CVE-2005-0106 in libnet-ssleay-perl
Summary
by MITRE
ssleay.pm in libnet-ssleay-perl before 1.25 uses the /tmp/entropy file for entropy if a source is not set in the egd_path variable which allows local users to reduce the cryptographic strength of certain operations by modifying the file.
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Analysis
by VulDB Data Team • 06/13/2019
The vulnerability described in CVE-2005-0106 affects the libnet-ssleay-perl package version 1.25 and earlier, specifically within the ssleay.pm module that handles SSL/TLS cryptographic operations. This flaw represents a significant weakness in the entropy management system used by the Perl library for SSL connections, creating a pathway for local privilege escalation through cryptographic weakening. The issue stems from the module's fallback mechanism when no explicit entropy source is configured, defaulting to a predictable file location that can be manipulated by local users.
The technical flaw resides in the insecure default configuration where the system automatically falls back to using /tmp/entropy as a source of random numbers when the egd_path variable is not explicitly set. This design choice violates fundamental security principles by creating a predictable and writable entropy source that adversaries can compromise. The /tmp directory is typically world-writable and accessible to all local users, making it trivial for malicious actors to modify the entropy file contents. When the cryptographic system relies on this compromised entropy source, it significantly reduces the randomness and unpredictability of cryptographic operations, thereby weakening the overall security posture of SSL/TLS connections that depend on this library.
The operational impact of this vulnerability extends beyond simple cryptographic weakening to potentially enable more sophisticated attacks. By manipulating the entropy file, local users can effectively reduce the cryptographic strength of SSL/TLS operations, making it easier to predict random values used in cryptographic protocols. This weakness can be exploited to compromise the security of encrypted communications, potentially enabling man-in-the-middle attacks or other cryptographic attacks that rely on the predictability of random number generation. The vulnerability particularly affects systems where SSL/TLS connections are established through the libnet-ssleay-perl library, which is commonly used in Perl-based network applications and security tools.
This vulnerability aligns with CWE-310, which addresses cryptographic weaknesses related to entropy sources and random number generation, and represents a classic example of insecure default configuration. The flaw demonstrates how seemingly minor configuration issues can create significant security implications when they affect fundamental cryptographic operations. From an ATT&CK perspective, this vulnerability maps to techniques involving privilege escalation through configuration weaknesses and can be categorized under initial access and privilege escalation tactics. The attack surface is particularly concerning for systems where local users have access to the /tmp directory but should not be able to influence cryptographic operations.
Mitigation strategies for this vulnerability include updating to libnet-ssleay-perl version 1.25 or later, which addresses the insecure default behavior by requiring explicit entropy source configuration. Administrators should also ensure that the /tmp/entropy file is properly secured with restrictive permissions and ownership, preventing local users from modifying it. The recommended approach involves explicitly setting the egd_path variable to point to a secure entropy source such as /dev/urandom or a hardware random number generator. Additionally, system administrators should implement proper access controls and monitoring for the /tmp directory to detect unauthorized modifications to cryptographic entropy sources. Organizations should also conduct regular security assessments to identify other instances where insecure default configurations might be creating similar vulnerabilities in their cryptographic implementations.