CVE-2011-3634 in apt
Summary
by MITRE
methods/https.cc in apt before 0.8.11 accepts connections when the certificate host name fails validation and Verify-Host is enabled, which allows man-in-the-middle attackers to obtain repository credentials via unspecified vectors.
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Analysis
by VulDB Data Team • 04/12/2025
The vulnerability described in CVE-2011-3634 resides within the Advanced Package Tool implementation specifically in the methods/https.cc component of apt versions prior to 0.8.11. This flaw represents a critical security weakness in the package management system's handling of secure communications, particularly when dealing with repository connections that employ HTTPS encryption. The issue manifests when the system encounters certificate hostname validation failures while the Verify-Host configuration parameter remains enabled, creating a dangerous operational scenario where security controls are effectively bypassed.
The technical flaw stems from improper certificate validation logic within the apt package manager's HTTPS handling mechanism. When a repository certificate fails hostname validation checks, the system should reject the connection to prevent potential man-in-the-middle attacks. However, due to this vulnerability, apt continues to accept connections despite certificate validation failures, effectively rendering the hostname verification mechanism useless. This behavior creates a scenario where attackers can intercept communications between the package manager and repository servers, potentially capturing sensitive information including repository credentials that are transmitted during package installation processes. The vulnerability operates at the transport layer security level, specifically targeting the certificate validation routines that are fundamental to establishing trust in secure communications.
The operational impact of this vulnerability is significant and multifaceted. Attackers exploiting this weakness can perform man-in-the-middle attacks against package repository communications, potentially gaining access to repository credentials and other sensitive data. This compromise extends beyond simple credential theft to potentially enable more sophisticated attacks such as package injection, where malicious actors could replace legitimate packages with compromised versions. The vulnerability affects systems using apt package management on Linux distributions, particularly those that rely on HTTPS repositories for package distribution. Organizations using affected versions of apt face the risk of supply chain attacks where compromised repositories could distribute malicious software to multiple systems simultaneously, making the impact potentially widespread across networked environments.
Mitigation strategies for CVE-2011-3634 involve immediate upgrades to apt versions 0.8.11 or later where the certificate validation logic has been corrected. System administrators should also implement additional security controls such as verifying repository GPG signatures, monitoring network traffic for suspicious activities, and considering alternative package sources when available. The vulnerability aligns with CWE-295, which specifically addresses improper certificate validation, and represents a clear violation of the principle of least privilege in secure communications. From an ATT&CK framework perspective, this vulnerability maps to techniques involving credential access and supply chain compromise, as it enables attackers to obtain repository credentials and potentially manipulate package distribution channels. Organizations should also consider implementing network segmentation and monitoring solutions to detect anomalous package management activities that might indicate exploitation attempts. The remediation process requires careful testing of updated apt versions to ensure compatibility with existing package management workflows while maintaining security posture.