Megapot — Unoptimized subset matches counting exceeds Base tx gas limit

Source & credit. Reproduction of a public audit finding curated by AuditVault — the original finding: 64141-h-02-unoptimized-subset-matches-counting-implementation-will. Standalone Foundry PoC and full write-up: 64141-h-02-unoptimized-subset-matches-counting-implementation-will_exp in the evm-hack-registry mirror.

Reproduction: self-contained Foundry PoC (forge-std only) — no fork. Full trace: output.txt.

AuditVault taxonomy: lang/solidity · platform/code4rena · severity/high · sector/gaming · genome: gas-limit · permanent

Key info#


Impact	HIGH — entropy callback exceeds Base 25M tx gas → drawing never settles
Protocol	Megapot
Bug class	Uncached `generateSubsets` inside `bonusballMax × normalTiers` nested loops
Finding	Code4rena 2025-11-megapot H-02 · #64141
Report	https://code4rena.com/reports/2025-11-megapot
Source	AuditVault
Status	Audit finding — sample+extrapolate gas PoC
Compiler	`^0.8.24` (PoC)

TL;DR#

_countSubsetMatches regenerates subsets for every bonusball. At bonusballMax=129 the settlement callback measures ~25.8M gas and exceeds Base's 25M per-tx limit, so Pyth cannot settle the drawing.

HARM: extrapolated settlement gas at real bonusballMax exceeds Base tx gas limit → permanent drawing DoS.

Root cause#

Uncached combinatorial subset generation inside nested settlement loops.

Preconditions#

Large pool → high bonusballMax (e.g. 129 at 16M USDC cap).

Attack walkthrough#

Sample gas at small bonusballMax, extrapolate linearly to 129, require > 25_000_000.

Diagrams#

flowchart TD A["scaledEntropyCallback"] --> B["_countSubsetMatches"] B --> C["for i in 1..bonusballMax"] C --> D["for k in 1..normalTiers"] D --> E["generateSubsets uncached"] E --> F{"gas > 25M Base limit?"} F -->|Yes| G["callback fails - drawing stuck"]

Impact#

Drawings at high bonusballMax cannot be settled; jackpot liveness fails.

Sources#

AuditVault finding
Report: https://code4rena.com/reports/2025-11-megapot
Reduced source provenance: github.com/code-423n4/2025-11-megapot@f0a7297 TicketComboTracker.sol

Sources & further analysis#

Reproductions & code

Standalone PoC + full trace: 64141-h-02-unoptimized-subset-matches-counting-implementation-will_exp (evm-hack-registry mirror).
AuditVault finding: 64141-h-02-unoptimized-subset-matches-counting-implementation-will.

Alerts & third-party analyses

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