Critical Vulnerability Disclosure

On Friday 2026-01-16 we were contacted by an individual from OtterSec (osec.io) who reported a critical vulnerability affecting Triton VM and Neptune Cash. After thoroughly investigating the report, we have confirmed the vulnerability and its impact.

The Vulnerability

The vulnerability is a bug in Triton VM rendering the proof system unsound. Details will be forthcoming. For now it suffices to summarize the situation as follows: an attacker knowledgeable of the vulnerability is capable of forging valid proofs of (or rather: proofs causing the verifier to accept) false claims with very little work. The vulnerability was found despite the scrupulous engineering of the developers and despite the 2024 audit which failed to find any cryptographic vulerabilities.

The Impact

For cryptocurrencies built on top of Triton VM, such as Neptune Cash, it means that an attacker can initiate valid transactions that generate undetectable inflation, exceeding the supply limit and inflation schedule. Attackers may have done this in the past. Or not. There is no way to know.

Fix

The good news is that the fix for Triton VM is rather straightforward and has already been pushed to master on triton-vm and even deployed as version 2.0.0. Corresponding changes to tasm-lib are being made at time of writing. To the best of our knowledge, the proof system with the new patch is sound.

The bad news is that fixing Neptune Cash is rather complicated. Deploying an emergency hard fork and proceeding from there threatens to lock into place any inflationary transactions that may have been initiated in the past. For the founders of Neptune Cash, the single most important feature of any cryptocurrency is its immutable supply evolution. Since we cannot rule out that these inflationary transactions may have occurred, we are compelled to once again reboot the network in order to start with a clean slate in terms of money supply.

We believe that this course of action is in the interest of the vast majority of holders of Neptune Cash. The value of a currency is hurt if unintentional inflation has taken place, or if the total supply is uncertain.

Redemption Process

In order to guarantee continuity of ownership as best as possible a) under the constraint that the money supply limit be fixed and concretely 42'000'000 NPT or less, and b) under the assumption that the vulnerability was not exploited until recently (if at all), we take a snapshot of the UTXO set after block 23400, d02887e40f6a5cfaf12b62b189ab8fc2c4198a057614612b49951521d9139495dae5090000000000. Holders of UTXOs in this snapshot will be able to exercise redemption claims against a claims fund that will be initially populated with all the block subsidies of the first 23400 blocks. If the vulnerability was never exploited, then holders at this point in time can be made whole. If the vulnerability was exploited and the inflation happened before or in this block, then the attacker will be able to redeem funds instead of legitimate holders until the claims fund runs out. The funds of premine recipients are guaranteed and need not be redeemed.

More details on the redemption process will follow. For now make sure to spin up your node and synchronize to the network because doing so will populate you incoming_randomness.dat -- a file you will certainly need to exercise your claims when the redemption process is ready. The claims fund will be custodied by the core developers until a smart contract is ready that can manage disbursements.

Relaunch

The fix to Triton VM is rather straightforward, and no vulnerability in neptune-core is known. Moreover, the smart contract that manages the redemption claims fund need not be ready from day one. So in principle, we could re-launch immediately. However, we decided to use the opportunity provided by a reboot to fix some architectural ugly spots that would otherwise be almost impossible to fix, even with a hard fork. So we are anticipating some network downtime going forwards. For a checklist of tasks and progress monitor before relaunch, check the github issue.

The last few months we have seen tremendous progress in the amount of external contributions to the Neptune Cash ecosystem. This is a development we are excited about, and one that we believe bodes well for this cryptocurrency.

Trading

In coordination with SafeTrade, we have decided to keep trading open. Safetrade reports that withdrawals and deposits remain closed until the network relaunches. Furthermore, we will prioritize, as we did before, SafeTrade's redemption claim, so as to optimize the likelihood that holders on SafeTrade can be made whole.

Thank You

We would like to close this statement with a heartfelt note of gratitude towards OtterSec for finding the vulnerability, their responsible disclosure of it, and the excellent quality of their report. For their effort we decided to award them a bounty of 50'000 NPT.

OtterSec performed this audit spontaneously and without contractual agreement with us, but as a charity service to the community. If you want to share in our appreciation of their labor and professional conduct, please consider sending them some love or an ETH donation to 0x0602996becBC838246f0F6bD84fAD3a7015c401E.