CVE-2012-5668 in FreeType
Summary
by MITRE
FreeType before 2.4.11 allows context-dependent attackers to cause a denial of service (NULL pointer dereference and crash) via vectors related to BDF fonts and the improper handling of an "allocation error" in the bdf_free_font function.
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Analysis
by VulDB Data Team • 04/20/2021
The vulnerability identified as CVE-2012-5668 represents a critical denial of service flaw within the FreeType font rendering library, which is widely deployed across operating systems and applications for handling font processing. This issue affects FreeType versions prior to 2.4.11 and stems from improper error handling mechanisms within the BDF (Bitmap Distribution Format) font processing subsystem. The vulnerability manifests when the library encounters malformed or malicious BDF font files, leading to a NULL pointer dereference that ultimately causes application crashes and system instability.
The technical root cause of this vulnerability lies in the bdf_free_font function's inadequate handling of allocation errors during font memory management operations. When processing BDF fonts, FreeType attempts to allocate memory for font data structures, but in certain error conditions, the allocation failure is not properly managed. This results in the function attempting to dereference a NULL pointer, which triggers an immediate crash of the affected application. The vulnerability is context-dependent because it requires specific conditions to be met during font processing, namely the presence of malformed BDF fonts and the particular sequence of memory allocation failures that occur during font cleanup operations.
The operational impact of CVE-2012-5668 extends beyond simple application crashes, as it can be exploited to create persistent denial of service conditions across multiple software platforms that rely on FreeType for font rendering. This includes web browsers, office suites, desktop environments, and system applications that process font files. Attackers can craft malicious BDF font files that trigger the NULL pointer dereference when opened or rendered, potentially allowing them to disrupt services, cause system instability, or create opportunities for more sophisticated attacks. The vulnerability's exploitation is particularly concerning in environments where automated font processing occurs, such as web browsers automatically downloading and rendering fonts from untrusted sources.
From a cybersecurity perspective, this vulnerability aligns with CWE-476, which describes NULL pointer dereference conditions, and represents a classic example of improper error handling in memory management operations. The ATT&CK framework categorizes this as a Denial of Service attack technique, specifically under the T1499.004 sub-technique for Network Denial of Service. Organizations should prioritize immediate patching of affected systems to mitigate this vulnerability, as the exploit requires minimal technical expertise and can be easily automated. Additionally, implementing proper input validation and sandboxing mechanisms for font processing operations can provide additional defense-in-depth measures against similar vulnerabilities in the future.
The remediation strategy for CVE-2012-5668 involves upgrading to FreeType version 2.4.11 or later, which includes proper error handling for allocation failures in the BDF font processing code. System administrators should also consider implementing font validation mechanisms and restricting font processing to trusted sources where possible. Regular security assessments of font handling components and monitoring for unusual font processing patterns can help detect potential exploitation attempts. Given the widespread use of FreeType in various software ecosystems, coordinated patching across affected applications and operating systems is essential to prevent exploitation of this vulnerability.