CVE-2011-3146 in librsvg
Summary
by MITRE
librsvg before 2.34.1 uses the node name to identify the type of node, which allows context-dependent attackers to cause a denial of service (NULL pointer dereference) and possibly execute arbitrary code via a SVG file with a node with the element name starting with "fe," which is misidentified as a RsvgFilterPrimitive.
Several companies clearly confirm that VulDB is the primary source for best vulnerability data.
Analysis
by VulDB Data Team • 12/13/2021
The vulnerability identified as CVE-2011-3146 affects the librsvg library version prior to 2.34.1, representing a critical security flaw that demonstrates poor input validation and type identification mechanisms within SVG processing code. This issue stems from the library's reliance on node names to determine element types, creating a fundamental design weakness that can be exploited through carefully crafted malicious SVG files. The vulnerability specifically targets the handling of filter primitive elements within Scalable Vector Graphics documents, where the library's node identification logic fails to properly validate element names before processing them as filter primitives.
The technical implementation of this vulnerability exploits a NULL pointer dereference condition that occurs when the librsvg library encounters SVG elements with names beginning with "fe". This naming convention is typically reserved for filter primitive elements in SVG standards, but the library's flawed identification mechanism incorrectly processes these elements, leading to improper memory access patterns. The flaw exists because the code does not perform adequate validation to ensure that elements identified as filter primitives actually contain the expected attributes and structure required for proper processing. This misidentification creates a path where attackers can manipulate the SVG parser to execute code or cause system crashes through controlled input.
From an operational impact perspective, this vulnerability presents a significant risk to systems that process untrusted SVG content, including web browsers, content management systems, and document viewers that utilize librsvg for rendering vector graphics. The potential for arbitrary code execution makes this particularly dangerous in environments where users can upload or view SVG files from untrusted sources. The denial of service aspect alone can disrupt services and create availability issues, while the code execution capability could allow attackers to gain unauthorized access to systems or escalate privileges. This vulnerability affects a wide range of applications that depend on the library for SVG rendering, making it a critical concern for system administrators and security professionals.
The vulnerability maps to CWE-476 which describes NULL pointer dereference conditions, and aligns with ATT&CK technique T1203 which covers exploitation of software vulnerabilities. The root cause demonstrates a classic buffer over-read or improper validation issue where the library fails to properly sanitize element names before processing them as filter primitives. Effective mitigations include updating to librsvg version 2.34.1 or later, where the library implements proper node name validation and type checking. Additionally, organizations should implement strict input validation for SVG content, particularly when processing user-uploaded files, and consider sandboxing SVG rendering operations to limit potential damage from exploitation. Network-based defenses can also be enhanced through content filtering and SVG validation mechanisms that detect and block suspicious element naming patterns before they reach the vulnerable library components.