mppx: Gas Draining with access list

Exploitation

No confirmed exploitation recorded. Patch Next marks exploitation only from CISA KEV.

CVSS

not scored

EPSS

• CVE-2026-63628: 0.49% estimated exploitation activity in the next 30 days; percentile 41.99 (FIRST EPSS, 2026-11-03). This is a model estimate, not proof of exploitation or customer exposure.

As published by the source; long descriptions are shortened.

Details When the server acts as the feepayer, mppx 0.6.27 copies the client-supplied EIP-2930 access list verbatim into the cosigned fee-payer transaction. The TypeScript SDK's fee-payer cosigning path accepts any accesslist the client includes in the 0x78 FeePayerEnvelope without inspecting its length or contents. Access list gas is charged intrinsically — before any opcode executes — regardless of whether the listed addresses are ever touched. An attacker submits a valid transferWithMemo alongside fabricated address-only access list entries. The server validates calldata and gas parameters but never inspects accesslist length. It cosigns and broadcasts a transaction that costs the fee-payer wallet N × 2,400 extra gas per request with no corresponding work performed on-chain. At the default of 180 entries and 100 Gwei maxfeepergas, this inflates the fee-payer cost from the normal ~51,287 gas to ~483,287 gas — a 9.4× multiplier — while staying within the FeePayerPolicy cap of 500K…

Published by the source

22 Sep 2026, 20:34 UTC

Last modified by the source

22 Sep 2026, 21:00 UTC

Source last checked

26 Oct 2026, 13:02 UTC

1. Revision 3 · amended · 26 Oct 2026

   Amended from ghsa record GHSA-vc9j-9wph-qghj

2. Revision 2 · amended · 24 Oct 2026

   Amended from osv record GHSA-vc9j-9wph-qghj

3. Revision 1 · created · 23 Oct 2026

   Published from ghsa record GHSA-vc9j-9wph-qghj

Preview the exact text before you copy it. Commands are read-only suggestions; review them before running anything.

# Patch Next advisory brief: CVE-2026-63628

Advisory: mppx: Gas Draining with access list
IDs: CVE-2026-63628, GHSA-vc9j-9wph-qghj
Record: https://patchnext.com/advisories/cve-2026-63628 (revision 3, source checked 26 Oct 2026, 13:02 UTC)
Inventory: none attached. This brief comes from a public page and does not say whether any deployment is affected.
Severity: Unrated
Exploitation: no confirmed exploitation recorded. Patch Next confirms exploitation only from CISA KEV.
Vendor response: Vendor fix available; fixed versions by package: mppx 0.8.2. A vendor fix does not mean a deployment is fixed.

## Affected components
- npm mppx: affected < 0.8.2; fixed in 0.8.2

## Suggested inspection (read-only)
- `npm ls mppx --all`: lists every installed copy and version, including transitive ones. Run in the project root after `npm ci`.

## Supported action
Upgrade each affected component to a fixed version on its release line. For a transitive dependency, upgrade the parent package or add an override or constraint, then regenerate the lockfile. Redeploy every environment that ran an affected version.

## Required regression checks
- Run the test suite and a production build.
- Exercise the features that depend on mppx.
- Repeat the inspection and confirm that only fixed versions remain installed.

## Rollback considerations
- Keep the previous lockfile and deployment artifact. Rolling back reinstates the vulnerable version, so apply any documented mitigation while you fix forward.

## Unresolved questions
- Which deployments run an affected version?
- Exploitation status can change. Check again before lowering the priority.
- Mark the work resolved only after the fixed version is verified in production.

## Sources
- Verified: https://github.com/advisories/GHSA-vc9j-9wph-qghj (GitHub-reviewed advisory GHSA-vc9j-9wph-qghj lists affected ranges: npm mppx >=0 <0.8.2)
- Verified: https://osv.dev/vulnerability/GHSA-vc9j-9wph-qghj (OSV record GHSA-vc9j-9wph-qghj lists affected ranges: npm mppx >=0 <0.8.2 (fixed))

Commands are suggestions: review each one before running it.