CVE-1999-0853 in Netscape
Summary
by MITRE
Buffer overflow in Netscape Enterprise Server and Netscape FastTrack Server allows remote attackers to gain privileges via the HTTP Basic Authentication procedure.
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Analysis
by VulDB Data Team • 10/22/2025
The vulnerability identified as CVE-1999-0853 represents a critical buffer overflow flaw affecting Netscape Enterprise Server and Netscape FastTrack Server versions from 2.0 through 3.0. This security weakness resides within the HTTP Basic Authentication handling mechanism, specifically when processing authorization headers sent by clients. The flaw stems from inadequate input validation and bounds checking during the parsing of authentication credentials, creating an exploitable condition where maliciously crafted HTTP requests can trigger memory corruption. The vulnerability operates under CWE-121, which categorizes buffer overflow conditions where insufficient bounds checking allows attackers to overwrite adjacent memory locations. This type of vulnerability falls within the ATT&CK framework under T1072 for Application Deployment, as it exploits server-side application behavior to achieve privilege escalation.
The technical implementation of this buffer overflow occurs when the server processes HTTP Basic Authentication headers containing excessively long username or password values. The authentication parsing routine fails to properly validate the length of incoming data before copying it into fixed-size buffers, allowing attackers to overflow the allocated memory space and potentially overwrite critical program variables, return addresses, or other sensitive data structures. When the server attempts to process the malformed authentication request, the overflow can cause unpredictable behavior including program crashes, memory corruption, or more dangerously, the ability to execute arbitrary code with elevated privileges. The vulnerability specifically impacts the authentication subsystem, making it particularly dangerous as it directly targets the mechanism used to verify user identities and control access to server resources.
The operational impact of CVE-1999-0853 extends beyond simple service disruption to encompass full system compromise capabilities. Remote attackers can leverage this vulnerability to execute arbitrary code on affected servers, potentially gaining root or administrator privileges depending on the server configuration and execution context. This privilege escalation capability enables attackers to access sensitive data, modify server configurations, install malicious software, or establish persistent access points within the network infrastructure. The vulnerability affects enterprise web servers that rely on HTTP Basic Authentication for access control, making it particularly dangerous in corporate environments where these servers often host critical applications and sensitive information. The attack vector requires only a network connection to the vulnerable server and does not require authentication, making it easily exploitable by remote threat actors.
Mitigation strategies for CVE-1999-0853 should prioritize immediate patching of affected server versions, as Netscape released security updates specifically addressing this buffer overflow condition. Organizations should implement network segmentation and access controls to limit exposure of vulnerable servers to untrusted networks. The implementation of intrusion detection systems can help identify suspicious HTTP requests containing malformed authentication headers that may indicate exploitation attempts. Additionally, administrators should disable HTTP Basic Authentication where possible and implement alternative authentication mechanisms such as digest authentication or SSL client certificates. Security monitoring should include regular vulnerability scanning to identify unpatched systems and ensure that all server components are updated to versions that contain proper bounds checking and input validation routines. The vulnerability serves as a classic example of why input validation and memory safety practices are fundamental to secure application development, particularly in server-side applications handling user-provided data.