CVE-2006-7250 in OpenSSL
Summary
by MITRE
The mime_hdr_cmp function in crypto/asn1/asn_mime.c in OpenSSL 0.9.8t and earlier allows remote attackers to cause a denial of service (NULL pointer dereference and application crash) via a crafted S/MIME message.
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Analysis
by VulDB Data Team • 11/30/2021
The vulnerability described in CVE-2006-7250 represents a critical denial of service flaw within the OpenSSL cryptographic library that affects versions 0.9.8t and earlier. This issue specifically targets the mime_hdr_cmp function located in the crypto/asn1/asn_mime.c file, which is responsible for processing S/MIME messages within the cryptographic framework. The vulnerability arises from inadequate input validation and error handling within the S/MIME message parsing mechanism, creating a scenario where maliciously crafted S/MIME messages can trigger unexpected application behavior.
The technical implementation of this vulnerability stems from a NULL pointer dereference condition that occurs when the mime_hdr_cmp function processes malformed S/MIME content. When an attacker constructs a specially crafted S/MIME message with malformed header fields or corrupted data structures, the function fails to properly validate the input parameters before attempting to dereference pointers. This flaw falls under the category of improper input validation and can be classified as CWE-476, which specifically addresses NULL pointer dereference vulnerabilities. The function's inability to handle unexpected or malformed input gracefully results in the application crashing when it attempts to access memory locations that have not been properly initialized or allocated.
The operational impact of this vulnerability extends beyond simple service disruption, as it can be exploited by remote attackers without requiring authentication or privileged access. An attacker can simply send a crafted S/MIME message to any system running the vulnerable OpenSSL version to trigger the denial of service condition. This makes the vulnerability particularly dangerous in environments where systems process email messages or other S/MIME encoded communications, as the attack can be executed silently and without detection. The crash typically results in immediate application termination, forcing system administrators to restart services and potentially disrupting legitimate communications.
From an adversarial perspective, this vulnerability aligns with ATT&CK technique T1499.004, which covers network denial of service attacks, and specifically targets the availability aspect of the CIA triad. The attack vector represents a classic remote code execution path through input manipulation, where the attacker leverages the application's failure to validate input integrity. The vulnerability demonstrates a fundamental security weakness in the cryptographic library's error handling mechanisms, where the system fails to implement proper defensive programming practices. Organizations using vulnerable OpenSSL versions face significant risk as this flaw can be exploited by automated scanning tools or targeted attackers to systematically disrupt services.
Mitigation strategies for CVE-2006-7250 primarily focus on immediate version upgrades to OpenSSL 0.9.8u or later, which contain the necessary patches to address the NULL pointer dereference issue. System administrators should implement comprehensive patch management procedures to ensure all affected systems receive updates promptly. Additionally, network administrators can implement message filtering rules at email gateways to detect and block suspicious S/MIME content, though this approach provides only partial protection. The vulnerability highlights the importance of input validation and proper error handling in cryptographic libraries, emphasizing that security-critical components must implement robust defensive measures against malformed input. Organizations should also consider implementing intrusion detection systems that can identify unusual application crash patterns, as these may indicate exploitation attempts. The incident underscores the critical need for continuous security monitoring and regular vulnerability assessments to identify and remediate similar issues before they can be exploited by malicious actors.