Unicode < 14.0.0 - Code Injection via Bidirectional Algorithm Control Sequences
Title source: llmExploitation Summary
EIP tracks 8 public exploits for CVE-2021-42574. PoCs published by simplylu, maweil, tin-z.
AI-analyzed exploit summary This repository provides a tool to generate malicious code using the Trojan Source vulnerability (CVE-2021-42574), which exploits Unicode bidirectional control characters to visually reorder source code. The tool can encode and decode files with these characters, demonstrating how adversaries can hide malicious logic from human reviewers.
Description
An issue was discovered in the Bidirectional Algorithm in the Unicode Specification through 14.0. It permits the visual reordering of characters via control sequences, which can be used to craft source code that renders different logic than the logical ordering of tokens ingested by compilers and interpreters. Adversaries can leverage this to encode source code for compilers accepting Unicode such that targeted vulnerabilities are introduced invisibly to human reviewers. NOTE: the Unicode Consortium offers the following alternative approach to presenting this concern. An issue is noted in the nature of international text that can affect applications that implement support for The Unicode Standard and the Unicode Bidirectional Algorithm (all versions). Due to text display behavior when text includes left-to-right and right-to-left characters, the visual order of tokens may be different from their logical order. Additionally, control characters needed to fully support the requirements of bidirectional text can further obfuscate the logical order of tokens. Unless mitigated, an adversary could craft source code such that the ordering of tokens perceived by human reviewers does not match what will be processed by a compiler/interpreter/etc. The Unicode Consortium has documented this class of vulnerability in its document, Unicode Technical Report #36, Unicode Security Considerations. The Unicode Consortium also provides guidance on mitigations for this class of issues in Unicode Technical Standard #39, Unicode Security Mechanisms, and in Unicode Standard Annex #31, Unicode Identifier and Pattern Syntax. Also, the BIDI specification allows applications to tailor the implementation in ways that can mitigate misleading visual reordering in program text; see HL4 in Unicode Standard Annex #9, Unicode Bidirectional Algorithm.
Exploits (8)
This repository provides a tool to generate malicious code using the Trojan Source vulnerability (CVE-2021-42574), which exploits Unicode bidirectional control characters to visually reorder source code. The tool can encode and decode files with these characters, demonstrating how adversaries can hide malicious logic from human reviewers.
This repository provides a Rust-based tool to detect Unicode BIDI characters in files, which can be exploited for supply chain attacks as described in CVE-2021-42574. It includes a Docker container for easy deployment and configuration options for file scanning.
This PoC demonstrates CVE-2021-42574, a trojan source vulnerability in Solidity where Unicode control characters (RLO_i) manipulate code interpretation, causing hidden logic execution. The exploit generates a Solidity contract with deceptive comments that appear benign but compile malicious logic.
This PoC demonstrates CVE-2021-42574, a Trojan Source vulnerability in Rust (pre-1.56.0) using bidirectional Unicode characters to alter code logic during compilation. The example shows how hidden control characters can change conditional logic to bypass access checks.
This repository contains a README file referencing CVE-2021-42574 and CVE-2021-42694 but lacks any exploit code or technical details. It appears to be a placeholder or informational writeup.
This PoC demonstrates a Unicode-based authentication bypass vulnerability (CVE-2021-42574) by exploiting bidirectional override characters to manipulate string comparison logic. The Rust code shows how an attacker could bypass access control checks by crafting a malicious string that appears as 'user' but contains hidden Unicode characters.
This repository provides a tool called 'bidi-guard' that scans code for invisible bidirectional Unicode characters, which can be used in Trojan Source attacks (CVE-2021-42574). It includes functionality to detect, explain, and remove such characters, as well as integrate with CI pipelines and pre-commit hooks.
This repository provides a GitHub Action and Python script to detect Unicode control characters, specifically targeting CVE-2021-42574 (Trojan Source attacks). It scans source files for bidirectional or non-printable Unicode characters that could be used to manipulate code interpretation.
References (18)
Scores
CVSS:3.1/AV:N/AC:H/PR:N/UI:R/S:C/C:H/I:H/A:H