CVE-2010-4237 in Mercurial
Summary
by MITRE
Mercurial before 1.6.4 fails to verify the Common Name field of SSL certificates which allows remote attackers who acquire a certificate signed by a Certificate Authority to perform a man-in-the-middle attack.
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Analysis
by VulDB Data Team • 10/30/2019
The vulnerability identified as CVE-2010-4237 represents a critical security flaw in the Mercurial distributed version control system that existed prior to version 1.6.4. This issue stems from the software's inadequate SSL certificate validation mechanism, specifically its failure to properly verify the Common Name field within SSL certificates. The Common Name field serves as a crucial component in SSL/TLS certificate validation, typically containing the domain name that the certificate is issued for, and its verification is fundamental to establishing trust between client and server. When this validation is bypassed, it creates a significant security gap that adversaries can exploit to compromise the integrity of communications.
The technical flaw manifests in Mercurial's SSL certificate handling routine where the software accepts certificates without properly validating that the certificate's Common Name matches the hostname being connected to. This omission allows attackers who have acquired a legitimate certificate from a Certificate Authority to perform man-in-the-middle attacks against Mercurial clients. The vulnerability operates under the principle that any certificate issued by a trusted CA is automatically trusted without additional validation of the certificate's intended use domain. This weakness aligns with CWE-295, which specifically addresses improper certificate validation in security protocols, and represents a classic example of insufficient certificate verification that undermines the entire SSL/TLS trust model.
The operational impact of this vulnerability is severe and far-reaching for organizations using Mercurial for version control operations. Attackers can intercept, modify, or redirect communications between Mercurial clients and servers, potentially compromising source code integrity, stealing sensitive data, or injecting malicious code into the development pipeline. This vulnerability particularly affects scenarios where Mercurial is used for secure repository access over HTTPS or SSH protocols, as it undermines the fundamental security assumptions that developers rely upon when performing operations such as pushing code changes, pulling updates, or accessing remote repositories. The vulnerability also impacts continuous integration systems and automated deployment processes that depend on secure Mercurial communications.
Organizations should immediately upgrade to Mercurial version 1.6.4 or later to remediate this vulnerability, as this update implements proper SSL certificate validation including Common Name field verification. Additionally, system administrators should conduct comprehensive security audits of their Mercurial installations to ensure no outdated versions remain in use. The mitigation strategy should include implementing certificate pinning where possible, establishing network monitoring to detect unusual SSL connection patterns, and ensuring that all Mercurial clients maintain updated certificate authorities to prevent acceptance of compromised certificates. From an ATT&CK framework perspective, this vulnerability maps to technique T1566 which covers credential harvesting through man-in-the-middle attacks, and T1046 which involves network service scanning that could be used to identify vulnerable Mercurial installations. Organizations should also consider implementing additional network security controls such as deep packet inspection and SSL/TLS protocol monitoring to detect and prevent exploitation attempts.