CVE-2026-54543 in Froxlor
Summary
by MITRE • 08/19/2026
Froxlor is open source server administration software. Prior to 2.3.8, the DomainZones.add API command in lib/Froxlor/Api/Commands/DomainZones.php accepts user-controlled record and type values without rejecting line delimiters, tab characters, semicolons, or unsupported DNS record types before lib/Froxlor/Dns/DnsEntry.php serializes the values into a BIND zone file. An authenticated customer with DNS-zone permissions can place a crafted value in the record field, or use the related type-field variant, to create additional resource-record lines that bypass Froxlor's field-level validation. BIND accepts the injected records, allowing modification of DNS data and possible DNS availability impact within a zone the caller is authorized to manage. This issue is fixed in version 2.3.8.
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Analysis
by VulDB Data Team • 08/19/2026
The vulnerability identified in Froxlor prior to version 2.3.8 represents a critical input validation failure within its DomainZones.add API command, specifically located in lib/Froxlor/Api/Commands/DomainZones.php. As an open-source server administration tool, Froxlor manages various hosting configurations, including DNS zone files which are typically serialized into BIND format for use by authoritative name servers. The core technical flaw arises from the application's failure to sanitize user-controlled inputs before they are processed by the serialization logic in lib/Froxlor/Dns/DnsEntry.php. Specifically, the record and type fields accept arbitrary strings without rejecting dangerous characters such as line delimiters, tab characters, or semicolons, nor does it strictly enforce a whitelist of supported DNS record types during the initial input phase. This lack of rigorous validation allows an attacker to inject additional resource-record lines directly into the zone file structure by embedding newline characters within the value fields intended for single-line entries.
From an operational perspective, this flaw enables authenticated customers who possess DNS-zone permissions to perform a form of server-side request forgery or data injection that bypasses Froxlor's field-level validation mechanisms. By crafting specific values containing line breaks or other control characters, an attacker can effectively append unauthorized DNS records to the zone file managed by their account. When BIND processes this modified zone file, it accepts these injected records as legitimate configuration directives. This capability allows for significant manipulation of DNS data within a zone that the caller is authorized to manage. The immediate impact includes the potential for DNS cache poisoning if an attacker can inject records pointing to malicious infrastructure, or more broadly, a denial of service by corrupting the zone file structure such that BIND fails to load it correctly. Furthermore, this vulnerability could facilitate phishing campaigns by allowing attackers to add subdomains that resolve to fraudulent websites while maintaining the appearance of legitimacy under their managed domain.
This issue aligns with Common Weakness Enumeration (CWE) categories related to improper input validation and injection flaws. Specifically, it reflects CWE-20 Improper Input Validation, as the application fails to verify that user-supplied data conforms to expected formats before processing. Additionally, because the vulnerability allows for the modification of system configuration files through injected commands or structures, it relates closely to CWE-94 Code Injection principles, albeit in a configuration file context rather than executable code execution. In terms of tactical mapping within the MITRE ATT&CK framework, this behavior is consistent with techniques involving Data Manipulation and potentially Command and Control if used to establish persistent DNS-based communication channels or redirect traffic for interception purposes. The attack vector requires authentication, classifying it as an authenticated insider threat scenario rather than a remote unauthenticated exploit, which limits its scope but increases the severity of compromise within trusted environments.
Mitigation strategies focus primarily on upgrading the Froxlor installation to version 2.3.8 or later, where this validation logic has been corrected to properly reject line delimiters and enforce strict type checking before serialization. For organizations unable to immediately patch, implementing a Web Application Firewall (WAF) rule set that detects and blocks HTTP requests containing newline characters in parameters associated with DNS record creation can provide temporary protection. Additionally, administrators should review access controls for the DomainZones API endpoint, ensuring that only necessary users have write permissions to DNS zone configurations. Regular auditing of BIND zone files generated by Froxlor can also help detect any unauthorized modifications resulting from exploitation attempts prior to patching. It is crucial to treat all user inputs destined for configuration file generation with extreme skepticism and enforce strict allow-listing of acceptable characters and formats at the application layer rather than relying solely on downstream parsers like BIND to reject malformed data.