CVE-2026-44256 in Wazuh
Summary
by MITRE • 08/19/2026
Wazuh is a free and open source platform used for threat prevention, detection, and response. From 4.4.0 until 4.14.6 and 5.0.0-beta2, api/api/middlewares.py decodes the Basic authentication username before credential validation and passes it to the access logger without neutralizing control characters. api/api/alogging.py interpolates that value into the plain-text API log. An unauthenticated attacker can include carriage returns or line feeds in the username to forge entries, obscure activity, or poison systems that consume the plain-text audit log. The JSON log format is not affected because JSON serialization escapes these characters. This issue is fixed in versions 4.14.6 and 5.0.0-beta2.
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Analysis
by VulDB Data Team • 08/19/2026
Wazuh serves as a comprehensive open-source platform designed for threat prevention, detection, and response across distributed environments. Within the architecture of Wazuh, specifically between version 4.4.0 through 4.14.6 and up to 5.0.0-beta2, a critical security flaw exists in the application programming interface middleware layer. The vulnerability stems from improper handling of input data within the api/api/middlewares.py module during the authentication process. When an unauthenticated user attempts to access protected resources using Basic Authentication, the system decodes the username field before performing credential validation checks. This sequence of operations creates a window where maliciously crafted inputs can be processed by downstream logging components without adequate sanitization or neutralization of special control characters such as carriage returns and line feeds.
The core technical flaw lies in how the decoded username is passed to the access logger via api/api/alogging.py. The logging mechanism interpolates this unsanitized value directly into plain-text log files. Because standard text-based log formats do not inherently escape or handle non-printable control characters, an attacker can inject newline sequences into the username field of the HTTP Basic Authentication header. This injection allows the attacker to break out of the current log entry and append arbitrary content on new lines within the audit trail. While JSON-formatted logs are immune to this specific issue due their inherent serialization properties that escape special characters, the plain-text logging format remains vulnerable, exposing organizations relying on text-based log aggregation systems to significant risks.
The operational impact of this vulnerability is multifaceted and potentially severe for security operations centers. By injecting crafted entries into the audit log, an unauthenticated attacker can forge logs to obscure their actual malicious activities, making incident response and forensic analysis significantly more difficult. This technique effectively allows for log poisoning or manipulation, where false positive events are introduced to distract analysts or hide evidence of unauthorized access attempts. Furthermore, if these plain-text logs are consumed by downstream security information and event management systems or other automated processing tools that do not strictly validate input before parsing, the injected content could trigger unintended behaviors or even lead to remote code execution depending on how those consuming systems interpret the log data. This represents a classic case of injection via insufficient validation of user-supplied data in logging mechanisms.
From a classification perspective, this vulnerability aligns with CWE-117, which describes Improper Output Neutralization for Logs, as well as CWE-94, specifically the code injection variant where control characters are used to manipulate log structure. In terms of adversary tactics and techniques, this behavior maps directly to ATT&CK technique T1078.003, known as Valid Accounts: Local Accounts, although in this context it is exploited by unauthenticated actors through credential format manipulation rather than valid credentials. It also relates to T1562.001, Impair Defenses: Disable or Modify Tools, specifically the sub-technique of impairing log collection and analysis capabilities. The vulnerability highlights the critical importance of treating all input data as hostile until proven otherwise, even during preliminary stages like authentication header parsing before final credential verification.
To mitigate this risk, organizations must upgrade their Wazuh installations to version 4.14.6 or later, where the issue has been resolved by implementing proper neutralization and validation of control characters in the username field prior to logging. For environments that cannot immediately patch due to operational constraints, applying a web application firewall rule to block HTTP requests containing carriage return or line feed characters within authentication headers can provide temporary protection. Additionally, security teams should review their log ingestion pipelines to ensure they are resilient against malformed input and consider shifting critical audit logs from plain-text formats to structured JSON formats where possible, leveraging the inherent safety of JSON serialization for special characters. Regular auditing of log integrity and correlation with other telemetry sources remains essential to detect any successful exploitation attempts that may have occurred prior to remediation.