How much was lost in the TenderFi hack?

The TenderFi hack resulted in $1.6M in losses on March 07, 2023.

What attack technique was used in the TenderFi exploit?

The TenderFi exploit utilized Oracle Issue. Understanding this attack vector is critical for smart contract auditors and developers building secure DeFi protocols.

How can developers prevent similar smart contract attacks?

Preventing smart contract hacks requires a combination of secure coding practices, thorough security audits, and understanding common attack vectors like reentrancy, oracle manipulation, and access control flaws. Smart Contract Hacking (SCH) provides hands-on training to help developers and auditors identify and prevent vulnerabilities before deployment.

TenderFi Hack

TOTAL LOST $1.6M

Medium Mar 07, 2023 Oracle Issue

Affected Chain 2023 Incident surface

Recovered $1.5M 93.9% returned

All-Time Rank #725 By amount stolen

Auditors 2 Prior security audits

Incident Overview

Quick Summary

TenderFi was exploited by a WhiteHat hacker via the Oracle issue. The hacker was able to borrow 1,583,432 $USD worth of assets and returned almost the full amount.

Details of the Exploit

TenderFi is a Lending and Borrowing protocol running on the layer-2 Arbitrum chain. The protocol was exploited via Oracle issue, which allowed the hacker to take 1,583,432 $USD worth of assets for 1 $GMX (~70 $USD). The project's Unitroller contract has oracle misconfiguration, which allowed malicious actions on DistributedBorrowerComp() function.

The WhiteHat hacker left an on-chain message, to contact him to return the funds. Within 24 hours after the incident, the TenderFi Team was able to recover the funds, while paying the Bug Bounty for 62.15 $ETH. The received funds were transferred to another EOA address.

The TenderFi Team claimed they will compensate the remaining funds, so the protocol's users will not be affected and there will be no bad debt.

Block Data Reference

Attacker address:

https://arbiscan.io/address/0x896df375…feb1ab

Malicious transaction example:

https://arbiscan.io/tx/0x0a637e32…ba4c4a

Recovering transaction example:

https://arbiscan.io/tx/0x0281ff6e…806bd1

Attacker's on-chain message:

https://arbiscan.io/tx/0x38ae6073…13ab9c

Recovering message from the TenderFi:

https://arbiscan.io/tx/0xdeb31360…6e0b72

Address holding the Bug Bounty:

https://arbiscan.io/address/0xd724a36b…203769

This is classified as a Oracle Manipulation & Price Manipulation . Compare similar hacks →

Incident Report

Protocol / Project TenderFi

Date of Incident March 07, 2023

Attack Technique Oracle Issue

Classification Borrowing and Lending

Primary Source View Post-Mortem #1 View Post-Mortem #2 View Post-Mortem #3

Protocol Information

Protocol Type Exploit/Oracle Issue

Affected Token TND

Official Website www.tender.fi/

Protocol Twitter/X @tender_fi

Team Public / Doxxed

Source Code Verified On-Chain

Market Context at Time of Hack

Protocol Links

What the Attacker Needed to Succeed

Understanding the prerequisites for this type of attack helps auditors identify protocols that are most at risk and helps developers build better defenses.

Technical Knowledge Deep understanding of oracle issue and Solidity and EVM internals

Capital Required Seed capital to cover gas and initial position setup

On-Chain Access Ability to interact with smart contracts and deploy a custom exploit contract

Protocol Analysis Identification of the exploitable vulnerability in TenderFi's contract logic - root cause: borrowing and lending

Execution Speed Precise transaction ordering and timing to exploit the vulnerability within a single atomic block

Obfuscation Plan A strategy to launder and move stolen funds - typically through mixers, cross-chain bridges, or decentralized DEX swaps to resist tracing

What Auditors Should Check

Could this have been caught in audit? Yes — skilled auditors routinely flag Oracle Issue vulnerabilities in code review

Audited by PeckShield Inc., Armors Labs — still lost $1.6M. Prior audits don't guarantee safety, especially after post-audit code changes.

If you're auditing a protocol with similar architecture to TenderFi, these are the critical security checks that could have prevented this incident (March 2023).

Verify all logic paths related to Oracle Issue are guarded by proper access controls and input validation - see the Oracle Manipulation & Price Manipulation attack class for patterns
Audit oracle price feeds for manipulation risks - ensure time-weighted average prices (TWAPs) or multi-source aggregators are used, not spot prices
Review privileged functions (owner, admin, governance) for potential abuse vectors - centralization risks should be documented and bounded with timelocks or multi-sigs

Master these auditing techniques with hands-on labs and real exploit scenarios in the Smart Contract Hacking course.

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Funds Recovery

93.9%

Recovered

$1.5M

Net Loss

96589

Security Audit History

PeckShield Inc. 2023-02-14 Report
Armors Labs 2022-09-30 Report

Bug Bounty Immunefi Details

Related Attack Classes

The technique used in this hack maps to these vulnerability classes in our security curriculum:

See all Oracle Manipulation & Price Manipulation examples →

Oracle Manipulation & Price Manipulation

Sources & References

01
Source 1 https://twitter.com/tender_fi/status/1633170112718188549
02
Source 2 https://twitter.com/lookonchain/status/1633063188735614976
03
Source 3 https://cointelegraph.com/news/defi-lender-tender-fi-suffers-exp…

Threat Assessment

Severity Level

MEDIUM

Attack Vector Oracle Issue
Root Cause Borrowing and Lending
Year 2023

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