> For the complete documentation index, see [llms.txt](https://reports.immunefi.com/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://reports.immunefi.com/zerolend/29069-sc-medium-ability-to-deny-users-from-repaying-and-supplyi....md). # 29069 - \[SC - Medium] Ability to deny users from repaying and supplyi... Submitted on Mar 6th 2024 at 14:21:15 UTC by @OceanAndThunders for [Boost | ZeroLend](https://immunefi.com/bounty/zerolend-boost/) Report ID: #29069 Report type: Smart Contract Report severity: Medium Target: Impacts: * Griefing (e.g. no profit motive for an attacker, but damage to the users or the protocol) ## Description Hello team, ## Brief/Intro The repayWithPermit and supplyWithPermit functions on pool contract "0x54d6F91bE4509826559ad12E1Ca6CA3A6C3811e0" uses the permit function for external ERC20 contract, an attacker can front run the permit function , thus the pool.repayWithPermit and pool.supplyWithPermit will automatically reverts, allows a chain call/transaction all be griefed ## Vulnerability Details The pool contract "0x54d6F91bE4509826559ad12E1Ca6CA3A6C3811e0" allows the user to supply with permit to external contract by providing the permit hash to pool.repayWithPermit, this later will call external token with the given permit bytes, the functions repayWithPermit and supplyWithPermit will revert if the attacker front runs the token.permit with the victim's bytes, the first call will succeed and consumes the nonce, thus the pool.repayWithPermit (the original call) will revert then, the call/transaction will be reverted all the way ## Impact Details Denying users from using the pool.repayWithPermit and pool.supplyWithPermit properly ## References Example explanation of the issue : ## Proof of concept : In this test "" include this line at 411 (as the attacker called the permit before the protocols call usdc.permit) : ``` // extracteting v, r, s from the mempool and calling the usdc.permit before pool.repayWithPermit //the usedc.permit call should succeed, thus it will rsults for the pool.repayWithPermit call failure await usdc.permit(deployer.address,l2Pool.address,amount.toString(),highDeadline,v,r,s); ``` This will makes the function reverts ! Regards, Adam --- # Agent Instructions This documentation is published with GitBook. GitBook is the documentation platform designed so that both humans and AI agents can read, navigate, and reason over technical content effectively. Learn more at gitbook.com. ## Querying This Documentation If you need additional information that is not directly available in this page, you can query the documentation by asking a question. Perform an HTTP GET request on the following URL with the `ask` and `goal` query parameters: ``` GET https://reports.immunefi.com/zerolend/29069-sc-medium-ability-to-deny-users-from-repaying-and-supplyi....md?ask=&goal= ``` `ask` is the immediate question: it should be specific, self-contained, and written in natural language. `goal` is what the user is ultimately trying to achieve, the reason they need the answer. Sharing it helps GitBook give you a better, more relevant answer. A goal is most helpful when it describes the outcome the user wants rather than restating the question. For example, with `ask=how do I create an API token`, a goal like `automate deployments from our CI pipeline` lets GitBook tailor the answer to that use case. The response will contain a direct answer to the question and relevant excerpts and sources from the documentation. Use this mechanism when the answer is not explicitly present in the current page, you need clarification or additional context, or you want to retrieve related documentation sections.