CVE-2009-2702 in kdelibs
Summary
by MITRE
KDE KSSL in kdelibs 3.5.4, 4.2.4, and 4.3 does not properly handle a \0 character in a domain name in the Subject Alternative Name field of an X.509 certificate, which allows man-in-the-middle attackers to spoof arbitrary SSL servers via a crafted certificate issued by a legitimate Certification Authority, a related issue to CVE-2009-2408.
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Analysis
by VulDB Data Team • 08/22/2021
The vulnerability identified as CVE-2009-2702 represents a critical flaw in the KDE KSSL implementation within kdelibs versions 3.5.4, 4.2.4, and 4.3. This security weakness specifically targets the handling of domain names within the Subject Alternative Name field of X.509 certificates, creating a significant attack vector for man-in-the-middle operations. The flaw stems from improper validation of null character sequences within domain name identifiers, allowing malicious actors to craft certificates that appear legitimate while actually enabling unauthorized interception of secure communications. This vulnerability directly impacts the trust model that SSL/TLS protocols rely upon for establishing secure connections between clients and servers. The issue is categorized under CWE-264, which addresses permissions, privileges, and access control failures, specifically manifesting in certificate validation mechanisms that should enforce strict domain name matching requirements. The vulnerability operates at the application layer of the OSI model, affecting SSL/TLS certificate verification processes within the KDE desktop environment's networking stack.
The technical implementation of this flaw occurs when the KDE KSSL component processes X.509 certificates containing null characters within the Subject Alternative Name field of certificate extensions. When a certificate contains a domain name with a null character sequence, the KSSL implementation fails to properly validate or sanitize this input, leading to a bypass of standard certificate verification procedures. This misconfiguration allows attackers to create certificates that contain domain names with embedded null characters, which the vulnerable system interprets as valid domain matches even when the actual domain differs from the intended target. The attack mechanism exploits the fact that the null character is often used to terminate strings in programming languages, but in certificate validation contexts, such characters should be strictly prohibited. This behavior creates a scenario where a certificate issued by a legitimate Certification Authority can be manipulated to appear as if it validates against any arbitrary domain name, effectively undermining the entire certificate-based trust infrastructure. The vulnerability is closely related to CVE-2009-2408, indicating a broader class of issues within certificate validation logic that affects multiple components within the same software ecosystem.
The operational impact of CVE-2009-2702 extends beyond simple certificate validation failures, creating substantial risks for organizations relying on KDE-based systems for secure communications. Attackers can leverage this vulnerability to perform successful man-in-the-middle attacks against SSL/TLS connections, potentially intercepting sensitive data including login credentials, personal information, and proprietary communications. The implications are particularly severe in enterprise environments where KDE-based applications handle confidential transactions, as the vulnerability allows attackers to impersonate legitimate servers without detection. This flaw undermines the fundamental security guarantees that SSL/TLS certificates are designed to provide, making it possible for malicious actors to establish fraudulent secure connections that appear legitimate to users. The attack can be executed without requiring access to the actual private keys of legitimate certificates, as the vulnerability lies in the validation logic rather than the cryptographic implementation itself. Organizations using affected KDE versions face significant exposure to data breaches, credential theft, and unauthorized access to sensitive systems. The vulnerability affects not only web browsing but also email clients, file transfer applications, and any other KDE-based software that relies on SSL/TLS certificate validation for secure communications.
Mitigation strategies for CVE-2009-2702 require immediate attention through software updates and configuration changes. The most effective remediation involves upgrading to patched versions of kdelibs that properly handle null characters in certificate domain names, specifically versions that address the underlying certificate validation logic. System administrators should implement certificate pinning mechanisms where possible, adding additional layers of security beyond standard certificate validation. Network monitoring solutions should be enhanced to detect anomalous certificate validation patterns that might indicate exploitation attempts. Organizations should also consider implementing strict certificate validation policies that reject certificates containing non-standard characters in domain name fields. The ATT&CK framework categorizes this vulnerability under T1552.001, which covers "Unsecured Credentials," as the vulnerability enables attackers to bypass credential protection mechanisms through certificate manipulation. Additionally, this issue aligns with T1041, "Exfiltration Over C2 Channel," as compromised secure connections can be used to exfiltrate data. Security teams should conduct thorough vulnerability assessments of all KDE-based systems and implement network segmentation to limit the potential impact of successful attacks. Regular security audits of certificate management processes and enforcement of strict certificate validation policies should be implemented to prevent similar vulnerabilities from emerging in the future. The vulnerability demonstrates the critical importance of proper input validation in security-critical components, particularly those handling cryptographic data and trust relationships within software applications.