CVE-2002-1091 in Netscape
Summary
by MITRE
Netscape 6.2.3 and earlier, and Mozilla 1.0.1, allow remote attackers to corrupt heap memory and execute arbitrary code via a GIF image with a zero width.
If you want to get best quality of vulnerability data, you may have to visit VulDB.
Analysis
by VulDB Data Team • 09/15/2025
This vulnerability affects Netscape 6.2.3 and earlier versions as well as Mozilla 1.0.1, representing a critical heap corruption issue that enables remote code execution through malformed GIF image handling. The flaw specifically manifests when the browser encounters a GIF image with a zero width parameter, which triggers improper memory management during image parsing operations. The vulnerability resides in the image rendering engine's failure to properly validate image dimensions before allocating heap memory for image data processing, creating a classic buffer overflow condition that can be exploited by malicious actors.
The technical implementation of this vulnerability demonstrates a clear violation of proper input validation principles and memory safety practices. When the browser processes a GIF image with zero width, the parsing routine fails to account for this edge case, leading to incorrect memory allocation calculations. This misallocation results in heap memory corruption that can be systematically manipulated to overwrite critical memory locations, ultimately allowing attackers to inject and execute arbitrary code with the privileges of the affected browser process. The vulnerability directly maps to CWE-121, heap-based buffer overflow, and CWE-787, out-of-bounds write, both of which are fundamental memory safety issues that have been extensively documented in cybersecurity literature.
From an operational perspective, this vulnerability presents a significant risk to users who browse the internet without up-to-date security patches, as it requires no user interaction beyond viewing a maliciously crafted GIF image. Attackers can deliver payloads through various vectors including web pages, email attachments, or even instant messaging applications that display images automatically. The exploitability factor is high due to the predictable nature of the memory corruption and the relatively simple attack vector that does not require complex social engineering or specialized tools. This vulnerability aligns with ATT&CK technique T1203, Exploitation for Client Execution, and T1059, Command and Scripting Interpreter, as it enables attackers to execute arbitrary commands through compromised browser processes.
The remediation strategy for this vulnerability requires immediate patching of affected browser versions, with users urged to upgrade to patched versions of Netscape or Mozilla browsers. Security administrators should implement network-based protections such as web application firewalls that can detect and block malformed GIF images before they reach client browsers. Additionally, browser hardening measures including disabling automatic image loading, implementing strict content security policies, and maintaining updated security patches across all browser installations provide layered defense against exploitation attempts. Organizations should also consider implementing monitoring solutions that can detect anomalous browser behavior patterns that may indicate exploitation attempts, particularly focusing on memory access violations and unexpected code execution within browser processes.