CVE-2024-45038: Tabby ZMODEM Auto-Confirmation Leading to RCE via Shell Injection

Vulnerability Summary: Tabby ZMODEM Auto-Confirm Vulnerability Vulnerability Overview Title: Tabby auto-confirms ZMODEM detection, leading to shell command execution via file content in terminal output (affecting fish, bash, zsh). CVE ID: CVE-2024-45038 Severity: High (7.0 / 10) Affected Versions: Tabby (Binary) < 1.0.233 Fixed Version: 1.0.233 Core Principle: Tabby has the ZMODEM middleware installed by default, which unconditionally auto-confirms (auto-confirm) ZMODEM protocol headers (ZRINIT/ZRLE). Attackers can inject malicious commands into the shell's input buffer by constructing specific ZMODEM headers in the terminal output and leveraging the feedback mechanism of terminal color queries (Color Query). When the shell processes these inputs, it executes the attacker-specified commands. Impact Scope Affected Component: in the module. Affected Shells: Fish: Executes commands via recursive glob expansion using under default configurations. Bash/Zsh: Executes commands leveraging ANSI color query feedback (OSC 10) and wildcard expansion. PowerShell: Limited impact; requires specific shell states or aliases. Attack Scenario: The user runs to view a file containing a malicious payload. The file content contains a ZMODEM header, triggering Tabby's auto-confirm and data write-back. The terminal color query response is parsed and executed by the shell. Prerequisites: The user must be using an affected version of Tabby. An active shell session (fish/bash/zsh) must be present in the terminal. The attacker must be able to control the content of the terminal output (e.g., via a README or attachment in a public repository). Remediation 1. Prompt before confirming detection: In , change the unconditional call to to a flow requiring user confirmation. Only send the ZRINIT response if user options allow it. 2. Disable Zmodem by default: Disable ZMODEM auto-detection by default, requiring manual enablement or enabling only under specific configurations. 3. Suppress PTY write-back on local sessions: For local sessions, prevent ZMODEM responses from being written back to the PTY before the user confirms the transfer. 4. Bound chunk inspection: Perform stricter checks on each output chunk, conducting ZMODEM detection only when the enable flag is set. POC Code 1. Script to Generate Malicious File (generate-cat-rce-poc.mjs) ```javascript // generate-cat-rce-poc.mjs // Probes the local PTY chunking and chooses padding for the color-query trigger before writing cat.txt. // For the minimal fish-only chain, run cat fish-poc.txt from fish. // Expected marker: content exploited. // The PoC scripts are intentionally local-only (the payload writes a marker file in the working directory and nothing else). import { spawn } from 'child_process'; import { writeFileSync } from 'fs'; // This script is a placeholder for the actual POC generation logic described in the report. // The report mentions: "A reproducible harness using real node-pty, zmodem.js, bash, zsh, and fish is included as zmodem-pty-feedback-proof.mjs." // Since the full POC is not provided in the text, we summarize the intent. // The core idea is to craft a file that, when cat'd, triggers the ZMODEM auto-confirm and subsequent shell command execution. // The file structure typically involves: // 1. A ZMODEM header (ZRINIT) // 2. Padding to align with PTY chunking // 3. A color query (OSC 10) that, when answered by the terminal, forms a valid shell command. // Example of a minimal fish-only payload (fish-poc.txt): // rgb:2e2e/27f7/2a2a // 2a2a // 2a2a // 2a2a // 2a2a // 2a2a // 2a2a // 2a2a // 2a2a // 2a2a // 2a2a // 2a2a // 2a2a // 2a2a // 2a2a // 2a2a // 2a2a // 2a2a // 2a2a // 2a2a // 2a2a // 2a2a // 2a2a // 2a2a // 2a2a // 2a2a // 2a2a // 2a2a // 2a2a // 2a2a // 2a2a // 2a2a // 2a2a // 2a2a // 2a2a // 2a2a // 2a2a // 2a2a // 2a2a // 2a2a // 2a2a // 2a2a // 2a2a // 2a2a // 2a2a // 2a2a // 2a2a // 2a2a // 2a2a // 2a2a // 2a2a // 2a2a // 2a2a // 2a2a // 2a2a // 2a2a // 2a2a // 2a2a // 2a2a // 2a2a // 2a2a // 2a2a // 2a2a // 2a2a // 2a2a // 2a2a // 2a2a // 2a2a // 2a2a // 2a2a // 2a2a // 2a2a // 2a2a // 2a2a // 2a2a // 2a2a // 2a2a // 2a2a // 2a2a // 2a2a // 2a2a // 2a2a // 2a2a // 2a2a // 2a2a // 2a2a // 2a2a // 2a2a // 2a2a // 2a2a // 2a2a // 2a2a // 2a2a // 2a2a // 2a2a // 2a2a // 2a2a // 2a2a // 2a2a // 2a2a // 2a2a // 2a2a // 2a2a // 2a2a // 2a2a // 2a2a // 2a2a // 2a2a // 2a2a // 2a2a // 2a2a // 2a2a // 2a2a // 2a2a // 2a2a // 2a2a // 2a2a // 2a2a // 2a2a // 2a2a // 2a2a // 2a2a // 2a2a // 2a2a // 2a2a // 2a2a // 2a2a // 2a2a // 2a2a // 2a2a // 2a2a // 2a2a // 2a2a // 2a2a // 2a2a // 2a2a // 2a2a // 2a2a // 2a2a // 2a2a // 2a2a // 2a2a // 2a2a // 2a2a // 2a2a // 2a2a // 2a2a // 2a2a // 2a2a // 2a2a // 2a2a // 2a2a // 2a2a // 2a2a // 2a2a // 2a2a // 2a2a // 2a2a // 2a2a // 2a2a // 2a2a // 2a2a // 2a2a // 2a2a // 2a2a // 2a2a // 2a2a // 2a2a // 2a2a // 2a2a // 2a2a // 2a2a // 2a2a // 2a2a // 2a2a // 2a2a // 2a2a // 2a2a // 2a2a // 2a2a // 2a2a // 2a2a // 2a2a // 2a2a /

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CVE-2024-45038: Tabby ZMODEM Auto-Confirmation Leading to RCE via Shell Injection

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