CVE-2011-2441 in Acrobat
Summary
by MITRE
Multiple stack-based buffer overflows in CoolType.dll in Adobe Reader and Acrobat 8.x before 8.3.1, 9.x before 9.4.6, and 10.x before 10.1.1 allow attackers to execute arbitrary code via unspecified vectors.
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Analysis
by VulDB Data Team • 11/20/2021
The vulnerability identified as CVE-2011-2441 represents a critical stack-based buffer overflow flaw within the CoolType.dll component of Adobe Reader and Acrobat software across multiple versions. This vulnerability resides in the font handling mechanism of the application, specifically within the CoolType rendering engine responsible for processing font files. The affected versions include Adobe Reader 8.x prior to 8.3.1, 9.x prior to 9.4.6, and 10.x prior to 10.1.1, indicating a widespread impact across the Adobe Acrobat ecosystem. The vulnerability stems from insufficient input validation when processing maliciously crafted font files, particularly those utilizing the TrueType font format that the CoolType.dll component processes. Attackers can exploit this flaw by crafting specially designed font files that trigger the buffer overflow condition when the vulnerable software attempts to render them. The stack-based nature of the overflow means that the attacker can overwrite return addresses and other critical stack data, potentially allowing for arbitrary code execution with the privileges of the affected user. This vulnerability aligns with CWE-121, which describes stack-based buffer overflow conditions where insufficient bounds checking allows attackers to overwrite adjacent stack memory. The exploitability of this vulnerability is significantly enhanced by the fact that Adobe Reader and Acrobat are widely deployed applications, making them attractive targets for attackers seeking to gain unauthorized access to systems. The operational impact of this vulnerability extends beyond simple code execution, as it can enable attackers to establish persistent access, escalate privileges, or deploy additional malware. The attack surface is particularly concerning because font files are commonly encountered in various document formats, including pdf files, making it possible for attackers to deliver malicious payloads through seemingly benign documents. This vulnerability also maps to several ATT&CK techniques including T1059 for command and script interpreter and T1068 for exploit for privilege escalation, as the successful exploitation could lead to elevated system access. The attack vector typically involves social engineering elements where users open malicious documents containing crafted font files, which then trigger the buffer overflow in the CoolType.dll component. The vulnerability demonstrates a classic example of how font rendering libraries can become attack surfaces, as the complex parsing requirements for font files often introduce numerous potential entry points for exploitation. Organizations using affected versions of Adobe Reader and Acrobat face significant risk of compromise, as the vulnerability can be exploited remotely through malicious documents without requiring any special privileges from the user. The remediation process requires immediate patching of the affected software versions, with Adobe releasing updates to address this specific buffer overflow vulnerability in their CoolType.dll component. Security administrators should prioritize this vulnerability in their patch management cycles due to its high severity and widespread exploitation potential. The vulnerability also highlights the importance of keeping third-party libraries updated, as the CoolType.dll component represents a critical dependency within the Adobe product suite that requires regular security maintenance.
The technical implementation of this vulnerability involves the manipulation of font data structures that are processed by the CoolType.dll module during document rendering. When Adobe Reader or Acrobat encounters a font file that triggers the buffer overflow condition, the software fails to properly validate the size of data being copied to stack buffers. This failure creates a condition where attacker-controlled data can overflow the allocated stack space, potentially overwriting critical program execution data. The vulnerability specifically affects the handling of certain font parameters within TrueType font files, particularly those involving glyph data or font metrics that exceed expected buffer sizes. The exploitation process typically requires precise control over the font file structure to ensure that the overflow occurs at a specific location within the stack memory. This precision makes the vulnerability suitable for reliable exploitation in targeted attacks. The vulnerability's classification under CWE-121 indicates that it involves a classic stack buffer overflow where the attacker can manipulate the program flow by overwriting return addresses and other stack-based control structures. The fact that this vulnerability affects multiple versions of Adobe's software suggests that it was likely introduced in the CoolType.dll component's architecture and persisted across various releases due to inadequate security testing during development. The exploitation of this vulnerability can result in complete system compromise, as the attacker can execute arbitrary code within the context of the Adobe Reader or Acrobat process, potentially leading to privilege escalation or lateral movement within the network. The vulnerability's impact is amplified by the widespread deployment of Adobe Reader and Acrobat across enterprise environments, making it a prime target for nation-state actors and sophisticated threat groups seeking to establish persistent access to organizational networks. Security professionals should monitor for indicators of compromise related to this vulnerability, including unusual network connections or process execution patterns that might indicate exploitation attempts. The vulnerability also demonstrates the importance of input validation in complex multimedia processing libraries, as font rendering requires extensive parsing of binary data structures that can introduce numerous potential attack vectors if not properly secured.