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• 4 min read

YieldCore-3rd-deal Vault Drained for
$398K Due to Missing Caller Authorization Checks

The YieldCore-3rd-deal USDC vault was reportedly drained for about $398,000 after an attacker exploited a contract path that lacked caller authorization checks. Public reports attribute the incident to a missing permission verification that let the attacker bypass the vault's authorization mechanism and withdraw all funds.

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YieldCore-3rd-deal Vault Drained for $398K Due to Missing Caller Authorization Checks
  • Incident Date: April 29, 2026
  • Target: YieldCore-3rd-deal vault
  • Target Overview: YieldCore-3rd-deal is a USDC-denominated vault listed on TradingStrategy.ai. The vault page identified it as an Ethereum vault with a peak and current TVL of approximately 398,656 USDC before the public incident reports.
  • Total Loss: ~$398,000
  • Attack Vector: Missing Caller Authorization Check / Access Control Bypass

Incident Review & Technical Details​

1. Attack Path​

  1. Vault Selected: The attacker targeted the YieldCore-3rd-deal vault, a USDC-denominated vault on Ethereum. Public vault data showed a TVL of roughly $398.7K, closely matching the reported loss amount.
  2. Authorization Gap Identified: ChainCatcher and PANews reported that the vulnerable contract lacked proper caller permission verification. In practical terms, a sensitive fund-moving path accepted a call without proving that the caller was an authorized vault role, strategy module, owner, or whitelisted executor.
  3. Authorization Mechanism Bypassed: Because the caller check was missing or incomplete, the attacker could invoke the vulnerable path directly instead of going through the intended vault workflow.
  4. Full Vault Withdrawal: The attacker used the bypass to transfer all funds out of the vault. Public reports describe the loss as approximately $398,000, with on-chain transaction records disclosed by monitoring accounts.
  5. Third-Party Vault Boundary: The affected asset should be tracked as the specific YieldCore-3rd-deal vault rather than a confirmed compromise of a broader protocol core. The TradingStrategy.ai vault page listed the protocol as not yet identified/supported, and no detailed project-side post-mortem had been published at the time of writing.

2. Impact Scope​

  • Direct Losses: Approximately $398,000 was withdrawn from the affected vault.
  • Asset Type: The vault was denominated in USDC.
  • Network: Ethereum mainnet, according to the vault's public technical details.
  • Affected Component: The publicly identified affected component was the YieldCore-3rd-deal vault contract.
  • Unaudited Root Cause Detail: Current public reporting confirms the general class of vulnerability, but does not provide a complete function-level post-mortem. The exact vulnerable function, privilege model, and full transaction sequence should be confirmed from on-chain traces before assigning deeper architectural blame.

3. Root Cause Assessment​

The incident fits a classic missing access control pattern:

  • Sensitive Function Exposed: A function capable of moving vault assets was reachable by an unauthorized caller.
  • Role Enforcement Missing or Misplaced: The contract did not sufficiently validate msg.sender, caller role, delegated executor status, or strategy ownership before allowing the fund movement.
  • Vault Balance Concentration: Because the vulnerable path could reach the vault's liquid balance, a single successful call could drain the entire vault instead of causing a bounded partial loss.
  • Insufficient Defense in Depth: Additional controls such as withdrawal caps, timelocks, strategy-only routing, or emergency balance limits could have reduced blast radius even if the primary caller check failed.

This is a reminder that DeFi vault security depends not only on yield strategy correctness, but also on strict authorization around every function that can transfer, withdraw, redeem, rebalance, or delegate assets.

4. Security Takeaways​

  • Every fund-moving function should enforce explicit caller authorization, even if the function is expected to be reached only through an internal workflow.
  • Access control should be tested at the negative-case level: unauthorized EOAs, unrelated contracts, stale strategy modules, and removed operators must all fail.
  • Vaults should enforce circuit breakers such as per-transaction withdrawal limits, rate limits, emergency pauses, and strategy allowlists.
  • Public vault listings should clearly distinguish platform UI aggregation from ownership or operational control of a vault.
  • Monitoring should alert when a single call withdraws an abnormal share of vault TVL or routes funds to a first-seen address.

AUTOSEC.DEV Solution: Building a 360-Degree Defense​

Vault exploits often come from small authorization mistakes in high-impact functions. AUTOSEC.DEV helps DeFi teams and vault managers catch these issues before they become a full-balance drain.

  1. Smart Contract Access Control Audit: We review all privileged and fund-moving paths, including role checks, module permissions, delegated execution, upgrade permissions, and emergency controls.
  2. Vault Strategy Security Review: We test deposit, withdrawal, redemption, rebalance, executor, and fee paths for unauthorized access and accounting edge cases.
  3. Invariant & Negative-Case Testing: We build tests that prove unauthorized callers cannot move assets, change strategy state, or bypass the intended workflow.
  4. Incident Response (IR): AUTOSEC.DEV provides rapid exploit triage, on-chain trace analysis, containment planning, and post-mortem support for vault and strategy incidents.

Service Content​

Reference​

https://x.com/DefimonAlerts/status/2049365873069097237