Summary
HashBrown CMS contains an OS command injection vulnerability in its Git deployer because the configured branch value is inserted directly into a shell command without adequate escaping. A user who can modify a project's Git deployer settings may cause commands to execute when deployment-related operations trigger repository synchronization.
Affected context
The vulnerability occurs in HashBrown CMS deployments using the Git deployer component through version 1.4.6. It becomes risky when an attacker can configure or modify a project's Git deployer settings and the application subsequently performs an operation that invokes repository synchronization, such as media uploads or content saves.
Exploit preconditions
- Attack surface: Git deployer configuration and subsequent deployment-related operations
- Required access: Permission to create or modify a project's Git deployer settings
- Trigger point: Repository synchronization performed at the start of deployer operations
- Why exploitation is possible: The configured branch value is interpolated into a shell command without robust argument separation or shell metacharacter handling
Why this happens
The underlying bug is command construction from attacker-influenced configuration data. GitDeployer builds a shell command by concatenating the branch value into a command string, while validation does not comprehensively prevent shell control characters or command substitutions. This behavior maps to CWE-78: Improper Neutralization of Special Elements used in an OS Command, because input is interpreted by a shell as command syntax rather than treated solely as a data argument.
Potential impact
- An attacker may execute arbitrary operating-system commands with the application's privileges
- The application host or deployment worker could be compromised
- Repository contents, credentials, or deployment artifacts could be exposed or altered
- Malicious changes could be introduced into published content or downstream systems
- The compromised process could be used for further lateral movement, depending on available permissions
General mitigation guidance
Mitigation generally focuses on preventing configuration values from becoming shell syntax.
Common defensive patterns include:
- Invoke Git through an argument-based process API rather than a shell command string
- Treat branch names as data and enforce a strict allowlist or repository-specific branch-name policy
- Apply validation before any command construction or process execution
- Reduce the privileges of the application and deployment process
- Keep deployer credentials and repository access scoped to the minimum required operations
- Restrict which users or roles can modify Git deployer settings
- Avoid relying on single-character filtering as a substitute for safe process invocation
How teams detect issues like this
Organizations can look for:
- Static analysis findings where configuration fields are concatenated into shell commands
- Code review signals involving command execution APIs, shell-enabled process spawning, and string interpolation
- Tests using shell metacharacters and command-substitution syntax as validation cases, without executing them in production
- Audit events showing unexpected changes to Git deployer settings or branch configuration
- Runtime monitoring for unusual child processes, command interpreters, or outbound connections from the CMS process
- Policy enforcement requiring argument-vector process APIs and restricting shell execution in application code
Automated security scanning and code review tools may help identify these patterns when configured for command-injection rules.
