Prepared by:
HALBORN
Last Updated 05/14/2026
Date of Engagement: April 29th, 2026 - May 8th, 2026
100% of all REPORTED Findings have been addressed
All findings
6
Critical
0
High
0
Medium
1
Low
1
Informational
4
Trufin engaged Halborn to conduct a security assessment of their TRUBILL Solana Program beginning on April 29th, 2026, and ending on May 8th, 2026. The security assessment was scoped to the Solana Programs provided in solana-vaults-audit GitHub repository. Commit hashes and further details can be found in the Scope section of this report.
TruBill is a Solana vault that accepts USDC deposits and issues TruBILL share tokens in return. It routes the majority of deposits through an external protocol (Delta Manager) to earn yield on ULTRA, while keeping a configurable USDC reserve for immediate liquidity. Share prices are updated once per epoch based on Delta Manager's published NAV.
Users can exit either instantly drawing from the reserve with a small fee or through a slower path where shares are burned now and USDC is claimed after the operator completes a redemption cycle through Delta Manager. An owner governs risk parameters and an operator handles all external asset movements.
Halborn was provided 7 days for the engagement and assigned one full-time security engineer to review the security of the Solana Programs in scope. The engineer is a blockchain and smart contract security expert with advanced smart contract hacking skills, and deep knowledge of multiple blockchain protocols.
The purpose of the assessment is to:
Identify potential security issues within the Solana Programs.
Ensure that smart contract functionality operates as intended.
In summary, Halborn identified some improvements to reduce the likelihood and impact of risks, which have been addressed by the Trufin team. The main recommendations were:
Track the redeem-request id in a per-user state PDA rather than the global vault_config
Track the sum of unclaimed RedeemRequest.usdc_owed in a dedicated field on UsdcAccounting and require the post-reconcile owed_to_users to remain at or above that sum
Halborn performed a combination of a manual review of the source code and automated security testing to balance efficiency, timeliness, practicality, and accuracy in regard to the scope of the program assessment. While manual testing is recommended to uncover flaws in business logic, processes, and implementation; automated testing techniques help enhance coverage of programs and can quickly identify items that do not follow security best practices.
The following phases and associated tools were used throughout the term of the assessment:
Research into the architecture, purpose, and use of the platform.
Manual program source code review to identify business logic issues.
Mapping out possible attack vectors
Thorough assessment of safety and usage of critical Rust variables and functions in scope that could lead to arithmetic vulnerabilities.
Scanning dependencies for known vulnerabilities (cargo audit).
Local runtime testing (just test)
| EXPLOITABILITY METRIC () | METRIC VALUE | NUMERICAL VALUE |
|---|---|---|
| Attack Origin (AO) | Arbitrary (AO:A) Specific (AO:S) | 1 0.2 |
| Attack Cost (AC) | Low (AC:L) Medium (AC:M) High (AC:H) | 1 0.67 0.33 |
| Attack Complexity (AX) | Low (AX:L) Medium (AX:M) High (AX:H) | 1 0.67 0.33 |
| IMPACT METRIC () | METRIC VALUE | NUMERICAL VALUE |
|---|---|---|
| Confidentiality (C) | None (C:N) Low (C:L) Medium (C:M) High (C:H) Critical (C:C) | 0 0.25 0.5 0.75 1 |
| Integrity (I) | None (I:N) Low (I:L) Medium (I:M) High (I:H) Critical (I:C) | 0 0.25 0.5 0.75 1 |
| Availability (A) | None (A:N) Low (A:L) Medium (A:M) High (A:H) Critical (A:C) | 0 0.25 0.5 0.75 1 |
| Deposit (D) | None (D:N) Low (D:L) Medium (D:M) High (D:H) Critical (D:C) | 0 0.25 0.5 0.75 1 |
| Yield (Y) | None (Y:N) Low (Y:L) Medium (Y:M) High (Y:H) Critical (Y:C) | 0 0.25 0.5 0.75 1 |
| SEVERITY COEFFICIENT () | COEFFICIENT VALUE | NUMERICAL VALUE |
|---|---|---|
| Reversibility () | None (R:N) Partial (R:P) Full (R:F) | 1 0.5 0.25 |
| Scope () | Changed (S:C) Unchanged (S:U) | 1.25 1 |
| Severity | Score Value Range |
|---|---|
| Critical | 9 - 10 |
| High | 7 - 8.9 |
| Medium | 4.5 - 6.9 |
| Low | 2 - 4.4 |
| Informational | 0 - 1.9 |
Critical
0
High
0
Medium
1
Low
1
Informational
4
| Security analysis | Risk level | Remediation Date |
|---|---|---|
| Global Redeem Request Counter Causes Race Condition and DoS | Medium | Solved - 05/13/2026 |
| Reconcile USDC overstatement blocks slow-path redeem claims | Low | Solved - 05/13/2026 |
| Instant redeem fee can be bypassed via small redeem amounts | Informational | Solved - 05/13/2026 |
| Risk of initialization front-running | Informational | Acknowledged - 05/13/2026 |
| Redeemer USDC can be permanently locked by whitelist revocation after request_redeem | Informational | Solved - 05/13/2026 |
| Missing input validation across multiple instructions | Informational | Solved - 05/13/2026 |
//Medium
//Low
//Informational
//Informational
//Informational
//Informational
Halborn strongly recommends conducting a follow-up assessment of the project either within six months or immediately following any material changes to the codebase, whichever comes first. This approach is crucial for maintaining the project’s integrity and addressing potential vulnerabilities introduced by code modifications.
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