Slither, the smart contract static analyzer

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Slither is a Solidity & Vyper static analysis framework written in Python3. It runs a suite of vulnerability detectors, prints visual information about contract details, and provides an API to easily write custom analyses. Slither enables developers to find vulnerabilities, enhance their code comprehension, and quickly prototype custom analyses.

• Features
• Usage
• How to install
  • Using Pip
  • Using Git
  • Using Docker
  • Integration
• Detectors
• Printers
  • Quick Review Printers
  • In-Depth Review Printers
• Tools
• API Documentation
• Getting Help
• FAQ
• License
• Publications
  • Trail of Bits publication
  • External publications

Features

• Detects vulnerable Solidity code with low false positives (see the list of trophies)
• Identifies where the error condition occurs in the source code
• Easily integrates into continuous integration and Hardhat/Foundry builds
• Built-in 'printers' quickly report crucial contract information
• Detector API to write custom analyses in Python
• Ability to analyze contracts written with Solidity >= 0.4
• Intermediate representation (SlithIR) enables simple, high-precision analyses
• Correctly parses 99.9% of all public Solidity code
• Average execution time of less than 1 second per contract
• Integrates with Github's code scanning in CI
• Support for Vyper smart contracts

Usage

Run Slither on a Hardhat/Foundry/Dapp/Brownie application:

console slither .

This is the preferred option if your project has dependencies as Slither relies on the underlying compilation framework to compile source code.

However, you can run Slither on a single file that does not import dependencies:

console slither tests/uninitialized.sol

How to install

Note
Slither requires Python 3.8+. If you're not going to use one of the supported compilation frameworks, you need solc, the Solidity compiler; we recommend using solc-select to conveniently switch between solc versions.

Using Pip

console python3 -m pip install slither-analyzer

How to upgrade

console python3 -m pip install --upgrade slither-analyzer

Using Brew

console brew install slither-analyzer

Using Git

bash git clone https://github.com/crytic/slither.git && cd slither python3 -m pip install .

We recommend using a Python virtual environment, as detailed in the Developer Installation Instructions, if you prefer to install Slither via git.

Using Docker

Use the eth-security-toolbox docker image. It includes all of our security tools and every major version of Solidity in a single image. /home/share will be mounted to /share in the container.

bash docker pull trailofbits/eth-security-toolbox

To share a directory in the container:

bash docker run -it -v /home/share:/share trailofbits/eth-security-toolbox

Integration

• For GitHub action integration, use slither-action.
• For pre-commit integration, use (replace $GIT_TAG with real tag) ```YAML
  • repo: https://github.com/crytic/slither rev: $GIT_TAG hooks:
    • id: slither ```
• To generate a Markdown report, use slither [target] --checklist.
• To generate a Markdown with GitHub source code highlighting, use slither [target] --checklist --markdown-root https://github.com/ORG/REPO/blob/COMMIT/ (replace ORG, REPO, COMMIT)

