CVE-2001-0071 in GnuPG
Summary
by MITRE
gpg (aka GnuPG) 1.0.4 and other versions does not properly verify detached signatures, which allows attackers to modify the contents of a file without detection.
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Analysis
by VulDB Data Team • 06/25/2021
The vulnerability identified as CVE-2001-0071 affects GnuPG versions 1.0.4 and earlier, specifically targeting the cryptographic signature verification process. This flaw represents a critical weakness in the integrity protection mechanisms that GnuPG employs to ensure document authenticity and tamper resistance. The vulnerability stems from insufficient validation of detached signatures, which are commonly used in digital document verification and software distribution scenarios where signature files are separate from the signed content.
The technical implementation flaw occurs within GnuPG's signature verification routine where the system fails to properly validate the relationship between the detached signature and the actual file content. This weakness allows an attacker to substitute a valid signature with a modified signature that appears authentic to the verification process. The vulnerability specifically impacts the signature verification algorithm's ability to detect when the signed content has been altered, creating a window where malicious modifications can occur without being detected by the recipient's verification process. This represents a fundamental breakdown in the cryptographic trust model that GnuPG is designed to maintain.
The operational impact of this vulnerability extends beyond simple document integrity concerns to encompass broader security implications for software distribution, secure communications, and digital identity verification systems. Attackers can exploit this flaw to modify files such as software packages, configuration documents, or cryptographic keys while maintaining the appearance of valid signatures. This capability undermines the core security objectives of public key cryptography and can lead to successful man-in-the-middle attacks, supply chain compromises, and unauthorized system access. The vulnerability particularly affects systems relying on GnuPG for software verification, email encryption, and secure file transfer protocols where signature integrity is paramount.
This vulnerability aligns with CWE-347, which addresses improper verification of cryptographic signatures, and corresponds to techniques described in the MITRE ATT&CK framework under T1556.004 for credential access through signature validation bypass. The flaw demonstrates a classic cryptographic weakness where the system's trust model is compromised through insufficient validation controls. Organizations using vulnerable versions of GnuPG should immediately implement patch management procedures to upgrade to versions that properly address signature verification. Additionally, system administrators should conduct comprehensive audits of all cryptographic verification processes and implement additional integrity checking mechanisms such as hash verification alongside signature validation to provide defense-in-depth protection against similar vulnerabilities.