CVE-2005-1268 in HTTP Server
Summary
by MITRE
Off-by-one error in the mod_ssl Certificate Revocation List (CRL) verification callback in Apache, when configured to use a CRL, allows remote attackers to cause a denial of service (child process crash) via a CRL that causes a buffer overflow of one null byte.
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Analysis
by VulDB Data Team • 06/07/2019
The vulnerability identified as CVE-2005-1268 represents a critical off-by-one error within the mod_ssl module of the Apache HTTP Server that specifically affects Certificate Revocation List verification processes. This flaw exists in the SSL certificate validation callback mechanism where the software fails to properly handle buffer boundaries during CRL processing, creating a condition that can be exploited to trigger memory corruption. The vulnerability is particularly significant because it occurs during the certificate revocation verification phase, which is a fundamental security function that Apache performs when validating SSL certificates against known revoked certificates.
The technical implementation of this vulnerability stems from improper bounds checking in the CRL verification callback function that handles certificate revocation lists. When Apache processes a CRL file that contains maliciously crafted data, the off-by-one error causes the software to write one byte beyond the allocated buffer boundaries, resulting in a buffer overflow condition. This specific overflow affects only a single null byte, but due to the nature of memory layout and process management in the Apache server architecture, this seemingly minor overflow can cause the child process to crash and terminate unexpectedly. The flaw is particularly dangerous because it can be triggered remotely by any attacker who can submit a specially crafted CRL to the vulnerable Apache server.
The operational impact of CVE-2005-1268 extends beyond simple denial of service to potentially compromise the availability of web services that rely on SSL/TLS encryption. When a child process crashes due to this buffer overflow, Apache must restart the process to continue serving requests, leading to temporary service disruption and potential resource exhaustion if multiple attacks occur in quick succession. This vulnerability directly relates to CWE-121, which describes heap-based buffer overflow conditions, and can be mapped to ATT&CK technique T1499.100 which covers network denial of service attacks through resource exhaustion. The attack vector is particularly concerning because it requires no authentication and can be executed remotely, making it accessible to any attacker with network access to the vulnerable Apache server.
Mitigation strategies for this vulnerability should prioritize immediate patching of affected Apache installations, as the official Apache HTTP Server releases included fixes that properly address the buffer boundary checking issue in the mod_ssl module. System administrators should also implement monitoring solutions to detect unusual process restart patterns that might indicate exploitation attempts, while network security controls can be configured to restrict access to CRL distribution points from untrusted sources. Organizations should conduct comprehensive vulnerability assessments to identify all Apache installations that may be running affected versions of mod_ssl, particularly those configured to use CRL verification, and ensure that proper security updates are deployed across all environments to prevent potential exploitation that could lead to broader service disruption or compromise of SSL/TLS security assurances.