CVE-2026-86522 in ash_authentication
Summary
by MITRE • 09/17/2026
Improper Output Neutralization for Logs vulnerability in team-alembic AshAuthentication allows an unauthenticated attacker to forge application log entries by submitting a password reset identity containing newlines or control characters.
AshAuthentication.Strategy.Password.RequestPasswordReset.run/3 interpolates the identity argument, the email or username taken straight from the reset request, into its Logger.warning/1 heredocs without escaping, truncating or type-restricting it. The resource logged beside it is passed through inspect/1, which would have neutralized the value. A newline in the identity therefore ends the log record, and everything after it is written as a line of its own, so an attacker chooses the severity tag and the content of entries that appear to have come from the application.
This issue affects ash_authentication: from 4.2.0 before 4.15.0 and from 5.0.0-rc.0 before 5.0.0-rc.14.
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Analysis
by VulDB Data Team • 09/17/2026
The vulnerability identified as Improper Output Neutralization for Logs in the AshAuthentication library represents a significant security risk within applications utilizing this authentication framework, specifically affecting versions ranging from 4.2.0 up to but not including 4.15.0 and from 5.0.0-rc.0 up to but not including 5.0.0-rc.14. This flaw stems directly from the implementation of the password reset functionality, where user-supplied input is inadequately sanitized before being written to application logs. The core technical issue resides in the AshAuthentication.Strategy.Password.RequestPasswordReset.run/3 function, which handles the initiation of a password reset request by accepting an identity argument that typically contains either an email address or a username provided directly by the end-user during the submission process.
When this untrusted input is processed for logging purposes, it is interpolated into Logger.warning heredocs without any form of escaping, truncation, or type restriction designed to neutralize special characters. While other parts of the codebase may employ functions like inspect/1 which would effectively sanitize such values by converting them into a safe string representation that prevents injection, this specific logging path fails to apply similar protections. Consequently, if an attacker submits a password reset identity containing newline characters or control codes, these characters are interpreted literally by the log system rather than being treated as part of the data payload. This lack of neutralization allows the input to break out of its intended line context within the log file structure.
The operational impact of this vulnerability is severe because it enables an unauthenticated attacker to forge application log entries with arbitrary content and severity levels. By injecting newlines, the attacker can terminate the current log record and append subsequent text that appears as a separate entry in the logs. This capability allows the adversary to manipulate the perceived state or events recorded by the system, potentially masking malicious activities such as brute-force attacks or unauthorized access attempts while simultaneously creating false alerts that could mislead security monitoring teams. The ability to control both the severity tag and the content of these entries undermines the integrity of audit trails, which are critical for forensic analysis and compliance with regulatory standards requiring accurate logging of authentication events.
From a classification perspective, this vulnerability aligns closely with CWE-117, Improper Output Neutralization for Logs, as it involves the injection of log data through insufficient sanitization of user input. Furthermore, in terms of tactical behavior within an attack lifecycle, this technique relates to ATT&CK T1078, Valid Accounts, or more specifically aspects of Log Injection which can be used to evade detection mechanisms by altering logs to remove evidence of intrusion or create confusion among analysts. The exploitation does not require prior authentication, making it accessible to any external actor who can interact with the password reset endpoint, thereby expanding the attack surface significantly compared to vulnerabilities that require privileged access.
Mitigation strategies must focus on ensuring that all user-supplied data intended for logging is strictly sanitized before being passed to loggers. Developers should implement robust input validation and output encoding practices specifically tailored for log contexts, such as replacing newline characters with safe alternatives or using structured logging formats like JSON which inherently separate metadata from message content, thereby preventing line-based injection attacks. Upgrading the AshAuthentication library to version 4.15.0 or later, or versions 5.0.0-rc.14 and beyond for the five series, is the primary remediation step as these releases address this specific interpolation flaw. Additionally, implementing centralized log management solutions with built-in sanitization capabilities can provide an additional layer of defense against such injection attempts, ensuring that even if application-level controls fail, the integrity of the logging infrastructure remains intact.