Cybersecurity researchers have discovered a serious security issue that allows leaked Laravel APP_KEYs to be weaponized to gain remote code execution capabilities on hundreds of applications.
“Laravel’s APP_KEY, essential for encrypting sensitive data, is often leaked publicly (e.g., on GitHub),” GitGuardian said. “If attackers get access to this key, they can exploit a deserialization flaw to execute arbitrary code on the server – putting data and infrastructure at risk.”
The company, in collaboration with Synacktiv, said it was able to extract more than 260,000 APP_KEYs from GitHub from 2018 to May 30, 2025, identifying over 600 vulnerable Laravel applications in the process. GitGuardian said it observed over 10,000 unique APP_KEYs across GitHub, of which 400 APP_KEYs were validated as functional.
APP_KEY is a random 32-byte encryption key that’s generated during the installation of Laravel. Stored in the .env file of the application, it’s used to encrypt and decrypt data, generate secure, random strings, sign and verify data, and create unique authentication tokens, making a crucial security component.
GitGuardian noted that Laravel’s current implementation of decrypt() function introduces a security issue wherein it automatically deserializes decrypted data, thereby opening the door for possible remote code execution.
“Specifically in Laravel applications, if attackers obtain the APP_KEY and can invoke the decrypt() function with a maliciously crafted payload, they can achieve remote code execution on the Laravel web server,” security researcher Guillaume Valadon said.
“This vulnerability was first documented with CVE-2018-15133, which affected Laravel versions prior to 5.6.30. However, this attack vector persists in newer Laravel versions when developers explicitly configure session serialization in cookies using the SESSION_DRIVER=cookie setting, as demonstrated by CVE-2024-55556.”
It’s worth noting that CVE-2018-15133 has been exploited in the wild by threat actors associated with the AndroxGh0st malware, after scanning the internet for Laravel applications with misconfigured .env files.
Further analysis has found that 63% of APP_KEY exposures originate from .env files (or their variants) that typically contain other valuable secrets, such as cloud storage tokens, database credentials, and secrets associated with e-commerce platforms, customer support tools, and artificial intelligence (AI) services.
More importantly, approximately 28,000 APP_KEY and APP_URL pairs have been concurrently exposed on GitHub. Of these, approximately 10% have been found to be valid, rendering 120 applications vulnerable to trivial remote code execution attacks.
Given that the APP_URL configuration specifies the application’s base URL, exposing both APP_URL and APP_KEY creates a potent attack vector that threat actors can leverage to directly access the app, retrieve session cookies, and attempt to decrypt them using the exposed key.
Simply scrubbing secrets from repositories isn’t enough—especially when they’ve already been cloned or cached by third-party tools. What developers need is a clear rotation path, backed by monitoring that flags every future reappearance of sensitive strings across CI logs, image builds, and container layers.
“Developers should never simply delete exposed APP_KEYs from repositories without proper rotation,” GitGuardian said. “The proper response involves: immediately rotating the compromised APP_KEY, updating all production systems with the new key, and implementing continuous secret monitoring to prevent future exposures.”
These types of incidents also align with a broader class of PHP deserialization vulnerabilities, where tools like phpggc help attackers craft gadget chains that trigger unintended behaviors during object loading. When used in Laravel environments with leaked keys, such gadgets can achieve full RCE without needing to breach the app’s logic or routes.
The disclosure comes after GitGuardian revealed that it discovered a “staggering 100,000 valid secrets” in Docker images publicly accessible on the DockerHub registry. This includes secrets associated with Amazon Web Services (AWS), Google Cloud, and GitHub tokens.
A new Binarly analysis of over 80,000 unique Docker images spanning 54 organizations and 3,539 repositories has likewise uncovered 644 unique secrets that encompassed generic credentials, JSON Web Tokens, HTTP Basic Authorization header, Google Cloud API key, AWS access tokens, and CircleCI API tokens, among others.
“Secrets appear in a wide variety of file types, including source code, configuration files, and even large binary files, areas where many existing scanners fall short,” the company said. “Moreover, the presence of entire Git repositories inside container images represents a serious and often overlooked security risk.”
But that’s not all. The rapid adoption of Model Context Protocol (MCP) to enable agentic workflows in enterprise-driven AI applications has opened up brand new attack vectors – a concerning one being the leakage of secrets from MCP servers published to GitHub repositories.
Specifically, GitGuardian found that 202 of them leaked at least one secret, accounting for 5.2% of all the repositories – a number that the company said is “slightly higher than the 4.6% occurrence rate observed on all public repositories,” making MCP servers a “new source of secret leaks.”
While this research focuses on Laravel, the same root problem—unguarded secrets in public repositories—applies to other stacks. Organizations should explore centralized secret scanning, Laravel-specific hardening guides, and secure-by-design patterns for managing .env files and container secrets across frameworks.
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