CVE-2015-3905 in t1utils
Summary
by MITRE
Buffer overflow in the set_cs_start function in t1disasm.c in t1utils before 1.39 allows remote attackers to cause a denial of service (crash) and possibly execute arbitrary code via a crafted font file.
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Analysis
by VulDB Data Team • 11/24/2024
The vulnerability identified as CVE-2015-3905 represents a critical buffer overflow flaw within the t1disasm component of the t1utils utility suite, specifically affecting versions prior to 1.39. This issue resides in the set_cs_start function located within the t1disasm.c source file, demonstrating a classic memory corruption vulnerability that can be exploited through maliciously crafted font files. The t1utils package is commonly used for handling Type 1 font files, which are widely employed in PostScript and PDF document processing systems across various operating environments.
The technical implementation of this vulnerability stems from inadequate input validation and bounds checking within the set_cs_start function. When processing font files, the function fails to properly validate the size of incoming data structures, allowing attackers to provide oversized input that exceeds the allocated buffer space. This buffer overflow condition occurs because the implementation does not perform sufficient boundary checks before copying data into fixed-size memory buffers, creating a scenario where adjacent memory regions can be overwritten. The flaw manifests when the disassembler processes malformed font data, particularly in the context of character set definitions within Type 1 font files, which are fundamental components used in document rendering and printing systems.
The operational impact of this vulnerability extends beyond simple denial of service to potentially enable remote code execution, making it a particularly dangerous security flaw. An attacker who successfully exploits this vulnerability could cause the targeted application to crash through controlled memory corruption, leading to service disruption and potential system instability. More critically, the buffer overflow could be leveraged to execute arbitrary code within the context of the running process, potentially allowing attackers to gain unauthorized access to systems processing font files. This risk is particularly significant in environments where font processing occurs automatically, such as web browsers handling PDF documents, print servers processing user submissions, or content management systems handling document uploads.
The exploitation of this vulnerability aligns with several ATT&CK techniques including T1203 (Exploitation for Execution) and T1499 (Endpoint Denial of Service), with the potential for privilege escalation depending on the execution context. From a CWE perspective, this represents a classic CWE-121: Stack-based Buffer Overflow, though it could also manifest as CWE-787: Out-of-bounds Write depending on the specific memory layout and exploitation vector. The vulnerability's impact is amplified by the widespread use of Type 1 fonts in enterprise document processing pipelines, making it an attractive target for attackers seeking to compromise systems through document-based attack vectors. Organizations using applications that process font files, particularly those in document management, printing, or web browsing environments, face significant risk from this vulnerability.
Mitigation strategies should focus on immediate patching of affected systems to upgrade to t1utils version 1.39 or later, which includes proper bounds checking and input validation. Additionally, implementing defensive measures such as restricting font file processing to trusted sources, employing sandboxing techniques for font handling components, and deploying network-based intrusion detection systems to monitor for exploitation attempts can provide layered protection. System administrators should also consider implementing principle of least privilege for applications that process font files, limiting the potential impact if exploitation occurs. Regular security assessments of document processing pipelines and font handling components should be conducted to identify similar vulnerabilities in other font processing utilities, as this type of memory corruption flaw is not uncommon in legacy font parsing code.