Detectors

Num | Detector | What it Detects | Impact | Confidence --- | --- | --- | --- | --- 1 | abiencoderv2-array | Storage abiencoderv2 array | High | High 2 | arbitrary-send-erc20 | transferFrom uses arbitrary from | High | High 3 | array-by-reference | Modifying storage array by value | High | High 4 | encode-packed-collision | ABI encodePacked Collision | High | High 5 | incorrect-shift | The order of parameters in a shift instruction is incorrect. | High | High 6 | multiple-constructors | Multiple constructor schemes | High | High 7 | name-reused | Contract's name reused | High | High 8 | protected-vars | Detected unprotected variables | High | High 9 | public-mappings-nested | Public mappings with nested variables | High | High 10 | rtlo | Right-To-Left-Override control character is used | High | High 11 | shadowing-state | State variables shadowing | High | High 12 | suicidal | Functions allowing anyone to destruct the contract | High | High 13 | uninitialized-state | Uninitialized state variables | High | High 14 | uninitialized-storage | Uninitialized storage variables | High | High 15 | unprotected-upgrade | Unprotected upgradeable contract | High | High 16 | codex | Use Codex to find vulnerabilities. | High | Low 17 | arbitrary-send-erc20-permit | transferFrom uses arbitrary from with permit | High | Medium 18 | arbitrary-send-eth | Functions that send Ether to arbitrary destinations | High | Medium 19 | controlled-array-length | Tainted array length assignment | High | Medium 20 | controlled-delegatecall | Controlled delegatecall destination | High | Medium 21 | delegatecall-loop | Payable functions using delegatecall inside a loop | High | Medium 22 | incorrect-exp | Incorrect exponentiation | High | Medium 23 | incorrect-return | If a return is incorrectly used in assembly mode. | High | Medium 24 | msg-value-loop | msg.value inside a loop | High | Medium 25 | reentrancy-eth | Reentrancy vulnerabilities (theft of ethers) | High | Medium 26 | return-leave | If a return is used instead of a leave. | High | Medium 27 | storage-array | Signed storage integer array compiler bug | High | Medium 28 | unchecked-transfer | Unchecked tokens transfer | High | Medium 29 | weak-prng | Weak PRNG | High | Medium 30 | domain-separator-collision | Detects ERC20 tokens that have a function whose signature collides with EIP-2612's DOMAIN_SEPARATOR() | Medium | High 31 | enum-conversion | Detect dangerous enum conversion | Medium | High 32 | erc20-interface | Incorrect ERC20 interfaces | Medium | High 33 | erc721-interface | Incorrect ERC721 interfaces | Medium | High 34 | incorrect-equality | Dangerous strict equalities | Medium | High 35 | locked-ether | Contracts that lock ether | Medium | High 36 | mapping-deletion | Deletion on mapping containing a structure | Medium | High 37 | pyth-deprecated-functions | Detect Pyth deprecated functions | Medium | High 38 | pyth-unchecked-confidence | Detect when the confidence level of a Pyth price is not checked | Medium | High 39 | pyth-unchecked-publishtime | Detect when the publishTime of a Pyth price is not checked | Medium | High 40 | shadowing-abstract | State variables shadowing from abstract contracts | Medium | High 41 | tautological-compare | Comparing a variable to itself always returns true or false, depending on comparison | Medium | High 42 | tautology | Tautology or contradiction | Medium | High 43 | write-after-write | Unused write | Medium | High 44 | boolean-cst | Misuse of Boolean constant | Medium | Medium 45 | chronicle-unchecked-price | Detect when Chronicle price is not checked. | Medium | Medium 46 | constant-function-asm | Constant functions using assembly code | Medium | Medium 47 | constant-function-state | Constant functions changing the state | Medium | Medium 48 | divide-before-multiply | Imprecise arithmetic operations order | Medium | Medium 49 | gelato-unprotected-randomness | Call to _requestRandomness within an unprotected function | Medium | Medium 50 | out-of-order-retryable | Out-of-order retryable transactions | Medium | Medium 51 | reentrancy-no-eth | Reentrancy vulnerabilities (no theft of ethers) | Medium | Medium 52 | reused-constructor | Reused base constructor | Medium | Medium 53 | tx-origin | Dangerous usage of tx.origin | Medium | Medium 54 | unchecked-lowlevel | Unchecked low-level calls | Medium | Medium 55 | unchecked-send | Unchecked send | Medium | Medium 56 | uninitialized-local | Uninitialized local variables | Medium | Medium 57 | unused-return | Unused return values | Medium | Medium 58 | chainlink-feed-registry | Detect when chainlink feed registry is used | Low | High 59 | incorrect-modifier | Modifiers that can return the default value | Low | High 60 | optimism-deprecation | Detect when deprecated Optimism predeploy or function is used. | Low | High 61 | shadowing-builtin | Built-in symbol shadowing | Low | High 62 | shadowing-local | Local variables shadowing | Low | High 63 | uninitialized-fptr-cst | Uninitialized function pointer calls in constructors | Low | High 64 | variable-scope | Local variables used prior their declaration | Low | High 65 | void-cst | Constructor called not implemented | Low | High 66 | calls-loop | Multiple calls in a loop | Low | Medium 67 | events-access | Missing Events Access Control | Low | Medium 68 | events-maths | Missing Events Arithmetic | Low | Medium 69 | incorrect-unary | Dangerous unary expressions | Low | Medium 70 | missing-zero-check | Missing Zero Address Validation | Low | Medium 71 | reentrancy-benign | Benign reentrancy vulnerabilities | Low | Medium 72 | reentrancy-events | Reentrancy vulnerabilities leading to out-of-order Events | Low | Medium 73 | return-bomb | A low level callee may consume all callers gas unexpectedly. | Low | Medium 74 | timestamp | Dangerous usage of block.timestamp | Low | Medium 75 | assembly | Assembly usage | Informational | High 76 | assert-state-change | Assert state change | Informational | High 77 | boolean-equal | Comparison to boolean constant | Informational | High 78 | cyclomatic-complexity | Detects functions with high (> 11) cyclomatic complexity | Informational | High 79 | deprecated-standards | Deprecated Solidity Standards | Informational | High 80 | erc20-indexed | Un-indexed ERC20 event parameters | Informational | High 81 | function-init-state | Function initializing state variables | Informational | High 82 | incorrect-using-for | Detects using-for statement usage when no function from a given library matches a given type | Informational | High 83 | low-level-calls | Low level calls | Informational | High 84 | missing-inheritance | Missing inheritance | Informational | High 85 | naming-convention | Conformity to Solidity naming conventions | Informational | High 86 | pragma | If different pragma directives are used | Informational | High 87 | redundant-statements | Redundant statements | Informational | High 88 | solc-version | Incorrect Solidity version | Informational | High 89 | unimplemented-functions | Unimplemented functions | Informational | High 90 | unused-state | Unused state variables | Informational | High 91 | costly-loop | Costly operations in a loop | Informational | Medium 92 | dead-code | Functions that are not used | Informational | Medium 93 | reentrancy-unlimited-gas | Reentrancy vulnerabilities through send and transfer | Informational | Medium 94 | too-many-digits | Conformance to numeric notation best practices | Informational | Medium 95 | cache-array-length | Detects for loops that use length member of some storage array in their loop condition and don't modify it. | Optimization | High 96 | constable-states | State variables that could be declared constant | Optimization | High 97 | external-function | Public function that could be declared external | Optimization | High 98 | immutable-states | State variables that could be declared immutable | Optimization | High 99 | var-read-using-this | Contract reads its own variable using this | Optimization | High

