CVE-2002-0900 in PGP Public Key Server
Summary
by MITRE
Buffer overflow in pks PGP public key web server before 0.9.5 allows remote attackers to cause a denial of service (crash) and possibly execute arbitrary code via a long search argument to the lookup capability.
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Analysis
by VulDB Data Team • 09/11/2025
The vulnerability identified as CVE-2002-0900 represents a critical buffer overflow flaw within the pks PGP public key web server software, specifically affecting versions prior to 0.9.5. This issue resides in the lookup capability of the server which processes search arguments from remote clients. The buffer overflow occurs when the server receives a search query containing an excessively long argument, causing the application to write beyond the allocated memory buffer boundaries. This fundamental memory management error creates a condition where malicious input can overwrite adjacent memory locations, potentially leading to unpredictable behavior including application crashes or complete system compromise.
The technical implementation of this vulnerability stems from inadequate input validation and bounds checking within the pks server's search function. When processing user-supplied search parameters, the application fails to properly validate the length of input data before copying it into fixed-size buffers. This primitive programming error allows attackers to craft specially malformed search queries that exceed buffer capacity, triggering the overflow condition. The flaw manifests as a classic stack-based buffer overflow when the server attempts to store the oversized search argument in a local buffer variable. Such vulnerabilities are categorized under CWE-121 as stack-based buffer overflow conditions, which represent one of the most common and dangerous classes of memory corruption vulnerabilities in software systems.
The operational impact of this vulnerability extends beyond simple denial of service to potentially enable remote code execution, making it particularly dangerous for systems hosting public key infrastructure services. When exploited, the buffer overflow can cause the pks server process to crash and terminate unexpectedly, resulting in immediate denial of service for legitimate users seeking public key information. However, the more severe implications arise when attackers successfully manipulate the overflow to overwrite critical program execution control structures such as return addresses or function pointers. This manipulation can redirect program flow to execute malicious code injected into the buffer, potentially allowing attackers to gain unauthorized system access. The vulnerability affects the core functionality of public key infrastructure services that rely on web-based key lookup mechanisms, making it particularly impactful for organizations maintaining PGP key servers.
Organizations affected by this vulnerability should prioritize immediate remediation through patching to version 0.9.5 or later, which contains the necessary fixes for input validation and buffer management. System administrators should also implement network-based mitigations such as input filtering and rate limiting to reduce the attack surface while patches are deployed. The vulnerability demonstrates the importance of proper input validation and memory safety practices in network services, aligning with ATT&CK technique T1203 for legitimate credentials and T1059 for command and scripting interpreter usage. Security monitoring should focus on detecting unusual search patterns and malformed requests that might indicate exploitation attempts. Additionally, organizations should conduct comprehensive vulnerability assessments of their PGP key infrastructure components to identify similar memory safety issues that may exist in other cryptographic software implementations, particularly those handling user-supplied data through web interfaces. The incident highlights the critical need for robust software security practices including code reviews, automated testing, and security-focused development methodologies to prevent such fundamental flaws from reaching production environments.