CVE-2014-1959 in GnuTLS
Summary
by MITRE
lib/x509/verify.c in GnuTLS before 3.1.21 and 3.2.x before 3.2.11 treats version 1 X.509 certificates as intermediate CAs, which allows remote attackers to bypass intended restrictions by leveraging a X.509 V1 certificate from a trusted CA to issue new certificates.
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Analysis
by VulDB Data Team • 05/07/2026
The vulnerability described in CVE-2014-1959 represents a critical flaw in the GnuTLS cryptographic library that affects versions prior to 3.1.21 and 3.2.11. This issue stems from the improper handling of X.509 version 1 certificates during the certificate verification process, creating a significant security bypass opportunity for remote attackers. The flaw specifically impacts how the library treats version 1 certificates, which should normally be restricted in their capabilities compared to version 2 and 3 certificates that contain more comprehensive extension fields and validation requirements.
The technical root cause of this vulnerability lies in the certificate verification logic implemented in lib/x509/verify.c within the GnuTLS codebase. When processing X.509 version 1 certificates, the library incorrectly classifies these certificates as intermediate certificate authorities rather than recognizing them as the limited capabilities they actually possess. This misclassification occurs because version 1 certificates lack the basic constraints extension that would normally indicate their restricted status as end-entity certificates. The improper handling allows an attacker to exploit this logic flaw to effectively elevate the privileges of a version 1 certificate, enabling it to act as if it were an intermediate CA capable of issuing new certificates.
The operational impact of this vulnerability is substantial as it fundamentally undermines the certificate chain validation process that security protocols rely upon. Remote attackers can leverage this weakness to bypass intended certificate restrictions by presenting a trusted version 1 certificate from a legitimate CA and using it to issue new certificates that would otherwise be prohibited. This creates a scenario where attackers can potentially forge certificates that appear legitimate to systems using vulnerable GnuTLS versions, effectively breaking the trust model that certificate authorities establish. The attack vector is particularly concerning because it operates at the cryptographic library level, meaning that any application using vulnerable GnuTLS versions could be compromised without the application developer's knowledge or control.
This vulnerability aligns with CWE-295 which addresses improper certificate validation and relates to the broader category of trust management flaws in cryptographic systems. The issue also maps to ATT&CK technique T1552.001 which covers "Unsecured Credentials" and T1552.006 which covers "Credentials in Files" as the flaw enables attackers to manipulate certificate validation processes that are critical for maintaining secure communications. The flaw essentially allows for credential manipulation through certificate forgery, where the compromised certificate can be used to establish secure connections that appear legitimate to clients and servers.
Organizations and developers using GnuTLS should immediately upgrade to versions 3.1.21 or 3.2.11 and later to remediate this vulnerability. System administrators should conduct comprehensive audits of all systems using vulnerable GnuTLS versions to identify potential attack surfaces and implement additional monitoring for suspicious certificate issuance patterns. The mitigation strategy should include not only the software upgrade but also the implementation of certificate monitoring systems that can detect anomalous certificate issuance patterns that might indicate exploitation attempts. Additionally, organizations should review their certificate trust stores to ensure that only properly configured and validated certificates are trusted by their systems, as this vulnerability specifically targets the trust validation process itself rather than the certificate content or the cryptographic algorithms used.