CVE-2006-4819 in Web Browser
Summary
by MITRE
Heap-based buffer overflow in Opera 9.0 and 9.01 allows remote attackers to execute arbitrary code via a long URL in a tag (long link address).
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Analysis
by VulDB Data Team • 04/24/2026
The vulnerability identified as CVE-2006-4819 represents a critical heap-based buffer overflow flaw affecting Opera web browsers version 9.0 and 9.01. This vulnerability resides in the browser's handling of URL parsing within HTML tag structures, specifically when processing excessively long link addresses. The flaw originates from insufficient input validation and bounds checking within Opera's HTML rendering engine, particularly in how it manages memory allocation for URL strings during tag processing. Attackers can exploit this weakness by crafting malicious URLs that exceed the allocated buffer size, causing a heap overflow condition that can be leveraged to execute arbitrary code on vulnerable systems. The vulnerability demonstrates characteristics consistent with CWE-121 Heap-based Buffer Overflow, where insufficient memory bounds checking allows attackers to overwrite adjacent heap memory regions. This type of vulnerability falls under the attack pattern category of CWE-770 Allocation of Resources Without Limits or Throttling, as the browser fails to properly limit the length of URL strings processed during HTML parsing operations.
The operational impact of this vulnerability extends beyond simple code execution to encompass complete system compromise when exploited successfully. Remote attackers can leverage this flaw to inject malicious code into the browser process, potentially leading to unauthorized access, data theft, or further system exploitation. The heap overflow condition creates predictable memory corruption patterns that attackers can manipulate through carefully crafted payload delivery mechanisms. When a user visits a malicious website containing a specially crafted long URL within an HTML tag, the browser's memory management routines fail to handle the excessive string length properly, resulting in memory corruption that can be directed to execute attacker-controlled code. This vulnerability particularly affects environments where Opera 9.0 and 9.01 remain in use, as these versions lack the memory safety improvements introduced in subsequent releases. The exploitation process aligns with ATT&CK technique T1059.007 Command and Scripting Interpreter: JavaScript, as attackers can leverage the overflow to execute JavaScript code that can then perform further malicious activities.
Mitigation strategies for CVE-2006-4819 focus primarily on immediate browser version upgrades to patched releases that address the underlying memory handling flaws. Organizations should implement comprehensive patch management processes to ensure all Opera installations are updated to versions that include proper bounds checking and memory allocation safeguards. Additional defensive measures include network-based filtering to block suspicious URL patterns and implementing web application firewalls that can detect and prevent exploitation attempts. Browser security configurations should be adjusted to disable unnecessary features that might exacerbate the vulnerability, such as automatic URL processing in HTML tags. The remediation approach must consider both immediate threat mitigation and long-term security posture improvements, including regular security assessments and vulnerability scanning to identify unpatched systems. Organizations should also consider implementing user education programs to raise awareness about visiting untrusted websites and the importance of keeping browser software updated. This vulnerability serves as a historical example of how memory safety issues in web browsers can create severe security risks, emphasizing the critical importance of proper input validation and bounds checking in security-sensitive applications.