STBL redemption: the first iDeposit stores a wrong-asset NFT and locks 1 VAL

Source & credit. Reproduction of a public audit finding curated by AuditVault — the original finding: 66731-missing-assetid-validation-in-stbl-redemption-coreideposit-f. Standalone Foundry PoC and full write-up: 66731-missing-assetid-validation-in-stbl-redemption-coreideposit-f_exp in the evm-hack-registry mirror.

Vulnerability classes: vuln/logic/missing-check · vuln/dos/frozen-funds

Key info#

Field	Value
Loss	1 VAL locked in the redemption pool. The honest 10000 VAL deposit reverts, and redeem reverts
Vulnerable contract	`RedemptionCore.iDeposit`
Attacker EOA	`0x1111111111111111111111111111111111111111`
Attack contract	`Exploit`
Attack tx	`Exploit.run()`
Chain / block / date	Ethereum model · block 0 · 2026-06
Compiler	solc 0.8.27, cancun, via IR
Bug class	First deposit sets `NFTID = id` with no `assetID == AssetID` check

TL;DR#

On an empty pool, iDeposit reads stableValueNet and assigns NFTID = _id. It never checks MetaData.assetID against the pool's AssetID. An asset-2 NFT becomes the pooled position. The next deposit, an asset-1 NFT worth 10000 VAL, hits merge and reverts with STBL_InvalidAsset. redeem compares the pooled asset with AssetID and reverts, so the attacker's 1 VAL stays in the pool. A caller that checks assetID before iDeposit rejects the foreign NFT and redeems a real deposit.

Background#

Cyfrin's June 2026 STBL ESS review, reported by Stalin. STBL_Redemption_Core keeps one pooled YLD NFT. Later deposits merge into it, and merge requires both NFTs to share an assetID. The first deposit skips that merge, which is the only place the asset is checked.

The vulnerable code#

SOLIDITY

if (NFTID == 0) {
    // @> VULN: first deposit stores _id and never checks MetaData.assetID == AssetID
    NFTID = id;
} else {
    NFTID = splitter.merge(NFTID, id);
}

merge is the check the first branch skips:

SOLIDITY

require(metaA.assetID == metaB.assetID, "STBL_InvalidAsset");

Root cause#

iDeposit uses stableValueNet for the share total and ignores assetID when NFTID is still 0. After that write, every honest deposit takes the merge branch and reverts, and redeem refuses to pay a foreign NFT out through the configured asset.

Preconditions#

The pool is constructed for asset 1 and NFTID is 0.
The attacker holds YLD id 2, asset 2, value 1 VAL, and has approved the pool.
The LP holds YLD id 1, asset 1, value 10000 VAL.

Attack walkthrough#

iDeposit(2) pulls the NFT and 1 VAL, then sets NFTID to 2.
The LP calls iDeposit(1). merge sees asset 2 against asset 1 and reverts. The LP still holds the NFT and the 10000 VAL.
redeem loads the pooled asset, finds 2 instead of 1, and reverts.
The pool still holds 1 VAL and NFT 2.
The control requires assetID == AssetID before iDeposit. The foreign NFT reverts, the asset-1 deposit is accepted, and redeem returns the 10000 VAL.

Diagrams#

flowchart TD A["Empty pool configured for asset 1"] --> B["Attacker deposits NFT 2 for asset 2"] B --> C["VULN iDeposit sets NFTID to 2 with no asset check"] C --> D["Honest deposit of the asset-1 NFT hits merge"] D --> E["merge reverts STBL_InvalidAsset and the 10000 VAL stays with the LP"] C --> F["redeem compares pooled asset 2 with AssetID 1 and reverts"] F --> G["1 VAL remains locked in the pool"] B --> H["Control rejects asset 2 before iDeposit"] H --> I["Asset 1 deposits and redeem returns the value"]

Impact#

1 VAL is locked in the redemption contract and redeem cannot release it. Every later deposit of the pool's real asset reverts, including the LP's 10000 VAL NFT, which is not consumed only because the call reverts. The pool has to be replaced. The checked path deposits the real asset and redeems it.

Remediation#

After reading MetaData, require meta.assetID == AssetID before the NFTID == 0 branch. STBL_InvalidAsset is the error merge already uses.

How to reproduce#

BASH

cd 66731-missing-assetid-validation-in-stbl-redemption-coreideposit-f_exp
forge test -vv

test_exploit_wrong_asset_locks_1_ether_and_bricks_pool asserts the pool holds 1 VAL, the LP deposit reverts, and redeem reverts. test_control_asset_check_rejects_wrong_nft_and_redeems asserts the foreign id is rejected and a correct deposit redeems cleanly. Captured output is output.txt.

Sources#

Sources & further analysis#

Reproductions & code

Standalone PoC + full trace: 66731-missing-assetid-validation-in-stbl-redemption-coreideposit-f_exp (evm-hack-registry mirror).
AuditVault finding: 66731-missing-assetid-validation-in-stbl-redemption-coreideposit-f.

Alerts & third-party analyses

Web3Sec X hacked database: search.
Rekt leaderboard: search.
Solodit incident search: search.

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