CVE-2023-50981 in Crypto++
Summary
by MITRE • 12/18/2023
ModularSquareRoot in Crypto++ (aka cryptopp) through 8.9.0 allows attackers to cause a denial of service (infinite loop) via crafted DER public-key data associated with squared odd numbers, such as the square of 268995137513890432434389773128616504853.
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Analysis
by VulDB Data Team • 03/06/2026
The vulnerability identified as CVE-2023-50981 affects the Crypto++ cryptographic library version 8.9.0 and earlier, specifically within the ModularSquareRoot function. This flaw represents a critical denial of service vulnerability that can be exploited through carefully crafted DER-encoded public-key data. The issue manifests when the library processes public-key information containing squared odd numbers, creating conditions that lead to infinite loop execution. The targeted square number in the vulnerability description 268995137513890432434389773128616504853 demonstrates the specific mathematical conditions that trigger the problematic behavior. This vulnerability impacts systems that rely on Crypto++ for cryptographic operations, particularly those handling public-key infrastructure components where DER-encoded data is processed.
The technical root cause of this vulnerability lies in the insufficient input validation and boundary checking within the ModularSquareRoot implementation. When the function receives malformed DER data containing specific squared odd numbers, it enters an infinite loop during the mathematical computation process. This occurs because the algorithm fails to properly handle edge cases in modular arithmetic operations, specifically when dealing with large odd numbers that are perfect squares. The function does not implement adequate loop termination conditions or computational limits that would prevent the execution from becoming trapped in repetitive calculations. This flaw aligns with CWE-835, which addresses infinite loops or other forms of indefinite execution, and represents a classic example of insufficient input validation that can be exploited for denial of service attacks.
The operational impact of CVE-2023-50981 extends beyond simple service disruption, as it can affect any application or system that utilizes Crypto++ for cryptographic operations involving public-key data. Systems processing certificates, digital signatures, or public-key exchanges become vulnerable to this attack vector, potentially leading to resource exhaustion and system unavailability. The vulnerability can be particularly dangerous in high-throughput environments where multiple requests are processed simultaneously, as the infinite loop can consume significant CPU resources and potentially impact other services running on the same system. Network services that rely on Crypto++ for SSL/TLS operations, certificate validation, or cryptographic key management are especially at risk, as attackers can craft malicious public-key data to trigger the vulnerability. This type of vulnerability also aligns with ATT&CK technique T1499.004, which covers network denial of service attacks, and represents a form of resource exhaustion that can be classified under the broader category of availability attacks.
Mitigation strategies for CVE-2023-50981 should prioritize immediate patching of affected Crypto++ versions, with version 8.9.1 and later containing the necessary fixes. Organizations should implement input validation measures that sanitize DER-encoded data before processing, particularly when dealing with public-key information. Network segmentation and rate limiting can help reduce the impact of potential attacks by limiting the number of requests that can be processed from a single source. Monitoring systems should be configured to detect unusual CPU usage patterns that might indicate exploitation attempts. Additionally, implementing proper error handling and timeout mechanisms in applications that use Crypto++ can provide defense-in-depth measures. The vulnerability highlights the importance of thorough testing of cryptographic libraries against edge cases and malformed inputs, as recommended by industry standards such as NIST SP 800-57 and ISO/IEC 15408. Organizations should also consider alternative cryptographic libraries that have demonstrated robust handling of edge cases, though such replacements require careful evaluation of compatibility and performance impacts.