CVE-2026-54728 in BunkerWeb
Summary
by MITRE • 07/16/2026
bunkerweb is an Open-source and next-generation Web Application Firewall (WAF). Prior to BunkerWeb 1.6.12 and BunkerWeb PRO 0.57, authenticated Host header handling in the BunkerWeb UI and API improperly validated and neutralized user-controlled input in a configuration-dependent path, allowing a low-privileged authenticated user to escalate privileges and affect confidentiality, integrity, and availability of the BunkerWeb instance. This issue is fixed in BunkerWeb version 1.6.12 and BunkerWeb PRO version 0.57.
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Analysis
by VulDB Data Team • 07/16/2026
The BunkerWeb WAF vulnerability represents a critical privilege escalation flaw that emerged from inadequate input validation in the web application's host header handling mechanisms. This vulnerability affected versions prior to 1.6.12 for the open-source edition and 0.57 for the PRO edition, demonstrating how configuration-dependent paths can become attack vectors when proper sanitization controls are absent. The flaw specifically targeted authenticated users who could exploit the weak validation processes in the BunkerWeb user interface and API components.
The technical implementation of this vulnerability stems from improper neutralization of user-controlled input within host header processing logic. When authenticated users submitted malicious host headers through the UI or API endpoints, the system failed to adequately sanitize these inputs before processing them in configuration-dependent paths. This weakness allowed attackers to inject crafted host header values that could manipulate the application's behavior and potentially elevate their privileges beyond their intended access levels. The vulnerability aligns with CWE-20, which catalogs improper input validation issues, specifically focusing on scenarios where user-supplied data is not properly neutralized before being processed by the application.
The operational impact of this privilege escalation vulnerability extends across all three pillars of information security confidentiality, integrity, and availability. An attacker with low-privileged access could potentially gain administrative capabilities within the BunkerWeb instance, enabling them to modify firewall rules, access sensitive configuration data, or even disrupt service availability through malicious input injection. The configuration-dependent nature of the vulnerability means that the attack surface varied based on how the BunkerWeb instance was configured, but the fundamental flaw remained consistent across different deployment scenarios.
Mitigation strategies for this vulnerability require immediate deployment of patches to versions 1.6.12 and 0.57 respectively, which address the core input validation issues in host header processing. Organizations should implement comprehensive monitoring of authentication activities and host header usage patterns to detect potential exploitation attempts. The fix likely incorporates proper input sanitization techniques such as strict validation against whitelisted host patterns, encoding of special characters, and implementation of secure parsing mechanisms for HTTP headers. Additionally, security teams should conduct thorough assessments of the BunkerWeb configuration to ensure that no other similar validation gaps exist in related components.
From an ATT&CK framework perspective, this vulnerability maps to privilege escalation techniques within the credential access and defense evasion domains. The attack chain would typically involve initial access through legitimate authentication, followed by exploitation of the host header processing flaw to escalate privileges. This represents a sophisticated attack pattern that demonstrates how seemingly benign HTTP header processing can become a critical security weakness when proper input validation controls are absent, highlighting the importance of defense-in-depth approaches in web application security architectures.