CVE-2015-1716 in Windows
Summary
by MITRE
Schannel in Microsoft Windows Server 2003 SP2, Windows Vista SP2, Windows Server 2008 SP2 and R2 SP1, Windows 7 SP1, Windows 8, Windows 8.1, Windows Server 2012 Gold and R2, and Windows RT Gold and 8.1 does not properly restrict Diffie-Hellman Ephemeral (DHE) key lengths, which makes it easier for remote attackers to defeat cryptographic protection mechanisms via unspecified vectors, aka "Schannel Information Disclosure Vulnerability."
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Analysis
by VulDB Data Team • 11/30/2024
The schannel information disclosure vulnerability identified as CVE-2015-1716 represents a critical weakness in Microsoft's Secure Channel API implementation across multiple windows operating system versions. This vulnerability specifically targets the Diffie-Hellman Ephemeral key exchange mechanism, which is fundamental to establishing secure communication channels in protocols such as ssl/tls. The flaw allows attackers to potentially reduce the effective key length of DHE exchanges, thereby weakening the cryptographic protection that should safeguard sensitive communications. The vulnerability affects a broad range of Microsoft products including windows server 2003 sp2, windows vista sp2, windows server 2008 sp2 and r2 sp1, windows 7 sp1, windows 8, windows 8.1, windows server 2012 gold and r2, and windows rt gold and 8.1. This extensive scope makes the vulnerability particularly dangerous as it impacts both server and client operating systems across different generations.
The technical implementation flaw stems from schannel's improper restriction of Diffie-Hellman Ephemeral key lengths during secure communication establishment. Normally, DHE key exchange should utilize sufficiently long keys to prevent brute force attacks and maintain cryptographic strength. However, this vulnerability allows remote attackers to manipulate or influence the key exchange process to use shorter keys than intended, effectively weakening the encryption. The unspecified vectors mentioned in the vulnerability description suggest that attackers can exploit this weakness through various attack methods including man-in-the-middle scenarios, protocol downgrade attacks, or by leveraging specific network conditions that trigger the weakened key exchange behavior. This weakness directly violates the cryptographic principles outlined in cwe-327, which addresses the use of weak or broken cryptographic algorithms. The vulnerability essentially creates a situation where attackers can perform cryptanalysis against weakened key exchanges, potentially leading to the compromise of encrypted communications.
The operational impact of CVE-2015-1716 extends beyond simple information disclosure, as it fundamentally undermines the security assurances provided by secure communication protocols. Organizations running affected systems face significant risks including unauthorized access to confidential data, interception of sensitive communications, and potential credential theft. The vulnerability's ability to weaken cryptographic protection mechanisms makes it particularly dangerous in environments where secure communication is critical, such as financial services, healthcare, government communications, and enterprise networks. Attackers can leverage this weakness to perform advanced persistent threat campaigns, conduct surveillance operations, or gain unauthorized access to protected systems. The vulnerability aligns with several attack techniques documented in the mitre att&ck framework, particularly those related to credential access and defense evasion. The weakness can be exploited to bypass security controls that depend on strong cryptographic implementations, potentially allowing attackers to establish persistent access or escalate privileges within compromised networks.
Mitigation strategies for CVE-2015-1716 should prioritize immediate patch deployment through microsoft's security updates, as the vulnerability requires specific code modifications to address the improper key length restrictions in schannel. Organizations should also consider implementing network monitoring to detect unusual key exchange patterns that might indicate exploitation attempts. Configuration changes such as disabling weak cipher suites, enforcing stronger key exchange algorithms, and implementing proper certificate management practices can provide additional layers of protection. System administrators should conduct comprehensive vulnerability assessments to identify all affected systems and ensure proper patch management processes are in place. The remediation process should also include network segmentation to limit the potential impact of successful exploitation attempts and regular security audits to verify that cryptographic configurations remain secure. Organizations should also consider implementing security information and event management solutions to detect anomalous behavior patterns that might indicate attempts to exploit this vulnerability. Given the widespread nature of the affected products, organizations must also evaluate their long-term migration strategies to newer operating system versions that have addressed these cryptographic weaknesses through improved implementation of key exchange mechanisms and stronger default security configurations.