CVE-2020-4099 in Verse
Summary
by MITRE • 11/01/2022
The application was signed using a key length less than or equal to 1024 bits, making it potentially vulnerable to forged digital signatures. An attacker could forge the same digital signature of the app after maliciously modifying the app.
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Analysis
by VulDB Data Team • 11/30/2022
This vulnerability represents a critical cryptographic weakness in digital signature validation mechanisms that undermines the integrity and authenticity guarantees typically provided by software signing processes. The issue stems from the use of insufficient key length in the cryptographic algorithm employed for application signing, specifically when the RSA key length falls below the recommended minimum threshold of 1024 bits. According to the CWE catalog, this maps to CWE-327 which identifies the use of weak cryptographic algorithms and key sizes as a fundamental security flaw that directly enables man-in-the-middle attacks and digital signature forgery scenarios. The vulnerability exists at the core of software supply chain security where digital signatures serve as the primary mechanism for verifying software authenticity and integrity.
The technical flaw manifests when an attacker exploits the mathematical weaknesses inherent in short key lengths to compute equivalent signatures for modified software versions. With RSA keys shorter than 1024 bits, the computational complexity required to break the encryption becomes feasible through modern computational resources and specialized attack techniques such as factoring attacks or brute force methods. This vulnerability directly violates industry standards including those outlined in NIST SP 800-57 and the ISO/IEC 14443 standard for cryptographic key management, which mandate minimum key lengths to ensure adequate security margins against contemporary cryptanalytic capabilities. The operational impact extends beyond simple code modification as it compromises the entire trust model that software distribution platforms rely upon for secure delivery.
The implications of this vulnerability create a dangerous environment where attackers can successfully bypass security controls designed to prevent unauthorized modifications to legitimate applications. This attack vector enables sophisticated supply chain compromises where malicious actors can inject backdoors or malware into applications that appear to be authentic and properly signed. The attack pattern aligns with techniques described in the MITRE ATT&CK framework under T1553.002 - "Subvert Trust Controls" which specifically addresses methods for bypassing code signing validation mechanisms. Organizations using affected applications face potential exposure to persistent threats where the attacker can maintain long-term access through legitimate signed applications that have been subtly modified to include malicious payloads.
Mitigation strategies must address both immediate remediation and long-term architectural improvements to prevent similar vulnerabilities in future deployments. The primary recommendation involves implementing cryptographic key rotation with minimum 2048-bit RSA keys or equivalent elliptic curve cryptography to ensure adequate security margins. Software vendors should also implement comprehensive key management processes that include regular security assessments, automated monitoring for weak cryptographic implementations, and adherence to established security frameworks such as the OWASP Cryptographic Requirements. Additionally, organizations should deploy signature validation mechanisms that perform thorough integrity checks beyond simple signature verification, including runtime monitoring for unexpected behavioral changes that might indicate compromise of signed applications. The vulnerability underscores the importance of maintaining current cryptographic standards and the necessity of regular security audits to identify and remediate weak cryptographic implementations before they can be exploited by adversaries.