CVE-2009-2474 in neon
Summary
by MITRE
neon before 0.28.6, when OpenSSL or GnuTLS is used, does not properly handle a \0 character in a domain name in the subject s Common Name (CN) field of an X.509 certificate, which allows man-in-the-middle attackers to spoof arbitrary SSL servers via a crafted certificate issued by a legitimate Certification Authority, a related issue to CVE-2009-2408.
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Analysis
by VulDB Data Team • 08/20/2021
The vulnerability identified as CVE-2009-2474 affects the neon library version 0.28.6 and earlier, specifically when utilizing OpenSSL or GnuTLS cryptographic libraries. This flaw resides in the X.509 certificate validation process where the library fails to properly handle null character sequences within the Common Name field of SSL certificates. The issue represents a critical security weakness that undermines the fundamental trust model of SSL/TLS communications by allowing attackers to craft malicious certificates that appear legitimate to vulnerable systems.
The technical flaw manifests when a certificate contains a null character within the Common Name field of its subject section. During SSL/TLS handshake operations, the neon library processes this malformed certificate without proper validation, leading to a failure in certificate chain validation. This vulnerability operates under the broader category of certificate validation weaknesses, specifically related to the handling of special characters in certificate subject fields. The null character injection creates a parsing inconsistency that bypasses normal certificate verification procedures, effectively allowing attackers to establish fraudulent SSL connections that appear to be from legitimate servers.
The operational impact of this vulnerability is severe and directly enables man-in-the-middle attacks against systems using vulnerable versions of neon. Attackers can generate certificates with null characters in the Common Name field that will be accepted by vulnerable applications, allowing them to impersonate legitimate SSL servers without detection. This creates a significant risk for any system that relies on SSL/TLS certificate validation for secure communications, including web servers, email servers, and other network services that use the neon library for HTTP and WebDAV operations. The vulnerability essentially undermines the cryptographic security guarantees that SSL/TLS is designed to provide.
The security implications extend beyond simple certificate validation failures and represent a direct threat to the integrity of secure communications. This vulnerability aligns with CWE-295, which addresses improper certificate validation, and relates to the broader category of certificate manipulation attacks. From an ATT&CK framework perspective, this vulnerability enables T1573.002 (Encrypted Channel) and T1071.004 (Application Layer Protocol: DNS) techniques, as attackers can establish fraudulent secure channels. Organizations using vulnerable versions of neon should immediately implement mitigations including upgrading to version 0.28.6 or later, implementing additional certificate validation checks, and monitoring for suspicious certificate usage patterns. The vulnerability also highlights the importance of proper input sanitization in cryptographic libraries and demonstrates how seemingly minor parsing issues can create significant security weaknesses in critical infrastructure components.