CVE-2011-4761 in Plesk Small Business Panel
Summary
by MITRE
Parallels Plesk Small Business Panel 10.2.0 omits the Content-Type header s charset parameter for certain resources, which might allow remote attackers to have an unspecified impact by leveraging an interpretation conflict involving domains/sitebuilder_edit.php and certain other files. NOTE: it is possible that only clients, not the SmarterStats product, could be affected by this issue.
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Analysis
by VulDB Data Team • 01/10/2018
The vulnerability identified as CVE-2011-4761 affects Parallels Plesk Small Business Panel version 10.2.0 and represents a significant security flaw related to HTTP header handling within the web application. This issue specifically concerns the omission of the charset parameter in Content-Type headers for certain resources, creating potential for interpretation conflicts that could be exploited by remote attackers. The vulnerability manifests in the context of domain management and site builder functionality, particularly involving the domains/sitebuilder_edit.php file and related components within the Plesk control panel interface. The affected system's failure to properly specify character encoding in HTTP responses creates ambiguity in how browsers and other HTTP clients interpret the received content, potentially leading to unexpected behavior or security implications.
The technical flaw stems from improper HTTP header construction where the Content-Type header lacks the charset parameter specification, particularly for dynamic content served by the Plesk panel. This omission creates an interpretation conflict scenario where different systems may default to different character encodings when processing the same content, potentially leading to cross-site scripting vulnerabilities or other injection-based attacks. The vulnerability is classified under CWE-1004 which deals with Security Weaknesses in HTTP Headers, specifically addressing the absence of proper character encoding specifications. When browsers encounter content without explicit charset information, they may fall back to default encodings or attempt to detect encoding through heuristics, creating opportunities for attackers to manipulate how content is interpreted and processed.
The operational impact of this vulnerability extends beyond simple content rendering issues and could potentially allow remote attackers to exploit the interpretation conflict for more serious security breaches. The unspecified impact mentioned in the CVE description suggests that depending on the specific implementation details and client configurations, attackers might be able to manipulate how content is processed, potentially leading to XSS attacks, data injection, or other malicious activities. The attack surface includes not only the primary affected file domains/sitebuilder_edit.php but also other related files within the Plesk panel that may exhibit similar behavior. This vulnerability is particularly concerning in environments where Plesk is used for managing multiple domains and sites, as it could provide attackers with opportunities to compromise the entire hosting environment through manipulation of character encoding interpretations.
The security implications of this vulnerability align with ATT&CK technique T1059.007 which covers "Command and Scripting Interpreter: JavaScript" and related techniques involving content injection and interpretation manipulation. While the vulnerability itself is not directly classified as a command injection or code execution flaw, the character encoding ambiguity creates conditions where attackers could potentially exploit the interpretation conflict to inject malicious content that would be processed differently than intended. The potential for impact varies significantly based on the specific environment and client configurations, with some scenarios potentially affecting only client-side applications while others might allow more serious server-side exploitation. Organizations using Plesk 10.2.0 should consider this vulnerability as part of a broader security assessment, particularly in environments where multiple domains are managed through the same control panel instance.
Mitigation strategies for CVE-2011-4761 should focus on implementing proper Content-Type header construction across all web resources served by the Plesk panel. System administrators should ensure that all HTTP responses include explicit charset parameters in their Content-Type headers, typically following the format "Content-Type: text/html; charset=utf-8" for HTML content. The most effective immediate fix involves upgrading to a patched version of Parallels Plesk Small Business Panel, as version 10.2.0 is known to contain this vulnerability. Organizations should also implement monitoring for HTTP headers to detect similar issues in other applications within their infrastructure. Additionally, implementing proper input validation and output encoding practices can help reduce the potential impact of any exploitation attempts, though the primary fix requires addressing the root cause in the Plesk panel's header generation logic. Network-level protections such as web application firewalls may provide additional defense-in-depth but should not be considered a substitute for proper header implementation.