# CVE-2026-82750: Denial of service in mpp

> An unauthenticated attacker can inflate gas costs for fee-payer sponsorship and force sponsors to pay for account delegations by exploiting unbounded authorization lists.

- **Severity:** High 8.3 (`CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:N/VI:H/VA:L/SC:N/SI:N/SA:N`)
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Over the internet
- **Victim action needed:** Not needed
- **Fix available:** Yes
- **Published:** 6 Sep 2026
- **Updated:** 8 Sep 2026
- **Also known as:** EEF-CVE-2026-82750, GHSA-5qrp-r24c-w6jr, GHSA-q4f3-jf9f-788f

## What is CVE-2026-82750?

CVE-2026-82750 is a high-severity denial of service vulnerability in ZenHive mpp, published on 6 Sep 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.

### Official description

Improper Validation of Specified Quantity in Input in ZenHive mpp allows an unauthenticated remote client to inflate the fee-payer's gas cost per sponsored payment by a large multiplier and to have the sponsor pay for EIP-7702 account delegations of the client's choosing.

When the server sponsors Tempo payments, MPP.Methods.Tempo.FeePayerPolicy.measure/3 in lib/mpp/methods/tempo/fee_payer_policy.ex bounds the gas fields, the fee budget, the validity window and the access list of the client-signed 0x76 envelope, but never reads its aa_authorization_list field. Every signed delegation in that list is charged as intrinsic gas before the payment call runs, so a client attaching delegations from throwaway authority keys makes the sponsor pay for them within the default gas_limit ceiling. At the reporter's default of seven entries the sponsored cost rises from about 46,575 gas to about 1,884,087 gas. Because each entry is applied as a persistent set-code delegation, a client can also upgrade its own accounts to delegated code at the sponsor's expense.

This issue affects mpp: from 0.2.0 before 0.16.1.

Weakness: CWE-1284 (Improper Validation of Specified Quantity in Input)

## Which versions are affected by CVE-2026-82750?

1 open source package ship an affected version, including mpp.


| Package | Ecosystem | Affected | Fixed in |
| --- | --- | --- | --- |
| `mpp` | Hex | From 0.2.0 | 0.16.1 |

## How do I fix CVE-2026-82750?

Upgrade mpp to 0.16.1 or later.

## Is CVE-2026-82750 being exploited?

There is no known exploitation of CVE-2026-82750 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-82750 and fix it if it is affected.

What it is: CVE-2026-82750 is a high-severity denial of service vulnerability in ZenHive mpp, published on 6 Sep 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.
Exploitation: There is no known exploitation of CVE-2026-82750 in the wild and no public exploit code.

Affected packages and fixed versions:
- mpp (Hex): affected from 0.2.0; fixed in 0.16.1

Task:
1. Search the dependency manifests and lockfiles (for example package.json, package-lock.json, requirements.txt, poetry.lock, uv.lock, pom.xml, build.gradle, go.mod, Cargo.lock, Gemfile.lock) and any Dockerfiles for the affected packages, including transitive dependencies.
2. If an affected version is in use, upgrade it to the fixed version for its release line with the project's package manager, so the lockfile is regenerated. Prefer the smallest upgrade that fixes it.
3. If there is no fix, or the upgrade would break the build, do not guess: explain the risk and the safest workaround instead.
4. Run the tests and summarise what changed and why.
5. If nothing in the project is affected, say so and change nothing.

Reference: https://insights.sbomify.com/CVE-2026-82750/ (Markdown: https://insights.sbomify.com/CVE-2026-82750/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-82750
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-82750
- OSV: https://osv.dev/vulnerability/CVE-2026-82750

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-82750/
Summaries are generated and may contain mistakes; the official description above is the record.