Vulnerability-Lookup

CVE-2026-63628 (GCVE-0-2026-63628)

Vulnerability from cvelistv5 – Published: 2026-09-22 19:09 – Updated: 2026-09-24 14:17

Title

mppx: Gas Draining with access list

Summary

mppx is a TypeScript interface for machine payments protocol. Prior to 0.8.2, the fee-payer cosigning path in src/tempo/internal/fee-payer.ts copied a client-supplied access_list from a 0x78 FeePayerEnvelope without validating its length or contents. Because EIP-2930 access-list entries consume intrinsic gas even when the listed addresses are never used, a client could add fabricated address-only entries and cause the server fee_payer wallet to pay unnecessary transaction fees. The demonstrated 180-entry list remained within the 500,000 gas policy cap, 16 KB header limit, and RPC simulation budget while increasing the fee by approximately 9.4 times. This issue is fixed in version 0.8.2.

Severity

6.9 (Medium)


                        
                          CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:L/SC:N/SI:N/SA:N

SSVC

Exploitation: poc Automatable: yes Technical Impact: partial

CISA Coordinator · CISA-ADP (v2.0.3)

Decision recorded 2026-09-24 14:17 UTC

CWE

CWE-20 - Improper Input Validation

Assigner

GitHub_M mitre root Scorecard

References

4 references

URL	Tags
https://github.com/wevm/mppx/security/advisories/…	x_refsource_CONFIRM
https://github.com/wevm/mppx/pull/602	x_refsource_MISC
https://github.com/wevm/mppx/commit/24ddcca719ae2…	x_refsource_MISC
https://github.com/wevm/mppx/releases/tag/mppx@0.8.2	x_refsource_MISC

Impacted products

1 product

Vendor	Product	Version	CPE status
wevm	mppx	Affected: < 0.8.2	guessed

Show details on NVD website

JSON

To clipboard

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FKIE_CVE-2026-63628

Vulnerability from fkie_nvd - Published: 2026-09-22 20:17 - Updated: 2026-09-24 15:17

Severity

6.9 (Medium) - CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:L/SC:N/SI:N/SA:N

Summary

References

	URL	Tags
	security-advisories@github.com	https://github.com/wevm/mppx/commit/24ddcca719ae282977d8747309ed1275ea282b25
	security-advisories@github.com	https://github.com/wevm/mppx/pull/602
	security-advisories@github.com	https://github.com/wevm/mppx/releases/tag/mppx@0.8.2
	security-advisories@github.com	https://github.com/wevm/mppx/security/advisories/GHSA-vc9j-9wph-qghj
	134c704f-9b21-4f2e-91b3-4a467353bcc0	https://github.com/wevm/mppx/security/advisories/GHSA-vc9j-9wph-qghj

Impacted products

	Vendor	Product	Version

JSON

To clipboard

{
  "affected": [
    {
      "affectedData": [
        {
          "product": "mppx",
          "vendor": "wevm",
          "versions": [
            {
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    }
  ],
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    }
  ],
  "sourceIdentifier": "security-advisories@github.com",
  "vulnStatus": "Awaiting Analysis",
  "weaknesses": [
    {
      "description": [
        {
          "lang": "en",
          "value": "CWE-20"
        }
      ],
      "source": "security-advisories@github.com",
      "type": "Secondary"
    }
  ]
}

GHSA-VC9J-9WPH-QGHJ

Vulnerability from github – Published: 2026-09-22 20:34 – Updated: 2026-09-22 20:34

Summary

mppx: Gas Draining with access list

Details

When the server acts as the fee_payer, 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 access_list 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 access_list 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 max_fee_per_gas, 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 gas, the Node.js 16 KB header limit, and the Moderato RPC's eth_call simulation budget (verified empirically at 180 entries).

PoC

The PoC is provided below. It is configured to reproduce the attack on Tempo Moderate testnet within a Docker environment. Download the PoC and run:

unzip mppx_typescript_PoC.zip
cd mppx_typescript
docker build -t mppx-typescript-access-list .
docker run --rm mppx-typescript-access-list

There are more details in mppx_typescript/README.md

Impact

A malicious client can force the server to pay ~9.4x the normal transaction fee. This dramatically increases operational costs and completely destroys the profit margin on low-cost items.