For more information, see

• The Detector Documentation for details on each detector
• The Detection Selection to run only selected detectors. By default, all the detectors are run.
• The Triage Mode to filter individual results

Printers

Quick Review Printers

• human-summary: Print a human-readable summary of the contracts
• inheritance-graph: Export the inheritance graph of each contract to a dot file
• contract-summary: Print a summary of the contracts
• loc: Count the total number lines of code (LOC), source lines of code (SLOC), and comment lines of code (CLOC) found in source files (SRC), dependencies (DEP), and test files (TEST).
• entry-points: Print all the state-changing entry point functions of the contracts

In-Depth Review Printers

• call-graph: Export the call-graph of the contracts to a dot file
• cfg: Export the CFG of each functions
• function-summary: Print a summary of the functions
• vars-and-auth: Print the state variables written and the authorization of the functions
• not-pausable: Print functions that do not use whenNotPaused modifier.

To run a printer, use --print and a comma-separated list of printers.

See the Printer documentation for the complete lists.

Tools

• slither-check-upgradeability: Review delegatecall-based upgradeability
• slither-prop: Automatic unit test and property generation
• slither-flat: Flatten a codebase
• slither-check-erc: Check the ERC's conformance
• slither-read-storage: Read storage values from contracts
• slither-interface: Generate an interface for a contract

See the Tool documentation for additional tools.

Contact us to get help on building custom tools.

API Documentation

Documentation on Slither's internals is available here.

Getting Help

Feel free to stop by our Slack channel (#ethereum) for help using or extending Slither.

• The Printer documentation describes the information Slither is capable of visualizing for each contract.

• The Detector documentation describes how to write a new vulnerability analyses.

• The API documentation describes the methods and objects available for custom analyses.

• The SlithIR documentation describes the SlithIR intermediate representation.

FAQ

How do I exclude mocks or tests?

• View our documentation on path filtering.

How do I fix "unknown file" or compilation issues?

• Because slither requires the solc AST, it must have all dependencies available. If a contract has dependencies, slither contract.sol will fail. Instead, use slither . in the parent directory of contracts/ (you should see contracts/ when you run ls). If you have a node_modules/ folder, it must be in the same directory as contracts/. To verify that this issue is related to slither, run the compilation command for the framework you are using e.g npx hardhat compile. That must work successfully; otherwise, slither's compilation engine, crytic-compile, cannot generate the AST.

License

Slither is licensed and distributed under the AGPLv3 license. Contact us if you're looking for an exception to the terms.

Publications

Trail of Bits publication

• Slither: A Static Analysis Framework For Smart Contracts, Josselin Feist, Gustavo Grieco, Alex Groce - WETSEB '19

