CVE-2011-4078 in Roundcube
Summary
by MITRE
include/iniset.php in Roundcube Webmail 0.5.4 and earlier, when PHP 5.3.7 or 5.3.8 is used, allows remote attackers to trigger a GET request for an arbitrary URL, and cause a denial of service (resource consumption and inbox outage), via a Subject header containing only a URL, a related issue to CVE-2011-3379.
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Analysis
by VulDB Data Team • 11/25/2021
The vulnerability identified as CVE-2011-4078 represents a critical denial of service flaw in Roundcube Webmail versions 0.5.4 and earlier, specifically when deployed with PHP versions 5.3.7 or 5.3.8. This issue stems from improper handling of Subject headers containing only URL content, creating a scenario where remote attackers can manipulate the webmail application to initiate unintended GET requests to external resources. The vulnerability operates through a specific code path in the include/iniset.php file that fails to properly sanitize or validate incoming Subject header data before processing it within the application's parsing mechanisms. The flaw is particularly dangerous because it leverages the PHP version-specific behavior where certain URL parsing functions do not adequately validate input, allowing malicious actors to craft Subject headers that trigger resource-intensive operations.
The technical execution of this vulnerability involves attackers constructing Subject headers that contain only URL content, which then gets processed by Roundcube's internal parsing functions. When PHP encounters these malformed headers, it triggers a GET request to the specified URL without proper validation or rate limiting. This behavior creates a resource consumption issue where the webmail application continuously attempts to fetch resources from external servers, leading to excessive network bandwidth usage and potential server overload. The vulnerability is classified under CWE-400 as an Uncontrolled Resource Consumption vulnerability, specifically manifesting as a denial of service condition that affects both the application's performance and user accessibility. The operational impact extends beyond simple resource exhaustion to include complete inbox outages, making the webmail service unavailable to legitimate users while the malicious requests consume system resources.
The attack vector for CVE-2011-4078 is particularly insidious because it requires minimal privileges and can be executed through standard email submission processes. Attackers can send specially crafted emails with Subject headers containing malicious URLs, and the Roundcube application will attempt to process these requests without proper input validation. This vulnerability is related to CVE-2011-3379, indicating a broader class of issues affecting Roundcube's handling of URL content within email headers. The threat model aligns with ATT&CK technique T1499.004 for resource exhaustion attacks, where adversaries target application-level vulnerabilities to consume system resources and create denial of service conditions. The impact on organizations using vulnerable Roundcube installations includes service disruption, potential data loss, and increased operational costs due to system resource consumption and recovery efforts.
Mitigation strategies for CVE-2011-4078 focus on immediate patching of Roundcube installations to versions that properly validate Subject header content and implement input sanitization. Organizations should upgrade to Roundcube versions 0.6.0 or later, which contain fixes for this vulnerability and related issues. Additionally, implementing proper input validation at the application level, including sanitizing Subject headers and limiting URL processing capabilities, provides defense-in-depth measures. Network-level protections such as rate limiting on external resource requests and implementing proxy configurations that restrict outbound connections can help mitigate the impact of successful exploitation attempts. Security monitoring should include detection of unusual patterns in email processing and resource consumption that may indicate exploitation attempts. The vulnerability demonstrates the importance of proper input validation and the potential for PHP version-specific issues to create security weaknesses in web applications, reinforcing the need for comprehensive security testing across different runtime environments.