Show details on source website

JSON

To clipboard

{
  "affected": [
    {
      "package": {
        "ecosystem": "npm",
        "name": "mppx"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "0"
            },
            {
              "fixed": "0.8.2"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ]
    }
  ],
  "aliases": [
    "CVE-2026-63628"
  ],
  "database_specific": {
    "cwe_ids": [
      "CWE-20"
    ],
    "github_reviewed": true,
    "github_reviewed_at": "2026-09-22T20:34:19Z",
    "nvd_published_at": null,
    "severity": "MODERATE"
  },
  "details": "### Details\nWhen the server acts as the fee_payer, `mppx` 0.6.27 copies the client-supplied EIP-2930 access list verbatim into the cosigned fee-payer transaction. The TypeScript SDK\u0027s fee-payer cosigning path accepts any `access_list` the client includes in the 0x78 `FeePayerEnvelope` without inspecting its length or contents.\n\nAccess list gas is charged **intrinsically** \u2014 before any opcode executes \u2014 regardless of whether the listed addresses are ever touched.\n\nAn attacker submits a valid `transferWithMemo` alongside fabricated address-only access list entries. The server validates calldata and gas parameters but never inspects `access_list` length. It cosigns and broadcasts a transaction that costs the fee-payer wallet `N \u00d7 2,400` extra gas per request with no corresponding work performed on-chain.\n\nAt the default of 180 entries and 100 Gwei `max_fee_per_gas`, this inflates the fee-payer cost from the normal ~51,287 gas to ~483,287 gas \u2014 a **9.4\u00d7 multiplier** \u2014 while staying within the `FeePayerPolicy` cap of 500K gas, the Node.js 16 KB header limit, and the Moderato RPC\u0027s `eth_call` simulation budget (verified empirically at 180 entries).\n\n### PoC\nThe PoC is provided below. It is configured to reproduce the attack on Tempo Moderate testnet within a Docker environment. Download the PoC and run:\n```bash\nunzip mppx_typescript_PoC.zip\ncd mppx_typescript\ndocker build -t mppx-typescript-access-list .\ndocker run --rm mppx-typescript-access-list\n``` \nThere are more details in `mppx_typescript/README.md`\n\n### Impact\nA malicious client can force the server to pay ~**9.4x** the normal transaction fee. This dramatically increases operational costs and completely destroys the profit margin on low-cost items.",
  "id": "GHSA-vc9j-9wph-qghj",
  "modified": "2026-09-22T20:34:19Z",
  "published": "2026-09-22T20:34:19Z",
  "references": [
    {
      "type": "WEB",
      "url": "https://github.com/wevm/mppx/security/advisories/GHSA-vc9j-9wph-qghj"
    },
    {
      "type": "WEB",
      "url": "https://github.com/wevm/mppx/pull/602"
    },
    {
      "type": "WEB",
      "url": "https://github.com/wevm/mppx/commit/24ddcca719ae282977d8747309ed1275ea282b25"
    },
    {
      "type": "PACKAGE",
      "url": "https://github.com/wevm/mppx"
    },
    {
      "type": "WEB",
      "url": "https://github.com/wevm/mppx/releases/tag/mppx@0.8.2"
    }
  ],
  "schema_version": "1.4.0",
  "severity": [],
  "summary": "mppx: Gas Draining with access list"
}

Sightings

Author	Source	Type	Date	Other

Nomenclature

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Confirmed: The vulnerability has been validated from an analyst's perspective.
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Patched: The vulnerability was observed as successfully patched by the user who reported the sighting.
Not exploited: The vulnerability was not observed as exploited by the user who reported the sighting.
Not confirmed: The user expressed doubt about the validity of the vulnerability.
Not patched: The vulnerability was not observed as successfully patched by the user who reported the sighting.

The MITRE ATT&CK techniques below are AI-generated suggestions, inferred from the description of the vulnerability by the CIRCL/vulnerability-attack-technique-classification-roberta-base model, served locally by ML-Gateway. They have not been verified by an analyst and are provided for guidance only.
The approach is described in our paper Mapping CVEs to MITRE ATT&CK Techniques: A Curated Gold-Set Classifier and the Limits of LLM-Assisted Label Expansion.
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Action not permitted

CVE-2026-63628 (GCVE-0-2026-63628)

FKIE_CVE-2026-63628

GHSA-VC9J-9WPH-QGHJ

Details

PoC

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