CVE-2018-17333 in libsvg2
Summary
by MITRE
An issue was discovered in libsvg2 through 2012-10-19. A stack-based buffer overflow in svgStringToLength in svg_types.c allows remote attackers to cause a denial of service (application crash) or possibly have unspecified other impact because sscanf is misused.
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Analysis
by VulDB Data Team • 03/26/2020
The vulnerability identified as CVE-2018-17333 resides within the libsvg2 library, a component commonly used for parsing and rendering scalable vector graphics files. This library, which was last updated on October 19, 2012, contains a critical stack-based buffer overflow flaw in the svgStringToLength function located within the svg_types.c source file. The issue stems from improper usage of the sscanf function, which is a standard C library function used for parsing formatted input strings. When processing SVG files containing specially crafted malformed input data, the function fails to properly validate input boundaries, creating an exploitable condition that can lead to unpredictable system behavior.
The technical exploitation of this vulnerability occurs through a stack-based buffer overflow scenario where malicious input data exceeds the allocated buffer space during string parsing operations. The misused sscanf function does not adequately check input length limits before copying data into fixed-size buffers on the stack. This particular flaw falls under CWE-121, which specifically addresses stack-based buffer overflow conditions, and represents a classic example of improper input validation in string handling functions. Attackers can leverage this vulnerability by crafting malicious SVG files that contain oversized numeric or string values in attributes that are processed by the svgStringToLength function, thereby triggering the buffer overflow condition.
The operational impact of CVE-2018-17333 extends beyond simple denial of service scenarios, though that represents the most immediate consequence. While the primary effect manifests as application crashes and system instability, the vulnerability could potentially enable more sophisticated attacks depending on the execution environment and memory layout. Remote attackers can exploit this weakness without requiring local access, making it particularly dangerous in web applications or services that process untrusted SVG content. The vulnerability affects systems that utilize libsvg2 for SVG file processing, including web browsers, graphic design applications, and document processing systems that incorporate this library. From an ATT&CK framework perspective, this vulnerability aligns with techniques involving buffer overflow exploitation and can be categorized under initial access and execution phases of an attack chain.
Mitigation strategies for CVE-2018-17333 should focus on immediate remediation through library updates or patches provided by the maintainers of libsvg2. Organizations should prioritize updating to versions that contain proper input validation and boundary checking mechanisms for the sscanf function usage. Additionally, implementing input sanitization measures at application level can provide defense-in-depth protection, including validating all SVG input data against expected formats and length constraints. Network-level protections such as web application firewalls and content filtering systems can help detect and block malicious SVG content before it reaches vulnerable applications. System administrators should also consider implementing application sandboxing and memory protection mechanisms like stack canaries and address space layout randomization to reduce the exploitability of such buffer overflow conditions. The vulnerability demonstrates the critical importance of maintaining up-to-date third-party libraries and implementing comprehensive input validation practices to prevent exploitation of legacy code vulnerabilities.