GHSA-QPXH-FF8M-C62V
Vulnerability from github – Published: 2026-09-25 21:45 – Updated: 2026-09-25 21:45Details
When the server acts as the fee_payer, mpp Elixir 0.4.0 copies the client-supplied EIP-2930 access list verbatim into the cosigned fee-payer transaction. In cosign_fee_payer, the server re-signs the raw base_fields (index 5 of the 0x76 AASigned envelope) without inspecting the access list field, which is part of the signed payload.
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 amount 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 137 entries and 100 Gwei max_fee_per_gas, this inflates the fee-payer cost from the normal ~51,287 gas to ~380,087 gas — a 7.4× multiplier — while staying within Bandit's default 10,000-byte per-header-field limit (verified empirically).
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 mpp_elixir_PoC.zip
cd mpp_elixir
docker build -t mpp-elixir-access-list .
docker run --rm mpp-elixir-access-list
There are more details in mpp_elixir/README.md
Impact
A malicious client can force the server to pay ~7.4x the normal transaction fee. This dramatically increases operational costs and completely destroys the profit margin on low-cost items.
{
"affected": [
{
"package": {
"ecosystem": "Hex",
"name": "mpp"
},
"ranges": [
{
"events": [
{
"introduced": "0.2.0"
},
{
"fixed": "0.6.0"
}
],
"type": "ECOSYSTEM"
}
]
}
],
"aliases": [],
"database_specific": {
"cwe_ids": [
"CWE-20"
],
"github_reviewed": true,
"github_reviewed_at": "2026-09-25T21:45:16Z",
"nvd_published_at": null,
"severity": "MODERATE"
},
"details": "### Details\nWhen the server acts as the fee_payer, `mpp` Elixir 0.4.0 copies the client-supplied EIP-2930 access list verbatim into the cosigned fee-payer transaction. In `cosign_fee_payer`, the server re-signs the raw `base_fields` (index 5 of the 0x76 AASigned envelope) without inspecting the access list field, which is part of the signed payload.\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 amount 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 137 entries and 100 Gwei `max_fee_per_gas`, this inflates the fee-payer cost from the normal ~51,287 gas to ~380,087 gas \u2014 a **7.4\u00d7 multiplier** \u2014 while staying within Bandit\u0027s default 10,000-byte per-header-field limit (verified empirically).\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 mpp_elixir_PoC.zip\ncd mpp_elixir\ndocker build -t mpp-elixir-access-list .\ndocker run --rm mpp-elixir-access-list\n``` \nThere are more details in `mpp_elixir/README.md`\n\n### Impact\nA malicious client can force the server to pay ~**7.4x** the normal transaction fee. This dramatically increases operational costs and completely destroys the profit margin on low-cost items.",
"id": "GHSA-qpxh-ff8m-c62v",
"modified": "2026-09-25T21:45:16Z",
"published": "2026-09-25T21:45:16Z",
"references": [
{
"type": "WEB",
"url": "https://github.com/ZenHive/mpp/security/advisories/GHSA-qpxh-ff8m-c62v"
},
{
"type": "WEB",
"url": "https://github.com/ZenHive/mpp/commit/5d6338e2334084c5f2a78cfcca474830733ed7e8"
},
{
"type": "PACKAGE",
"url": "https://github.com/ZenHive/mpp"
},
{
"type": "WEB",
"url": "https://github.com/ZenHive/mpp/releases/tag/v0.6.0"
}
],
"schema_version": "1.4.0",
"severity": [
{
"score": "CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:L/VA:N/SC:N/SI:N/SA:N",
"type": "CVSS_V4"
}
],
"summary": "mpp vulnerable to Gas Draining with access list"
}
Drag nodes to arrange them. Double-click a related vulnerability to open it, or a source to visit its link. The Physics button on the left tunes the layout and the simulation; the legend at the bottom left hides or shows nodes by kind and by sighting type.
Sightings
| Author | Source | Type | Date | Other |
|---|
Nomenclature
- Seen: The vulnerability was mentioned, discussed, or observed by the user.
- Confirmed: The vulnerability has been validated from an analyst's perspective.
- Published Proof of Concept: A public proof of concept is available for this vulnerability.
- Exploited: The vulnerability was observed as exploited by the user who reported the sighting.
- 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.
Vulnerability timeline
Sightings and recorded dates, grouped by day · UTC
How durations are calculated
Following the VTEM framework (Black Hat USA 2015), time to patch starts when the vendor or a coordinator was informed, total time to patch at discovery, and disclosure to patch at public disclosure; vendor response time runs from the report to its acknowledgement. Time to exploit and time unpatched start at the earliest discovery or report, falling back to public disclosure. Unpatched time ends at the first recorded patch, or the calculation time when no patch is recorded. Exploitation to patch shows the interval between those two events; a published proof of concept is a public exploit, not exploitation.
Each result shows its source dates. A negative interval means the end event came first; when date-only inputs leave the order open, the result says so. Date-only inputs are approximate. The earliest evidence wins: KEV report dates and sightings are labelled as such. Records describing another vulnerability are listed but never calculated from, and a PoC alone does not establish exploitation. Missing patch evidence does not prove that no patch exists. Filters below change the event list only.
Loading timeline…
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.
Browse all ATT&CK techniques and the vulnerabilities related to each.
Related by attack behaviour
Vulnerabilities whose description is nearest to this one in the vector space of the CIRCL/vulnerability-attack-technique-biencoder model. This is a similarity search over the bi-encoder space (plain cosine), not a classification, and it has no measured accuracy.