CVE-2026-27626: OliveTin Shell Command RCE Vulnerability

CVE-2026-27626 Overview

OliveTin is an application that provides access to predefined shell commands through a web interface. A critical command injection vulnerability has been identified in OliveTin versions up to and including 3000.10.0 that allows attackers to execute arbitrary operating system commands through two independent attack vectors.

The first vector exploits a flaw in OliveTin's shell mode safety check function (checkShellArgumentSafety), which blocks several dangerous argument types but fails to sanitize password-typed arguments. An attacker can supply a password-typed argument containing shell metacharacters that execute arbitrary OS commands on the underlying system.

The second, more severe vector enables unauthenticated remote code execution through webhook-extracted JSON values that completely bypass type safety checks before being passed to sh -c for execution.

Critical Impact

Unauthenticated remote code execution on any OliveTin instance using Shell mode with webhook-triggered actions, potentially compromising the entire host system with the permissions of the OliveTin process.

Affected Products

• OliveTin versions up to and including 3000.10.0

Discovery Timeline

• 2026-02-25 - CVE CVE-2026-27626 published to NVD
• 2026-02-25 - Last updated in NVD database

Technical Details for CVE-2026-27626

Vulnerability Analysis

This vulnerability is classified as CWE-78 (Improper Neutralization of Special Elements used in an OS Command), commonly known as OS Command Injection. The vulnerability presents two distinct exploitation paths that can lead to full system compromise.

The first attack vector targets authenticated users and exploits insufficient input validation in the checkShellArgumentSafety function. While this function implements safety checks for various dangerous argument types, it explicitly omits validation for password-typed arguments. Since registration is enabled by default and authType: none is the default authentication configuration, the barrier to authenticated exploitation is minimal.

The second attack vector is significantly more dangerous as it requires no authentication whatsoever. When OliveTin processes webhooks from external sources—a primary use case for the application—JSON values extracted from webhook payloads are passed directly to sh -c without undergoing the type safety checks applied to other input sources. This architectural flaw creates a direct path from unauthenticated webhook requests to arbitrary command execution.

Root Cause

The root cause stems from two interconnected design flaws:

1. Incomplete argument type sanitization: The checkShellArgumentSafety function was designed to validate dangerous argument types but the security review failed to include password-typed arguments in the blocklist, creating an exploitable gap in input validation.

2. Missing type safety for webhook inputs: Webhook-extracted JSON values bypass the type checking mechanisms entirely, violating the security principle that all user-controllable input must be validated before use in security-sensitive operations like shell command execution.

Attack Vector

The vulnerability is exploitable over the network without user interaction. For the first vector, any user with basic authentication (trivially obtainable due to default open registration) can inject shell metacharacters through password-typed arguments. For the second vector, an unauthenticated attacker can craft malicious webhook payloads containing shell metacharacters within JSON values, achieving command execution when OliveTin processes the webhook and passes the unsanitized values to the shell.

The attack exploits the trust boundary between web input and shell execution. When shell metacharacters such as semicolons, backticks, or command substitution syntax are included in either password arguments or webhook JSON values, the sh -c invocation interprets these as command separators or subcommands, leading to arbitrary code execution.

For detailed technical analysis and proof-of-concept information, see the GitHub Security Advisory.

Detection Methods for CVE-2026-27626

Indicators of Compromise

• Unusual process spawning from the OliveTin process with unexpected command arguments
• Webhook requests containing shell metacharacters (;, |, $(), backticks) in JSON values
• Password field submissions with shell metacharacters or command syntax
• Unexpected network connections originating from the OliveTin process
• New user registrations followed by immediate action execution with suspicious parameters

Detection Strategies

• Monitor OliveTin process activity for child processes executing unexpected commands
• Implement webhook payload inspection to detect shell metacharacters in JSON values
• Enable verbose logging on OliveTin and analyze logs for malformed or suspicious input patterns
• Deploy web application firewall rules to block requests containing common command injection patterns
• Review authentication logs for unusual registration patterns or rapid action execution sequences

Monitoring Recommendations

• Configure real-time alerting for any process spawned by OliveTin executing shell commands with unusual syntax
• Implement network traffic analysis on webhook endpoints to detect potential exploitation attempts
• Establish baseline behavior for OliveTin operations and alert on deviations
• Monitor system-level events for privilege escalation or lateral movement following OliveTin process activity

How to Mitigate CVE-2026-27626

Immediate Actions Required

• Disable webhook functionality if not strictly required for operations
• Restrict network access to OliveTin instances using firewall rules or network segmentation
• Disable open registration and change authType from none to a more restrictive authentication mechanism
• Run OliveTin with minimal privileges using a dedicated service account with restricted permissions
• Consider temporarily disabling OliveTin until a patched version becomes available

Patch Information

As of the publication date (2026-02-25), no patched version of OliveTin is available. Organizations should monitor the GitHub Security Advisory for updates regarding a security fix and apply patches immediately when released.

Workarounds

• Deploy a reverse proxy with input validation to filter shell metacharacters from webhook payloads and password fields before they reach OliveTin
• Implement network-level restrictions to limit which external sources can send webhooks to OliveTin
• Avoid using Shell mode with webhook-triggered actions until a patch is available
• Run OliveTin in a containerized environment with strict seccomp profiles and limited capabilities
• Use application-level firewall rules to block known command injection patterns

# Example: Restrict network access to OliveTin with iptables
# Allow only trusted internal network
iptables -A INPUT -p tcp --dport 1337 -s 10.0.0.0/8 -j ACCEPT
iptables -A INPUT -p tcp --dport 1337 -j DROP