CVE-2016-9082 in Cairo
Summary
by MITRE
Integer overflow in the write_png function in cairo 1.14.6 allows remote attackers to cause a denial of service (invalid pointer dereference) via a large svg file.
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Analysis
by VulDB Data Team • 08/11/2020
The vulnerability identified as CVE-2016-9082 represents a critical integer overflow flaw within the cairo graphics library version 1.14.6 specifically affecting the write_png function. This issue arises when processing specially crafted svg files that contain excessive dimensions or parameters, leading to a scenario where integer arithmetic operations exceed their maximum representable values. The flaw manifests as an integer overflow during the calculation of memory allocation requirements for PNG output, which subsequently results in invalid pointer dereference conditions during the rendering process. Such vulnerabilities fall under the CWE-190 category of integer overflow, where the overflow occurs during arithmetic operations that should have been bounded by safe integer limits. The attack vector involves remote exploitation through the processing of malicious svg files that are then converted to png format, making this particularly concerning for web applications and systems that handle user-uploaded graphics content.
The operational impact of this vulnerability extends beyond simple denial of service conditions, as it creates a potential pathway for more sophisticated attacks within systems that rely on cairo for graphics processing. When the integer overflow occurs in the write_png function, the resulting memory allocation calculations produce values that are either negative or exceed the maximum bounds of the integer type, leading to unpredictable behavior including crashes, memory corruption, or potentially exploitable conditions. Systems utilizing cairo for rendering operations across web browsers, graphic design applications, or server-side image processing are particularly at risk when handling untrusted svg input. The vulnerability demonstrates how seemingly benign graphics processing operations can become attack surfaces when proper input validation and integer boundary checks are absent from critical code paths. This flaw aligns with ATT&CK technique T1203 by creating opportunities for process manipulation through memory corruption, while also representing a classic example of improper input validation that can lead to broader system compromise.
Mitigation strategies for CVE-2016-9082 should focus on immediate patching of affected cairo library versions to 1.14.8 or later, which contains the necessary fixes for integer overflow protection in the write_png function. Organizations should implement comprehensive input validation for all svg file processing, including size and dimension limits that prevent excessive values from being processed. Network segmentation and application firewalls can help limit exposure by restricting access to graphics processing endpoints. Additionally, deploying automated monitoring systems that detect unusual memory allocation patterns or process crashes during image conversion can provide early warning of exploitation attempts. The fix implemented in subsequent cairo releases typically involves adding explicit bounds checking and overflow detection mechanisms before any memory allocation occurs, ensuring that integer calculations remain within safe operational limits. System administrators should also consider implementing sandboxing techniques for graphics processing operations, isolating vulnerable applications from critical system resources to limit potential damage from successful exploitation attempts. Organizations maintaining legacy systems without immediate patch availability should consider implementing strict svg file validation policies that reject files exceeding predefined safe dimensions and complexity thresholds to reduce attack surface exposure.