CVE-2009-2825 in Mac OS X
Summary
by MITRE
Certificate Assistant in Apple Mac OS X before 10.6.2 does not properly handle a \0 character in a domain name in the subject s Common Name (CN) field of an X.509 certificate, which might allow 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 • 06/02/2025
The vulnerability described in CVE-2009-2825 represents a critical certificate validation flaw within Apple Mac OS X versions prior to 10.6.2, specifically affecting the Certificate Assistant component. This issue stems from improper handling of the null character within the Common Name field of X.509 certificates, creating a significant security gap that enables malicious actors to conduct man-in-the-middle attacks. The flaw exploits the way the operating system processes domain names in certificate subject information, particularly when null characters are present in the Common Name field. This vulnerability is closely related to CVE-2009-2408, indicating a broader class of certificate handling issues that affect SSL/TLS security implementations. The technical root cause resides in the insufficient input validation and sanitization of certificate subject fields, specifically targeting the Common Name attribute which is crucial for SSL certificate verification processes. This flaw directly impacts the trust model of SSL certificates by allowing attackers to craft certificates that appear legitimate while containing malicious null character sequences that bypass normal validation checks. The vulnerability operates at the application layer of the OSI model, specifically affecting the TLS/SSL handshake process where certificate validation occurs, and represents a violation of the fundamental security principle that certificate validation must be robust against malformed inputs. From a cybersecurity perspective, this issue falls under the category of certificate validation failures that can lead to certificate forgery and trust exploitation, aligning with CWE-248, which addresses the improper handling of exceptional conditions in software components.
The operational impact of CVE-2009-2825 extends beyond simple certificate validation failures to encompass a complete compromise of SSL/TLS security assurances within affected Mac OS X environments. Attackers can exploit this vulnerability by creating malicious certificates that contain null characters in their Common Name fields, enabling them to impersonate legitimate SSL servers without detection. This capability undermines the entire public key infrastructure trust model, as users and applications would trust certificates that appear valid but actually contain malicious payloads. The vulnerability is particularly dangerous because it allows attackers to bypass certificate validation mechanisms that are supposed to prevent man-in-the-middle attacks, effectively neutralizing SSL security protections for affected systems. The null character handling issue specifically affects how certificate assistants process domain name validation, creating a window where attackers can inject malformed certificate data that the system accepts as legitimate. This flaw can be exploited in various attack scenarios including web traffic interception, email security breaches, and any application relying on SSL/TLS certificate validation for authentication. The impact is severe enough to potentially allow full network traffic interception and data exfiltration, making it a high-priority vulnerability for organizations relying on Mac OS X systems for secure communications. The vulnerability's exploitation requires minimal technical expertise, as it leverages existing certificate generation capabilities combined with the specific null character handling flaw, making it particularly dangerous in enterprise environments where SSL security is critical.
Mitigation strategies for CVE-2009-2825 primarily focus on immediate system updates and enhanced certificate validation practices. The most effective solution involves upgrading affected Mac OS X systems to version 10.6.2 or later, where Apple implemented proper null character handling in certificate validation routines. Organizations should also implement additional certificate monitoring and validation procedures, including manual verification of certificate chains and implementation of certificate pinning mechanisms where possible. Network administrators should consider deploying certificate transparency monitoring solutions to detect potentially malicious certificates before they can be used in attacks. The vulnerability highlights the importance of robust input validation in security-critical components, as demonstrated by the ATT&CK framework's emphasis on input validation and sanitization techniques. Security teams should also consider implementing network-level certificate inspection tools that can detect and block certificates containing null characters or other malformed sequences before they reach end-user systems. Organizations may need to temporarily disable or restrict SSL/TLS connections to high-risk domains until systems can be properly updated. The vulnerability serves as a reminder of the critical importance of thorough testing of certificate handling components, particularly those that interact with user-facing applications like certificate assistants, and emphasizes the need for comprehensive security testing that includes edge cases and malformed inputs. Proper patch management and vulnerability assessment procedures should include specific checks for certificate validation routines to prevent similar issues from arising in other software components.