CVE-1999-0892 in Communicator
Summary
by MITRE
Buffer overflow in Netscape Communicator before 4.7 via a dynamic font whose length field is less than the size of the font.
Once again VulDB remains the best source for vulnerability data.
Analysis
by VulDB Data Team • 04/20/2026
The vulnerability described in CVE-1999-0892 represents a classic buffer overflow condition that affected Netscape Communicator versions prior to 4.7. This security flaw emerged from improper handling of dynamic font data within the web browser's rendering engine, specifically when processing font information that contained malformed length fields. The issue occurred during the parsing of font resources that were dynamically loaded into the browser environment, creating a scenario where attacker-controlled input could potentially overwrite adjacent memory regions.
The technical implementation of this vulnerability stems from insufficient input validation within Netscape's font processing routines. When the browser encountered a dynamic font with a length field that was smaller than the actual font size, the parsing code would proceed to copy font data beyond the allocated buffer boundaries. This condition falls under the Common Weakness Enumeration category CWE-121, which deals with stack-based buffer overflow vulnerabilities, and more specifically aligns with CWE-125, representing out-of-bounds read conditions. The flaw exploited the lack of proper bounds checking when determining how much data to copy from the font resource into internal memory buffers.
From an operational perspective, this vulnerability presented significant risks to users of Netscape Communicator 4.6 and earlier versions. An attacker could craft malicious web pages containing specially formatted font data that would trigger the buffer overflow when the browser attempted to render the page. The successful exploitation of this vulnerability could lead to arbitrary code execution on the victim's system, potentially allowing attackers to gain complete control over the affected machine. This type of vulnerability would have been particularly dangerous in the late 1990s when web browsers were becoming primary attack vectors for malware distribution and system compromise.
The impact of this vulnerability extends beyond simple code execution, as it demonstrates the broader category of memory corruption flaws that have plagued software applications for decades. Modern threat actors and security researchers would classify this issue under the MITRE ATT&CK framework within the technique T1059.007, which covers command and script interpreter execution, and potentially T1203, which involves exploitation for privilege escalation. Organizations using vulnerable versions of Netscape Communicator would have been particularly susceptible to targeted attacks, as the buffer overflow could be leveraged to bypass security mechanisms and establish persistent access to compromised systems.
The remediation for this vulnerability required immediate patching of the Netscape Communicator browser through the release of version 4.7, which included proper bounds checking and input validation for font data processing. Security professionals would recommend that organizations immediately upgrade to patched versions and implement network monitoring to detect attempts to exploit this vulnerability. Additionally, browser vendors would later incorporate more robust memory safety mechanisms and improved input validation practices to prevent similar issues from occurring in future software releases, aligning with industry best practices for secure coding and vulnerability management.