CVE-2011-1554 in Xpdf
Summary
by MITRE
Off-by-one error 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 read, integer overflow, and invalid pointer dereference, a different vulnerability than CVE-2011-0764.
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Analysis
by VulDB Data Team • 12/28/2024
The vulnerability identified as CVE-2011-1554 represents a critical off-by-one error within the t1lib library version 5.1.2 and earlier implementations. This flaw specifically affects PDF processing systems that utilize Type 1 font handling capabilities, including Xpdf versions prior to 3.02pl6, teTeX, and numerous other software products that depend on t1lib for font rendering operations. The vulnerability stems from inadequate bounds checking during the processing of Type 1 font data within PDF documents, creating a scenario where malformed input can trigger cascading memory corruption issues.
The technical exploitation of this vulnerability involves a sophisticated sequence of memory manipulation errors that begin with an invalid memory read operation. When a PDF document contains a specially crafted Type 1 font, the t1lib library fails to properly validate the font data structure, leading to an integer overflow condition that subsequently causes an invalid pointer dereference. This chain of failures creates a situation where the application attempts to access memory locations that are either uninitialized, freed, or otherwise inaccessible, resulting in immediate application termination and denial of service. The vulnerability operates at the intersection of multiple CWE categories including CWE-125 Out-of-bounds Read, CWE-190 Integer Overflow or Wraparound, and CWE-476 NULL Pointer Dereference, making it particularly dangerous in the context of document processing applications.
The operational impact of CVE-2011-1554 extends beyond simple service disruption to potentially enable more sophisticated attack vectors within the broader ATT&CK framework. While the primary effect manifests as denial of service, the underlying memory corruption vulnerabilities create opportunities for remote code execution in systems where the application process can be manipulated to leverage the corrupted memory state. This vulnerability particularly affects content management systems, email servers, and web applications that process untrusted PDF documents, as attackers can craft malicious documents that will crash these systems when processed. The vulnerability's persistence across multiple software implementations indicates a fundamental flaw in the font processing pipeline that requires comprehensive patching across affected ecosystems.
Mitigation strategies for CVE-2011-1554 must address both immediate remediation and long-term architectural improvements. The primary recommendation involves upgrading all affected software components to versions that include patched t1lib libraries, with particular attention to Xpdf 3.02pl6 and later versions, as well as ensuring that teTeX and other dependent systems receive appropriate updates. Organizations should implement strict input validation measures that filter or sanitize PDF documents before processing, particularly focusing on Type 1 font data within documents. Network-level defenses can include content filtering solutions that identify and block PDF documents containing suspicious font structures, while application-level protections should incorporate memory safety mechanisms such as stack canaries and address space layout randomization. Additionally, implementing proper error handling and graceful degradation mechanisms can help prevent complete application crashes, though these measures do not address the root cause of the vulnerability. The remediation process should also include comprehensive testing of updated systems to ensure that the patch does not introduce regressions in legitimate PDF processing functionality while maintaining robust protection against similar vulnerabilities in the future.