External publications

Title | Usage | Authors | Venue | Code --- | --- | --- | --- | --- ReJection: A AST-Based Reentrancy Vulnerability Detection Method | AST-based analysis built on top of Slither | Rui Ma, Zefeng Jian, Guangyuan Chen, Ke Ma, Yujia Chen | CTCIS 19 | - MPro: Combining Static and Symbolic Analysis for Scalable Testing of Smart Contract | Leverage data dependency through Slither | William Zhang, Sebastian Banescu, Leodardo Pasos, Steven Stewart, Vijay Ganesh | ISSRE 2019 | MPro ETHPLOIT: From Fuzzing to Efficient Exploit Generation against Smart Contracts | Leverage data dependency through Slither | Qingzhao Zhang, Yizhuo Wang, Juanru Li, Siqi Ma | SANER 20 | - Verification of Ethereum Smart Contracts: A Model Checking Approach | Symbolic execution built on top of Slithers CFG | Tam Bang, Hoang H Nguyen, Dung Nguyen, Toan Trieu, Tho Quan | IJMLC 20 | - Smart Contract Repair | Rely on Slithers vulnerabilities detectors | Xiao Liang Yu, Omar Al-Bataineh, David Lo, Abhik Roychoudhury | TOSEM 20 | SCRepair Demystifying Loops in Smart Contracts | Leverage data dependency through Slither | Ben Mariano, Yanju Chen, Yu Feng, Shuvendu Lahiri, Isil Dillig | ASE 20 | - Trace-Based Dynamic Gas Estimation of Loops in Smart Contracts | Use Slithers CFG to detect loops | Chunmiao Li, Shijie Nie, Yang Cao, Yijun Yu, Zhenjiang Hu | IEEE Open J. Comput. Soc. 1 (2020) | - SAILFISH: Vetting Smart Contract State-Inconsistency Bugs in Seconds | Rely on SlithIR to build a storage dependency graph | Priyanka Bose, Dipanjan Das, Yanju Chen, Yu Feng, Christopher Kruegel, and Giovanni Vigna | S&P 22 | Sailfish SolType: Refinement Types for Arithmetic Overflow in Solidity | Use Slither as frontend to build refinement type system | Bryan Tan, Benjamin Mariano, Shuvendu K. Lahiri, Isil Dillig, Yu Feng | POPL 22 | - Do Not Rug on Me: Leveraging Machine Learning Techniques for Automated Scam Detection | Use Slither to extract tokens' features (mintable, pausable, ..) | Mazorra, Bruno, Victor Adan, and Vanesa Daza | Mathematics 10.6 (2022) | - MANDO: Multi-Level Heterogeneous Graph Embeddings for Fine-Grained Detection of Smart Contract Vulnerabilities | Use Slither to extract the CFG and call graph | Hoang Nguyen, Nhat-Minh Nguyen, Chunyao Xie, Zahra Ahmadi, Daniel Kudendo, Thanh-Nam Doan and Lingxiao Jiang| IEEE 9th International Conference on Data Science and Advanced Analytics (DSAA, 2022) | ge-sc Automated Auditing of Price Gouging TOD Vulnerabilities in Smart Contracts | Use Slither to extract the CFG and data dependencies| Sidi Mohamed Beillahi, Eric Keilty, Keerthi Nelaturu, Andreas Veneris, and Fan Long | 2022 IEEE International Conference on Blockchain and Cryptocurrency (ICBC) | Smart-Contract-Repair Modeling and Enforcing Access Control Policies for Smart Contracts | Extend Slither's data dependencies | Jan-Philipp Toberg, Jonas Schiffl, Frederik Reiche, Bernhard Beckert, Robert Heinrich, Ralf Reussner | IEEE International Conference on Decentralized Applications and Infrastructures (DAPPS), 2022 | SolidityAccessControlEnforcement Smart Contract Vulnerability Detection Based on Deep Learning and Multimodal Decision Fusion | Use Slither to extract the CFG | Weichu Deng, Huanchun Wei, Teng Huang, Cong Cao, Yun Peng, and Xuan Hu | Sensors 2023, 23, 7246 | - Semantic-enriched Code Knowledge Graph to Reveal Unknowns in Smart Contract Code Reuse | Use Slither to extract the code features (CFG, function, parameters types, ..) | Qing Huang, Dianshu Liao, Zhenchang Xing, Zhengkang Zuo, Changjing Wang, Xin Xia | ACM Transactions on Software Engineering and Methodology, 2023 | - Smart Contract Parallel Execution with Fine-Grained State Accesses | Use Slither to build state access graphs | Xiaodong Qi, Jiao Jiao, Yi Li | International Conference on Distributed Computing Systems (ICDCS), 2023 | - Bad Apples: Understanding the Centralized Security Risks in Decentralized Ecosystems | Implement an internal analysis on top of Slither | Kailun Yan , Jilian Zhang , Xiangyu Liu , Wenrui Diao , Shanqing Guo | ACM Web Conference April 2023 | - Identifying Vulnerabilities in Smart Contracts using Interval Analysis | Create 4 detectors on top of Slither | tefan-Claudiu Susan, Andrei Arusoaie | FROM 2023 | - Storage State Analysis and Extraction of Ethereum Blockchain Smart Contracts (no PDF in open access) | Rely on Slither's CFG and AST | Maha Ayub , Tania Saleem , Muhammad Janjua , Talha Ahmad | TOSEM 2023 | SmartMuv

If you are using Slither on an academic work, consider applying to the Crytic $10k Research Prize.