# Do Reentrancy Guards Protect against Both Single-Function and Cross-Function Attacks? ⎊ Path

**Published:** 2025-12-04
**Author:** Greeks.live
**Categories:** Path

---

## Do Reentrancy Guards Protect against Both Single-Function and Cross-Function Attacks?

Yes, a properly implemented reentrancy guard can protect against both types of attacks. The guard typically uses a lock that is applied at the contract level, not just for a single function.

When any function with the guard modifier is entered, the lock is activated. If an external call from this function leads to a re-entrant call to any other function that also has the guard, the second function will see the lock is active and will revert the transaction.

This prevents both recursive calls to the same function and calls to other state-sharing functions within the contract.

- [What Is a ‘Reentrancy Attack’?](https://learn.greeks.live/path/what-is-a-reentrancy-attack/)

- [Can This Attack Be Prevented by Using a Non-Reentrant Lock?](https://learn.greeks.live/path/can-this-attack-be-prevented-by-using-a-non-reentrant-lock/)

- [How Can a Time-Lock Smart Contract Be Used to Prevent the Immediate Withdrawal of LP Tokens?](https://learn.greeks.live/path/how-can-a-time-lock-smart-contract-be-used-to-prevent-the-immediate-withdrawal-of-lp-tokens/)

- [What Is a “Reentrancy Attack” in Smart Contract Security?](https://learn.greeks.live/path/what-is-a-reentrancy-attack-in-smart-contract-security/)

- [What Is the Role of a Fallback Function in Facilitating a Reentrancy Attack?](https://learn.greeks.live/path/what-is-the-role-of-a-fallback-function-in-facilitating-a-reentrancy-attack/)

- [How Does the Nonreentrant Modifier Implement the CEI Principle?](https://learn.greeks.live/path/how-does-the-nonreentrant-modifier-implement-the-cei-principle/)

- [How Can Reentrancy Attacks Be Prevented in Smart Contracts?](https://learn.greeks.live/path/how-can-reentrancy-attacks-be-prevented-in-smart-contracts/)

- [Can a Reentrancy Attack Be Performed without a Fallback Function?](https://learn.greeks.live/path/can-a-reentrancy-attack-be-performed-without-a-fallback-function/)

## Glossar

### [Reentrancy Guard Modifier](https://learn.greeks.live/area/reentrancy-guard-modifier/?utm_source=crypto.greeks.live&utm_medium=referral&utm_campaign=satellite)

Mechanism ⎊ A Reentrancy Guard Modifier functions as a critical control within smart contract architecture, specifically designed to prevent malicious recursive calls during function execution.

### [Reentrancy Guard](https://learn.greeks.live/area/reentrancy-guard/?utm_source=crypto.greeks.live&utm_medium=referral&utm_campaign=satellite)

Mitigation ⎊ A Reentrancy Guard functions as a critical control mechanism within smart contracts, specifically designed to prevent recursive calls to the same function before the initial execution completes.

### [Reentrancy Guards](https://learn.greeks.live/area/reentrancy-guards/?utm_source=crypto.greeks.live&utm_medium=referral&utm_campaign=satellite)

Mechanism ⎊ Reentrancy Guards are specialized code mechanisms, typically implemented as function modifiers, that enforce a mutual exclusion lock on a smart contract function during its execution.

## Discover More

### [How Does the Index Price Composition Protect against Single-Source Manipulation and Failure?](https://learn.greeks.live/path/how-does-the-index-price-composition-protect-against-single-source-manipulation-and-failure/?utm_source=crypto.greeks.live&utm_medium=referral&utm_campaign=satellite)
![How Does the Index Price Composition Protect against Single-Source Manipulation and Failure?](https://learn.greeks.live/wp-content/uploads/2025/10/Intersecting-Translucent-Hedging-Vectors-Over-Centralized-Decentralized-Finance-Wheel-Mechanism.webp)

It averages the spot price from multiple major exchanges, diluting the impact of any single source's failure.

### [How Does a Reentrancy Attack Relate to the DAO Hack?](https://learn.greeks.live/path/how-does-a-reentrancy-attack-relate-to-the-dao-hack/?utm_source=crypto.greeks.live&utm_medium=referral&utm_campaign=satellite)
![How Does a Reentrancy Attack Relate to the DAO Hack?](https://learn.greeks.live/wp-content/uploads/2025/10/Quantum-Entanglement-Calibration-of-Digital-Asset-Tokenization-Utilizing-Synthetic-Option-Strike-Price-Probes.webp)

The DAO hack was the seminal event where Reentrancy was exploited to drain Ether before the balance was updated.

### [How Can a Reentrancy Guard Modifier Offer a Simpler Alternative to This Pattern?](https://learn.greeks.live/path/how-can-a-reentrancy-guard-modifier-offer-a-simpler-alternative-to-this-pattern/?utm_source=crypto.greeks.live&utm_medium=referral&utm_campaign=satellite)
![How Can a Reentrancy Guard Modifier Offer a Simpler Alternative to This Pattern?](https://learn.greeks.live/wp-content/uploads/2025/10/Symmetrical-Abstract-Representation-of-Bifurcated-Opciones-Execution-Dynamics-in-Digital-Asset-Swaps.webp)

A reentrancy guard uses a lock to ensure a function cannot be re-entered until its first execution is complete.

