulnerability also highlights the critical importance of robust input validation in cryptographic operations, where malformed inputs can lead to catastrophic system failures rather than simple error conditions.