CVE-2006-3746 in GnuPG
Summary
by MITRE
Integer overflow in parse_comment in GnuPG (gpg) 1.4.4 allows remote attackers to cause a denial of service (segmentation fault) via a crafted message.
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Analysis
by VulDB Data Team • 06/18/2025
The vulnerability identified as CVE-2006-3746 represents a critical integer overflow flaw within the GNU Privacy Guard implementation that affects version 1.4.4 of the gpg utility. This vulnerability specifically resides in the parse_comment function, which is responsible for processing comment fields within OpenPGP messages. The integer overflow occurs when the application processes malformed or crafted comment data that exceeds the maximum value that can be represented by the integer data type used in the parsing routine. When this overflow condition is triggered, it results in unpredictable memory behavior that ultimately leads to a segmentation fault during program execution. The vulnerability is particularly concerning because it can be exploited remotely through the processing of maliciously crafted OpenPGP messages without requiring any authentication or privileged access.
The technical nature of this vulnerability aligns with CWE-190, which specifically addresses integer overflow conditions in software implementations. This flaw demonstrates how improper input validation and inadequate bounds checking in cryptographic software can create exploitable conditions that compromise system stability. The parse_comment function in GnuPG operates under the assumption that comment lengths will remain within reasonable bounds, but when faced with crafted input that triggers integer overflow, the application fails to handle the exceptional condition gracefully. The overflow causes the program to attempt memory operations with invalid addresses, leading to the segmentation fault that terminates the process. This type of vulnerability falls under the ATT&CK technique T1499.004, which covers "File and Directory Permissions Modification" through denial of service attacks that disrupt legitimate system operations.
The operational impact of CVE-2006-3746 extends beyond simple service disruption as it can be leveraged by attackers to create persistent denial of service conditions within environments that rely on GnuPG for secure communications. Systems that process incoming encrypted messages, such as email servers, automated key management systems, or any infrastructure that utilizes GnuPG for signature verification, become vulnerable to this attack vector. The remote exploitation capability means that an attacker can trigger the vulnerability from anywhere on the network without requiring physical access or local privileges. This makes the vulnerability particularly dangerous in environments where GnuPG is used to process messages from untrusted sources, such as public email systems, automated security alert processing, or any application that accepts OpenPGP formatted data from external parties. The segmentation fault resulting from this vulnerability can cause cascading failures in systems that depend on continuous GnuPG service availability.
Mitigation strategies for CVE-2006-3746 require immediate patching of affected GnuPG installations to version 1.4.5 or later, where the integer overflow has been corrected through proper input validation and bounds checking. Organizations should implement network segmentation and access controls to limit exposure of systems running vulnerable versions of GnuPG, particularly those processing external messages. Input sanitization measures should be enhanced to validate all comment fields in OpenPGP messages before processing, ensuring that length parameters remain within acceptable ranges. Security monitoring should be implemented to detect unusual segmentation fault patterns or service disruptions that may indicate exploitation attempts. Additionally, system administrators should conduct comprehensive vulnerability assessments to identify all instances of GnuPG 1.4.4 or earlier versions within their infrastructure, as the vulnerability can be exploited through various attack vectors including email processing, automated key verification systems, and any application that integrates with GnuPG for cryptographic operations. The patch for this vulnerability specifically addresses the integer overflow condition in the parse_comment function by implementing proper bounds checking and ensuring that comment length parameters are validated against maximum integer limits before being used in memory allocation operations.