CVE-2010-2074 in w3m
Summary
by MITRE
istream.c in w3m 0.5.2 and possibly other versions, when ssl_verify_server is enabled, does not properly handle a \0 character in a domain name in the (1) subject s Common Name or (2) Subject Alternative Name 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 • 07/30/2024
The vulnerability identified as CVE-2010-2074 resides within the w3m web browser version 0.5.2 and potentially other versions, specifically affecting the SSL certificate validation mechanism when ssl_verify_server is enabled. This flaw represents a critical security weakness in the handling of X.509 certificate subject fields, particularly concerning the Common Name and Subject Alternative Name components. The vulnerability stems from the improper processing of null characters within domain names during SSL certificate verification, creating a pathway for malicious actors to bypass security checks.
The technical flaw manifests when the w3m browser encounters an X.509 certificate containing a null character within the subject's Common Name or Subject Alternative Name fields. This null character handling issue allows attackers to craft certificates that appear valid to the browser while actually pointing to malicious servers. The vulnerability operates through a buffer handling or string parsing mechanism that fails to properly sanitize or validate the presence of null characters in certificate subject fields. This weakness directly relates to the broader class of issues involving improper input validation and string manipulation in cryptographic libraries, as classified under CWE-170.
From an operational perspective, this vulnerability enables sophisticated man-in-the-middle attacks where attackers can impersonate legitimate SSL servers by creating certificates with null characters in their domain names. The impact extends beyond simple certificate validation failures, as it undermines the fundamental trust model of SSL/TLS communications. Attackers can exploit this weakness to intercept sensitive data, perform session hijacking, or redirect users to malicious websites while maintaining the appearance of legitimate secure connections. The vulnerability is particularly dangerous because it operates silently, allowing attackers to establish fraudulent connections without alerting users to the security compromise.
The security implications of CVE-2010-2074 align with several ATT&CK framework techniques including T1573.002 (SSL/TLS Spoofing) and T1071.004 (Application Layer Protocol: DNS). This vulnerability represents a classic case of insufficient input validation that can be exploited to bypass security controls, making it particularly concerning for systems relying on w3m for secure web browsing. Organizations using affected versions of w3m should immediately implement mitigations including updating to patched versions, disabling SSL verification where possible, and monitoring for suspicious certificate activity. The vulnerability also highlights the importance of proper string handling in cryptographic implementations and serves as a reminder of the critical need for comprehensive input validation in security-sensitive code paths. This issue demonstrates how seemingly minor parsing flaws can create significant security risks in SSL/TLS implementations, emphasizing the need for rigorous testing of certificate validation logic against various edge cases and malformed inputs.