CVE-2000-0974 in Privacy Guard
Summary
by MITRE
GnuPG (gpg) 1.0.3 does not properly check all signatures of a file containing multiple documents, which allows an attacker to modify contents of all documents but the first without detection.
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Analysis
by VulDB Data Team • 06/25/2021
The vulnerability identified as CVE-2000-0974 affects GnuPG version 1.0.3 and represents a critical flaw in the cryptographic signature verification process. This issue stems from insufficient validation mechanisms within the software's handling of multi-document files, creating a significant security weakness that undermines the integrity protection mechanisms designed to ensure document authenticity. The flaw specifically manifests when GnuPG processes files containing multiple documents, where the software fails to properly validate signatures for all components within the file structure.
This technical deficiency creates a scenario where an attacker can manipulate content across multiple documents while maintaining the appearance of valid signatures for the first document. The vulnerability operates at the core of GnuPG's signature verification algorithm, where the software incorrectly assumes that if the first document's signature validates correctly, all subsequent documents in the same file are also authentic. This assumption leads to a false sense of security and allows for undetected modification of data within the file structure. The flaw represents a classic case of incomplete input validation and inadequate cryptographic verification protocols, which can be categorized under CWE-295 - Improper Certificate Validation and CWE-311 - Missing Encryption of Sensitive Data.
The operational impact of this vulnerability extends beyond simple data integrity concerns to encompass serious security implications for any system relying on GnuPG for document authentication and verification. Organizations using affected versions of GnuPG may unknowingly process compromised files where only the first document appears legitimate while all others contain malicious or unauthorized modifications. This creates a dangerous environment where security controls fail silently, potentially allowing attackers to inject malicious code, alter critical information, or conduct data tampering operations without detection. The vulnerability particularly affects environments where GnuPG is used for software distribution, document signing, or secure communications where multi-document files are common.
Mitigation strategies for CVE-2000-0974 require immediate software updates to versions that properly implement signature validation for all documents within multi-document files. System administrators should conduct comprehensive vulnerability assessments to identify all instances of affected GnuPG versions and implement patch management procedures to ensure timely updates. Additionally, organizations should consider implementing supplementary verification mechanisms such as checksum validation, additional cryptographic signatures, or manual document verification processes for critical files. The ATT&CK framework categorizes this vulnerability under T1553 - Subvert Trust Controls, as it exploits the trust relationship between the cryptographic signature and the integrity of the entire document set. Security teams should also implement monitoring procedures to detect unusual file modification patterns that might indicate exploitation attempts, while maintaining proper audit trails for all cryptographic operations and signature verifications performed on sensitive documents.