CVE-2012-4513 in Konqueror
Summary
by MITRE
khtml/imload/scaledimageplane.h in Konqueror in KDE 4.7.3 allows remote attackers to cause a denial of service (crash) and possibly read memory via large canvas dimensions, which leads to an unexpected sign extension and a heap-based buffer over-read.
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Analysis
by VulDB Data Team • 09/21/2024
The vulnerability identified as CVE-2012-4513 resides within the khtml/imload/scaledimageplane.h component of Konqueror web browser in the KDE 4.7.3 software stack. This flaw represents a critical security issue that affects the rendering engine's handling of image data, specifically when processing canvas dimensions that exceed normal operational parameters. The vulnerability operates through a sophisticated exploitation vector that leverages the inherent characteristics of signed integer arithmetic within the image processing pipeline.
The technical mechanism behind this vulnerability involves an unexpected sign extension that occurs when large canvas dimensions are processed by the scaled image plane component. When dimension values exceed the maximum positive value that can be represented in the signed integer type used internally, the sign bit gets extended, causing the value to become negative. This negative value then gets used as a buffer size parameter, leading to a heap-based buffer over-read condition. The flaw is particularly insidious because it requires the attacker to craft specific image data with deliberately large canvas dimensions that trigger this particular arithmetic behavior.
The operational impact of this vulnerability manifests as a remote denial of service condition that causes Konqueror to crash and terminate unexpectedly. This crash occurs when the browser attempts to render images with the maliciously crafted canvas dimensions, resulting in memory corruption that leads to application instability. Beyond the immediate denial of service, there exists a potential for memory disclosure, where the buffer over-read could expose sensitive information from adjacent memory locations, potentially including stack contents, heap data, or other process memory segments. This aspect elevates the vulnerability beyond simple availability impact to include confidentiality concerns.
This vulnerability maps directly to CWE-129, which describes improper validation of array indices, and CWE-190, which covers integer overflow or wraparound conditions. The attack pattern aligns with techniques described in the ATT&CK framework under T1499.004 for network denial of service and potentially T1552.001 for data hijacking through memory disclosure. The exploit requires remote code execution capabilities through web content delivery, making it particularly dangerous in web browsing environments where users may encounter maliciously crafted HTML or image content.
Mitigation strategies for this vulnerability include immediate patching of the KDE 4.7.3 installation to the latest available version that contains the fix for the integer overflow condition in the image processing component. Additionally, implementing strict input validation on canvas dimensions within web applications and browser extensions can help prevent exploitation. Network-level defenses such as web application firewalls should be configured to monitor for unusual image dimension parameters, and browser security policies should be enforced to limit the execution of untrusted web content with potentially malicious image data. Organizations should also consider implementing memory protection mechanisms such as address space layout randomization and stack canaries to reduce the effectiveness of potential exploitation attempts.