CVE-2026-29856 in aaPanel
Summary
by MITRE • 03/18/2026
An issue in the VirtualHost configuration handling/parser component of aaPanel v7.57.0 allows attackers to cause a Regular Expression Denial of Service (ReDoS) via a crafted input.
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Analysis
by VulDB Data Team • 03/24/2026
The vulnerability identified as CVE-2026-29856 resides within the VirtualHost configuration handling and parsing functionality of aaPanel version 7.57.0, representing a critical security flaw that exposes the system to Regular Expression Denial of Service attacks. This issue specifically affects how the application processes and validates VirtualHost configurations, creating an avenue for malicious actors to exploit the parsing component through carefully crafted input sequences that trigger excessive computational overhead.
The technical flaw manifests in the improper handling of regular expressions used during VirtualHost configuration parsing operations. When an attacker submits malicious input containing specially constructed patterns, the regular expression engine becomes vulnerable to catastrophic backtracking behavior, where the parsing process consumes exponentially increasing amounts of CPU time and memory resources. This vulnerability falls under the CWE-400 category of Uncontrolled Resource Consumption, specifically targeting the Regular Expression Denial of Service pattern. The attack vector leverages the application's failure to implement proper input validation and sanitization mechanisms for configuration parameters that are subsequently processed through regular expression matching operations.
The operational impact of this vulnerability extends beyond simple service disruption, potentially allowing attackers to exhaust system resources and render the aaPanel management interface unavailable to legitimate users. The ReDoS attack can be executed with minimal privileges and requires only the ability to submit configuration data to the vulnerable system, making it particularly dangerous in multi-tenant hosting environments where individual users might exploit this weakness to affect the entire hosting platform. This vulnerability directly maps to ATT&CK technique T1499.004, which involves resource exhaustion attacks through manipulation of input validation logic, and represents a significant threat to system availability and operational continuity.
Mitigation strategies should focus on implementing proper input validation and sanitization measures that prevent malicious regular expression patterns from reaching the parsing engine. The recommended approach includes upgrading to aaPanel version 7.57.1 or later, which contains patched regular expression handling logic, implementing rate limiting on configuration submission endpoints, and employing input whitelisting techniques that restrict VirtualHost configuration parameters to predefined safe patterns. Additionally, organizations should consider implementing automated monitoring for unusual CPU consumption patterns and establish proper security testing procedures that include regular vulnerability assessments of parsing components to prevent similar issues from emerging in future releases.