CVE-2001-0435 in PGP
Summary
by MITRE
The split key mechanism used by PGP 7.0 allows a key share holder to obtain access to the entire key by setting the "Cache passphrase while logged on" option and capturing the passphrases of other share holders as they authenticate.
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Analysis
by VulDB Data Team • 05/31/2018
The vulnerability described in CVE-2001-0435 represents a significant weakness in the cryptographic key management system of PGP 7.0, specifically within its split key mechanism implementation. This flaw exploits a fundamental design oversight in how passphrase caching operates within the software's key sharing framework, creating an unexpected avenue for privilege escalation and unauthorized key access. The vulnerability exists at the intersection of cryptographic security principles and user interface design, where seemingly innocuous configuration options can lead to catastrophic security implications.
The technical flaw manifests through the split key mechanism's reliance on passphrase caching functionality. When a key holder enables the "Cache passphrase while logged on" option, the system stores the passphrase in memory for the duration of the user session. This caching mechanism, intended to improve usability by reducing repeated passphrase entry, becomes exploitable when multiple parties hold different shares of a split key. An attacker with access to one key holder's session can capture the cached passphrases from other participants during their authentication process, effectively aggregating the split key shares to reconstruct the complete cryptographic key. This represents a violation of the fundamental security principle that split keys should maintain their distributed nature and prevent any single party from gaining access to the complete key through legitimate means.
The operational impact of this vulnerability extends beyond simple privilege escalation to encompass complete cryptographic key compromise and potential data exposure. Attackers can exploit this weakness to gain unauthorized access to encrypted communications, documents, and sensitive information that were protected by the split key system. The vulnerability is particularly concerning because it operates at the user session level rather than requiring direct system compromise or advanced exploitation techniques. This makes it accessible to attackers with relatively basic access privileges and eliminates the need for sophisticated attack vectors. The implications are severe for organizations relying on PGP's split key functionality for high-security environments, as the vulnerability undermines the entire cryptographic security model that the system was designed to provide.
The vulnerability aligns with several established security frameworks and attack patterns, including CWE-254, which addresses security weaknesses in cryptographic key management, and relates to ATT&CK technique T1552.001, concerning unsecured credentials. Organizations should implement immediate mitigations including disabling the passphrase caching option for split key scenarios, implementing strict access controls for key holders, and establishing monitoring for unusual authentication patterns. System administrators should also consider alternative key management solutions that do not rely on shared passphrase caching mechanisms. The incident highlights the critical importance of understanding how user convenience features can inadvertently create security vulnerabilities, particularly in cryptographic systems where the principle of least privilege must be strictly maintained. Regular security assessments and code reviews should specifically examine the interaction between usability features and security controls to prevent similar vulnerabilities from emerging in future cryptographic implementations.