CVE-2011-0433 in t1lib
Summary
by MITRE
Heap-based buffer overflow in the linetoken function in afmparse.c in t1lib, as used in teTeX 3.0.x, GNOME evince, and possibly other products, allows remote attackers to cause a denial of service (crash) and possibly execute arbitrary code via a DVI file containing a crafted Adobe Font Metrics (AFM) file, a different vulnerability than CVE-2010-2642.
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Analysis
by VulDB Data Team • 12/20/2021
The vulnerability identified as CVE-2011-0433 represents a critical heap-based buffer overflow flaw within the t1lib library's afmparse.c component, specifically within the linetoken function. This issue affects multiple widely-used software products including teTeX 3.0.x document processing systems, GNOME evince document viewers, and potentially other applications that rely on t1lib for font processing. The vulnerability stems from inadequate input validation when processing Adobe Font Metrics files, which are commonly embedded within DVI (Device Independent) document files used in typesetting systems. When a maliciously crafted AFM file is processed, the linetoken function fails to properly bounds-check memory allocations, creating a condition where attacker-controlled data can overwrite adjacent heap memory regions.
The technical exploitation of this vulnerability occurs through the manipulation of DVI files that contain specially constructed AFM data, which triggers the buffer overflow during parsing operations. The heap-based nature of the vulnerability means that memory corruption occurs in the heap segment rather than on the stack, making the exploitation more complex but potentially more reliable for achieving arbitrary code execution. The flaw manifests as a classic buffer overflow where insufficient bounds checking allows a malicious actor to write beyond the allocated buffer boundaries, potentially overwriting critical heap metadata or adjacent memory structures. This vulnerability is classified under CWE-121 as a stack-based buffer overflow, though the heap-based variant presents unique exploitation characteristics that align with CWE-122 for heap-based buffer overflow conditions.
The operational impact of this vulnerability extends beyond simple denial of service scenarios to potentially enable remote code execution, making it particularly dangerous for applications that process untrusted document content. When exploited, the vulnerability can cause application crashes, system instability, and in some cases allow attackers to execute arbitrary code with the privileges of the affected application. This makes the vulnerability especially concerning for document processing applications, web browsers, and server applications that may encounter untrusted AFM files during normal operation. The vulnerability's presence in both teTeX and GNOME evince indicates a broad attack surface, as these applications are commonly used for document viewing and processing in both desktop and server environments.
Mitigation strategies for CVE-2011-0433 should focus on immediate patching of affected software components, particularly the t1lib library and applications that utilize it. Organizations should implement strict input validation for all AFM and DVI file processing, including the use of sandboxing techniques to isolate document processing operations. Network-based defenses should include content filtering to prevent the delivery of potentially malicious DVI files, while application-level protections should enforce memory safety mechanisms such as stack canaries and address space layout randomization. Additionally, the vulnerability demonstrates the importance of proper input validation and bounds checking in font processing libraries, aligning with ATT&CK technique T1059.007 for command and scripting interpreter usage. System administrators should monitor for exploitation attempts through intrusion detection systems and implement principle of least privilege for applications that process document content, as the vulnerability's exploitation pathway through DVI file processing aligns with ATT&CK tactic TA0005 for defense evasion and TA0002 for execution. Regular security assessments and vulnerability scanning should be conducted to identify other potentially affected components within the software supply chain that may rely on vulnerable versions of t1lib.