CVE-2011-0064 in Pango
Summary
by MITRE
The hb_buffer_ensure function in hb-buffer.c in HarfBuzz, as used in Pango 1.28.3, Firefox, and other products, does not verify that memory reallocations succeed, which allows remote attackers to cause a denial of service (NULL pointer dereference and application crash) or possibly execute arbitrary code via crafted OpenType font data that triggers use of an incorrect index.
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Analysis
by VulDB Data Team • 01/19/2025
The vulnerability identified as CVE-2011-0064 represents a critical memory management flaw within the HarfBuzz text shaping library that affects numerous applications including Pango 1.28.3, Firefox, and other software utilizing this font processing component. This issue stems from inadequate error handling during memory reallocation operations, specifically within the hb_buffer_ensure function located in hb-buffer.c. The flaw manifests when processing crafted OpenType font data that triggers improper memory management behavior, creating potential pathways for both denial of service and arbitrary code execution attacks.
The technical root cause of this vulnerability lies in the hb_buffer_ensure function's failure to validate memory allocation outcomes before proceeding with subsequent operations. When memory reallocation occurs, the function does not check whether the operation completed successfully, potentially leaving pointers in an invalid state. This oversight creates a condition where subsequent code attempts to access memory locations that may have been set to NULL or otherwise corrupted during the failed reallocation process. The vulnerability specifically impacts the handling of incorrect indices within font data structures, where malformed OpenType font files can trigger the problematic memory management sequence. This flaw directly corresponds to CWE-704, which addresses insufficient error handling during memory allocation operations, and represents a classic example of improper resource management in software development practices.
The operational impact of CVE-2011-0064 extends beyond simple application crashes to potentially enable remote code execution in certain circumstances. Attackers can craft malicious OpenType font files that, when processed by vulnerable applications, will trigger the memory allocation failure condition. This results in NULL pointer dereferences that cause application instability and can lead to system crashes. More concerning is the potential for exploitation to escalate to arbitrary code execution, particularly when the corrupted memory state allows for controlled data manipulation. The vulnerability affects widely deployed software components, making it particularly dangerous in environments where users may encounter untrusted font content through web browsing, document processing, or other applications that utilize HarfBuzz for text rendering.
Mitigation strategies for this vulnerability require immediate patching of affected software components to ensure proper memory allocation validation is implemented. Organizations should prioritize updating Pango, Firefox, and other affected applications to versions containing the patched hb_buffer_ensure function that properly validates memory reallocation outcomes. Additionally, system administrators should implement font validation policies that restrict the processing of untrusted font files, particularly in environments where users may encounter potentially malicious content. The remediation approach aligns with ATT&CK technique T1203, which addresses the exploitation of memory corruption vulnerabilities, and emphasizes the importance of defensive programming practices including proper error handling and resource management. Organizations should also consider implementing application sandboxing and input validation measures to limit the potential impact of successful exploitation attempts, while monitoring for indicators of compromise related to font processing anomalies.