CVE-2011-1553 in Xpdf
Summary
by MITRE
Use-after-free vulnerability in t1lib 5.1.2 and earlier, as used in Xpdf before 3.02pl6, teTeX, and other products, allows remote attackers to cause a denial of service (application crash) via a PDF document containing a crafted Type 1 font that triggers an invalid memory write, a different vulnerability than CVE-2011-0764.
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Analysis
by VulDB Data Team • 12/28/2024
The vulnerability identified as CVE-2011-1553 represents a critical use-after-free condition within the t1lib library version 5.1.2 and earlier implementations. This flaw manifests when processing PDF documents containing specially crafted Type 1 fonts that trigger invalid memory write operations. The vulnerability affects multiple software products including Xpdf versions prior to 3.02pl6, teTeX, and other applications that rely on t1lib for font handling. The underlying issue stems from improper memory management where freed memory blocks are still referenced or accessed by subsequent operations, creating a scenario where the application attempts to write to memory that has already been deallocated. This type of vulnerability falls under CWE-416, which specifically addresses use-after-free conditions, and represents a fundamental memory safety issue that can lead to unpredictable behavior and system instability.
The operational impact of this vulnerability extends beyond simple denial of service to potentially enable more sophisticated attacks depending on the execution environment. When a malicious PDF document triggers the vulnerable code path, the application crashes due to attempting to write to freed memory locations, resulting in a complete service interruption. The attack vector requires remote execution since an attacker can deliver the malicious PDF document through web browsers, email attachments, or any application that processes PDF files using the affected software components. This vulnerability is particularly concerning in environments where PDF processing is automated or where users frequently open untrusted documents, as it can be exploited without user interaction beyond opening the malicious file. The specific nature of the flaw means that exploitation does not require complex payload delivery mechanisms but rather relies on the inherent memory management error within the font processing subsystem.
Security professionals should understand that this vulnerability represents a classic example of how font processing libraries can introduce critical stability issues in document rendering applications. The flaw demonstrates the importance of proper memory management practices in font handling code and highlights the risks associated with legacy library versions that may not have received adequate security updates. Organizations using affected software should prioritize immediate patching or mitigation strategies, as the vulnerability has been classified with significant severity due to its potential for remote exploitation and the widespread use of the affected components. The vulnerability also aligns with ATT&CK technique T1203, which covers exploitation of remote services through memory corruption vulnerabilities. The remediation approach typically involves updating to patched versions of the affected software or implementing additional input validation measures to prevent processing of malformed font data, though the most effective solution remains the deployment of security updates that address the underlying use-after-free condition in t1lib.
The broader implications of CVE-2011-1553 extend to the security practices of software vendors and the importance of maintaining up-to-date dependencies. This vulnerability underscores how seemingly isolated library issues can affect entire ecosystems of applications that depend on them, making dependency management a critical aspect of software security. The flaw also illustrates the ongoing challenges in maintaining memory safety in legacy codebases where modern security practices may not have been fully implemented. Organizations should implement comprehensive vulnerability management programs that include regular dependency audits and automated patch deployment to prevent exploitation of similar issues in the future. The vulnerability serves as a reminder that font processing, while often considered a minor component of document rendering, can represent a significant attack surface that requires careful security consideration and regular maintenance to ensure proper memory handling and prevent exploitation through memory corruption techniques.