### [How Did the DAO Hack Use a Reentrancy Vulnerability?](https://learn.greeks.live/path/how-did-the-dao-hack-use-a-reentrancy-vulnerability/?utm_source=crypto.greeks.live&utm_medium=referral&utm_campaign=satellite)
![How Did the DAO Hack Use a Reentrancy Vulnerability?](https://learn.greeks.live/wp-content/uploads/2025/10/Xray-Visualization-of-a-Decentralized-Autonomous-Organization-Governance-Rotor-Mechanism-Rotation-Dynamics.webp)

The DAO hacker repeatedly called the withdrawal function, draining funds before the contract could update its own balance to reflect the withdrawals.

### [How Can Options Strategies, Such as a Straddle or Strangle, Be Used to Protect against Impermanent Loss from High Volatility in Either Direction?](https://learn.greeks.live/path/how-can-options-strategies-such-as-a-straddle-or-strangle-be-used-to-protect-against-impermanent-loss-from-high-volatility-in-either-direction/?utm_source=crypto.greeks.live&utm_medium=referral&utm_campaign=satellite)
![How Can Options Strategies, Such as a Straddle or Strangle, Be Used to Protect against Impermanent Loss from High Volatility in Either Direction?](https://learn.greeks.live/wp-content/uploads/2025/10/Asymmetrical-Convergence-of-Microstructure-Reflecting-Decentralized-Exchange-Liquidity-Pools.webp)

Buying a call and put option (a straddle/strangle) creates a profit from high volatility, which can be used to offset impermanent loss.

### [What Security Vulnerability Is Associated with "Reentrancy" in Smart Contracts?](https://learn.greeks.live/path/what-security-vulnerability-is-associated-with-reentrancy-in-smart-contracts/?utm_source=crypto.greeks.live&utm_medium=referral&utm_campaign=satellite)
![What Security Vulnerability Is Associated with "Reentrancy" in Smart Contracts?](https://learn.greeks.live/wp-content/uploads/2025/10/Crystalline-Bifurcation-Balancing-Volatile-Digital-Asset-Swaption-Payoffs-Across-Impermanent-Loss-Vectors.webp)

External call recursively calls back; Allows repeated fund draining; Exploited in the DAO hack.

### [What Is a Circuit Breaker Mechanism and How Does It Protect against Slow-Burn Attacks?](https://learn.greeks.live/path/what-is-a-circuit-breaker-mechanism-and-how-does-it-protect-against-slow-burn-attacks/?utm_source=crypto.greeks.live&utm_medium=referral&utm_campaign=satellite)
![What Is a Circuit Breaker Mechanism and How Does It Protect against Slow-Burn Attacks?](https://learn.greeks.live/wp-content/uploads/2025/10/Precision-Assembly-of-Modular-Blockchain-Substrates-Securing-Critical-Execution-Points-in-Decentralized-Finance-Architectures.webp)

An automated safety feature that halts trading or liquidations if the price deviates excessively from a reference, stopping malicious execution.

### [How Do Withdrawal Limits Function as a Secondary Defense against Successful Attacks?](https://learn.greeks.live/path/how-do-withdrawal-limits-function-as-a-secondary-defense-against-successful-attacks/?utm_source=crypto.greeks.live&utm_medium=referral&utm_campaign=satellite)
![How Do Withdrawal Limits Function as a Secondary Defense against Successful Attacks?](https://learn.greeks.live/wp-content/uploads/2025/10/Abstract-Visualization-of-Colliding-Liquidity-Pools-and-Gamma-Hedging-Mechanisms-in-DeFi-Derivatives.webp)

Limits restrict the total value an attacker can immediately withdraw after a successful double-spend, mitigating the total loss.

### [How Do Margin Calls Protect the Solvency of a Derivatives Exchange during Volatile Market Conditions?](https://learn.greeks.live/path/how-do-margin-calls-protect-the-solvency-of-a-derivatives-exchange-during-volatile-market-conditions/?utm_source=crypto.greeks.live&utm_medium=referral&utm_campaign=satellite)
![How Do Margin Calls Protect the Solvency of a Derivatives Exchange during Volatile Market Conditions?](https://learn.greeks.live/wp-content/uploads/2025/10/Decentralized-Exchange-Mechanism-Core-Component-Modeling-for-Volatility-Surface-Calibration-in-DeFi-Options.webp)

Margin calls force traders to post more collateral or face liquidation, preventing losses from exceeding their margin and protecting the exchange's capital.

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**Original URL:** https://learn.greeks.live/learn/do-reentrancy-guards-protect-against-both-single-function-and-cross-function-attacks/
