CVE-2016-2194 in Botan
Summary
by MITRE
The ressol function in Botan before 1.10.11 and 1.11.x before 1.11.27 allows remote attackers to cause a denial of service (infinite loop) via unspecified input to the OS2ECP function, related to a composite modulus.
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Analysis
by VulDB Data Team • 08/19/2022
The vulnerability identified as CVE-2016-2194 represents a critical denial of service flaw within the Botan cryptographic library, affecting versions prior to 1.10.11 and 1.11.x before 1.11.27. This issue manifests through the ressol function which processes inputs destined for the OS2ECP function, creating a scenario where maliciously crafted data can trigger an infinite loop condition. The vulnerability specifically relates to composite modulus handling within elliptic curve cryptographic operations, making it particularly dangerous in environments where cryptographic processing is frequent or critical to system operation.
The technical implementation of this vulnerability stems from inadequate input validation within the mathematical operations that govern elliptic curve cryptography. When the OS2ECP function receives malformed or specially crafted input data related to composite modulus values, the ressol function fails to properly terminate its execution cycle. This creates an infinite loop condition that consumes system resources indefinitely, effectively rendering the affected system unavailable to legitimate users. The flaw operates at the mathematical algorithmic level rather than at the protocol or network layer, making it particularly insidious as it can be triggered through cryptographic operations that are fundamental to secure communications.
From an operational perspective, this vulnerability presents a significant risk to systems relying on Botan for cryptographic operations, particularly those implementing elliptic curve cryptography for digital signatures, key exchange, or certificate validation. An attacker could exploit this flaw by sending specially crafted cryptographic data to any service using vulnerable Botan versions, causing denial of service conditions that could impact web servers, email systems, or any application requiring secure cryptographic processing. The infinite loop consumes CPU resources and can potentially lead to system crashes or resource exhaustion that affects overall system availability and performance.
The vulnerability maps to CWE-835, which specifically addresses the issue of infinite loops in software systems, and aligns with ATT&CK technique T1499.004, which covers network denial of service attacks. Organizations using vulnerable versions of Botan should implement immediate patching strategies to upgrade to versions 1.10.11 or 1.11.27 and later, which contain the necessary fixes to properly handle composite modulus inputs. Additionally, network segmentation and input validation measures can provide additional defense-in-depth layers to mitigate potential exploitation attempts. System monitoring should be enhanced to detect unusual CPU consumption patterns that might indicate exploitation attempts, and regular security assessments should verify that all cryptographic libraries are updated to their latest secure versions to prevent similar vulnerabilities from compromising system integrity.