CVE-2017-16899 in Xfig
Summary
by MITRE
An array index error in the fig2dev program in Xfig 3.2.6a allows remote attackers to cause a denial-of-service attack or information disclosure with a maliciously crafted Fig format file, related to a negative font value in dev/gentikz.c, and the read_textobject functions in read.c and read1_3.c.
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Analysis
by VulDB Data Team • 01/11/2023
The vulnerability identified as CVE-2017-16899 represents a critical array index error within the fig2dev component of Xfig version 3.2.6a, a widely used vector graphics editor and drawing tool. This flaw exists in the processing of Fig format files, which are commonly used for exchanging vector graphics between different applications. The vulnerability specifically manifests in the dev/gentikz.c file where negative font value handling occurs, combined with issues in the read_textobject functions located in read.c and read1_3.c. The flaw stems from inadequate input validation and bounds checking when parsing font-related parameters within Fig format files, creating a condition where maliciously crafted input can trigger unexpected behavior in the application's memory management systems.
The technical nature of this vulnerability places it squarely within the category of buffer over-read conditions and improper input validation, which aligns with CWE-129 and CWE-704 classifications. When a malicious Fig file containing negative font values is processed by fig2dev, the application attempts to access array elements using invalid indices, leading to unpredictable behavior that can result in either program termination or memory disclosure. The vulnerability's remote exploitability means that attackers can trigger the flaw without requiring local access, making it particularly dangerous in networked environments where users might unknowingly open or process maliciously crafted graphics files. This represents a classic example of how input sanitization failures in graphics processing software can create security risks that extend beyond simple application crashes.
The operational impact of CVE-2017-16899 is significant across multiple threat scenarios, particularly in environments where users regularly exchange vector graphics files or where automated processing systems handle Fig format files. The vulnerability can be exploited to cause denial-of-service conditions that disrupt legitimate user activities, potentially leading to complete application crashes or system unresponsiveness. Additionally, the information disclosure aspect of this vulnerability poses serious risks where sensitive memory contents might be exposed to attackers, potentially revealing system configuration details or other confidential information. The attack surface extends to any system running Xfig or applications that utilize fig2dev for format conversion, including servers processing user uploads, collaborative design environments, and automated graphic generation systems.
Mitigation strategies for this vulnerability require immediate patching of affected Xfig installations to version 3.2.7 or later, which contains the necessary fixes for the array index error. System administrators should implement strict file validation policies for Fig format files, particularly when processing user-generated content or files from untrusted sources. The principle of least privilege should be enforced when running fig2dev in automated environments, limiting the potential impact of successful exploitation. Network segmentation and file filtering mechanisms can help prevent malicious Fig files from reaching systems that process them, while regular security audits should verify that no outdated versions remain in production environments. From an ATT&CK perspective, this vulnerability maps to T1203 (Exploitation for Client Execution) and T1059 (Command and Scripting Interpreter) as attackers could leverage the denial-of-service capability to disrupt operations or potentially escalate privileges through related system weaknesses. Organizations should also consider implementing sandboxing techniques for graphics file processing to contain potential exploitation attempts and reduce the attack surface of vulnerable applications.