CVE-2025-58759 is a medium severity vulnerability affecting versions 1.0.9 and 1.0.10 of TinyEnv, a PHP environment variable loader developed by datahihi1. The core issue stems from improper input validation (CWE-20) where TinyEnv fails to correctly strip inline comments within .env file values. Specifically, when environment variables contain inline comments (denoted by characters like '#'), TinyEnv does not remove these comment portions, causing the loaded environment variables to include unintended characters or comment text. This behavior can lead to unexpected application logic errors, misconfigurations, or insecure default settings. For example, an environment variable intended to hold a secret key or configuration flag might be corrupted by appended comment text, potentially causing authentication failures or enabling insecure fallback behaviors. The vulnerability does not require user interaction or privileges to exploit but does require local access to the environment files or the ability to influence their contents. The CVSS 3.1 base score is 5.1 (medium), reflecting low attack vector (local), low complexity, no privileges required, no user interaction, and limited confidentiality and integrity impacts without availability impact. The issue is resolved in TinyEnv version 1.0.11. Until upgrading, users are advised to avoid inline comments in .env files or manually sanitize environment variable values after loading. No known exploits are currently reported in the wild.

For European organizations using PHP applications that rely on TinyEnv versions 1.0.9 or 1.0.10, this vulnerability can cause subtle but critical misconfigurations. Since environment variables often control authentication credentials, API keys, or feature toggles, corrupted values due to inline comments can lead to authentication bypasses, exposure of insecure defaults, or application logic errors. This can degrade the confidentiality and integrity of sensitive data and potentially allow unauthorized access or privilege escalation within the application context. Although the vulnerability requires local or deployment-level access to exploit, compromised development or deployment pipelines, or insider threats, could leverage this flaw to weaken security postures. The impact is particularly significant for organizations with strict compliance requirements (e.g., GDPR) where misconfiguration-induced data leaks or unauthorized access could lead to regulatory penalties. Additionally, the lack of availability impact means service disruption is unlikely, but silent security failures may go unnoticed, increasing risk exposure.

European organizations should immediately upgrade TinyEnv to version 1.0.11 or later to fully remediate this vulnerability. Until the upgrade is feasible, developers and DevOps teams must avoid using inline comments within .env files to prevent corrupted environment variable values. Implementing manual sanitization routines post environment loading can help strip unintended characters or comment text from variables. Additionally, organizations should audit existing .env files for inline comments and validate environment variable values during deployment and runtime. Incorporating automated static analysis or configuration scanning tools that detect improper environment variable formats can further reduce risk. Secure development lifecycle practices should enforce strict environment file formatting guidelines and restrict write access to .env files to trusted personnel only. Monitoring application logs for authentication anomalies or configuration errors can help detect exploitation attempts early.