CVE-2013-4402 in GnuPG
Summary
by MITRE
The compressed packet parser in GnuPG 1.4.x before 1.4.15 and 2.0.x before 2.0.22 allows remote attackers to cause a denial of service (infinite recursion) via a crafted OpenPGP message.
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Analysis
by VulDB Data Team • 05/26/2021
The vulnerability identified as CVE-2013-4402 represents a critical denial of service flaw within GnuPG's compressed packet parsing functionality. This issue affects GnuPG versions 1.4.x prior to 1.4.15 and 2.0.x prior to 2.0.22, exposing systems that rely on OpenPGP message processing to potential disruption. The flaw manifests through improper handling of crafted OpenPGP messages that contain maliciously constructed compressed packet structures designed to trigger infinite recursion during parsing operations.
The technical root cause of this vulnerability lies in the insufficient validation and recursion depth checking within GnuPG's packet parser implementation. When processing compressed packets, the software fails to properly monitor or limit recursive parsing operations, allowing attackers to construct specially formatted OpenPGP messages that cause the parser to enter infinite recursive loops. This occurs because the compressed packet structure contains references to itself or creates circular dependencies that the parser cannot resolve without explicit recursion limits. The vulnerability specifically targets the decompression and parsing stages of OpenPGP message processing, where compressed data sections are handled.
The operational impact of CVE-2013-4402 extends beyond simple service disruption, as it can be exploited by remote attackers without authentication requirements. Systems processing OpenPGP messages, including email servers, file encryption systems, and any application that utilizes GnuPG for signature verification or message decryption, become vulnerable to this attack vector. The infinite recursion consumes system resources rapidly, potentially leading to complete system exhaustion, application crashes, or denial of service for legitimate users. This vulnerability aligns with CWE-674, which describes "Uncontrolled Recursion" as a weakness that can lead to resource exhaustion and system instability.
From an attack perspective, this vulnerability demonstrates characteristics consistent with the MITRE ATT&CK framework's privilege escalation and denial of service tactics. Attackers can leverage this flaw to systematically disrupt services that depend on GnuPG for secure communications, potentially affecting email infrastructure, secure file transfer systems, and cryptographic verification processes. The remote nature of the attack means that adversaries can exploit this vulnerability from anywhere on the network without requiring local access or credentials. Organizations using affected GnuPG versions face significant operational risks, particularly those relying on automated message processing or high-volume cryptographic operations.
Mitigation strategies for CVE-2013-4402 primarily involve immediate patching of affected GnuPG installations to versions 1.4.15 or 2.0.22 and later. System administrators should conduct comprehensive inventory checks to identify all systems running vulnerable GnuPG versions and implement remediation procedures promptly. Additionally, organizations should consider implementing network monitoring to detect unusual resource consumption patterns that might indicate exploitation attempts. Input validation controls and recursion depth monitoring should be enhanced in any custom applications that process OpenPGP messages, while security teams should review existing intrusion detection systems to ensure they can identify potential exploitation attempts. The vulnerability underscores the importance of proper input validation and recursive operation limits in cryptographic software implementations, particularly for protocols handling compressed data structures.