CVE-2026-16648 in Mailer Plus Log Plugin
Summary
by MITRE • 10/22/2026
Insertion of Sensitive Information into Log File vulnerability in Drupal Mailer Plus Log allows Remote Services with Stolen Credentials. This issue affects Mailer Plus Log versions: from 0.0.0 to 1.2.7.
If you want to get best quality of vulnerability data, you may have to visit VulDB.
Analysis
by VulDB Data Team • 10/22/2026
The vulnerability identified as an insertion of sensitive information into a log file within the Drupal module Mailer Plus Log represents a significant data exposure risk for organizations utilizing this extension. This flaw specifically impacts version ranges from 0.0.0 up through and including version 1.2.7, indicating that any deployment operating on these older iterations is susceptible to unauthorized access of confidential operational data. The core technical deficiency lies in the module's logging mechanism, which fails to sanitize or mask sensitive authentication credentials before writing them to persistent storage logs. When a remote service attempts to authenticate using stolen or compromised credentials against an affected Drupal instance, the Mailer Plus Log component records these details directly into log files without applying necessary obfuscation techniques such as hashing, masking with asterisks, or excluding specific fields entirely from the output stream.
From a technical perspective, this behavior constitutes a classic case of improper input validation and sanitization within logging subsystems. The application logic treats all incoming data destined for logs as safe to record, ignoring the classification of certain parameters like usernames, passwords, API keys, or session tokens as sensitive material. This oversight allows an attacker who has obtained valid credentials through phishing, credential stuffing, or other initial access vectors to leverage this vulnerability further by accessing server-side log files where these secrets are stored in plaintext. The presence of such data in logs creates a secondary attack vector that extends beyond the immediate authentication failure, potentially leading to full account compromise if the logging directory is accessible via web traversal, local file inclusion vulnerabilities elsewhere in the application stack, or through insufficient filesystem permissions on the hosting environment.
The operational impact of this vulnerability is severe due to its potential for lateral movement and privilege escalation within a compromised infrastructure. Once an attacker gains access to these log files, they can extract valid credentials that may be reused across other services if users practice password reuse, which remains prevalent in many enterprise environments. Furthermore, the exposure of internal service accounts or API keys found in logs can allow attackers to interact with backend systems, databases, or third-party integrations without triggering standard intrusion detection alerts associated with brute force attempts. This aligns directly with Common Weakness Enumeration identifier CWE-532, which defines information leakage through log files as a distinct security weakness. The attack pattern also correlates with MITRE ATT&CK technique T1078, Valid Accounts, where adversaries use legitimate credentials to maintain persistence and expand their foothold within the network perimeter.
Mitigation strategies must address both immediate remediation and long-term logging hygiene practices. The primary and most effective solution is to upgrade the Mailer Plus Log module to a version later than 1.2.7, assuming the vendor has implemented proper sanitization in subsequent releases. If upgrading is not immediately feasible due to compatibility constraints or testing requirements, administrators should implement compensating controls at the infrastructure level. This includes restricting file system permissions on log directories so that only privileged service accounts can read them, thereby preventing web-based attackers from accessing logs via HTTP requests. Additionally, organizations should review their logging configurations across all Drupal modules to ensure no other components are inadvertently exposing sensitive data such as passwords or tokens in plaintext format. Implementing centralized log management solutions with built-in redaction capabilities and regular audits of log content can further reduce the risk profile associated with this class of vulnerability.