# GHSA-8x4m-qw58-3pcx: mppx has multiple payment bypass and griefing vulnerabilities

> Attackers can bypass payment verification and manipulate session channels in the mppx library, leading to financial loss and service disruption.

- **Severity:** Not scored
- **Exploited in the wild:** Not known
- **Login needed:** Any signed-in user
- **Attackable:** Over the internet
- **Victim action needed:** Not needed
- **Fix available:** Yes
- **Published:** 29 Mar 2026

## What is GHSA-8x4m-qw58-3pcx?

GHSA-8x4m-qw58-3pcx is a vulnerability in mppx, published on 29 Mar 2026. Any signed-in user can exploit it over the network, with no action from the victim.

### Official description

### Impact

Multiple vulnerabilities were discovered in `tempo/charge` and `tempo/session` which allowed for undesirable behaviors, including:
- Replaying `tempo/charge` transaction hashes across push/pull modes, across charge/session endpoints, and via concurrent requests
- Performing free `tempo/charge` requests due to missing transfer log verification in pull-mode
- Replaying `tempo/charge` credentials across routes via cross-route scope confusion (`memo`/`splits` not included in scope binding)
- Manipulating the fee payer of a `tempo/charge` handler into paying for requests (missing sender signature before co-signing)
- Bypassing `tempo/session` voucher signature verification
- Piggybacking off existing `tempo/session` channels via settle voucher reuse and weak channel ID binding
- Performing free `tempo/session` requests by exploiting channel reopen without on-chain settled state
- Accepting deductions on finalized `tempo/session` channels
- Bypassing payment on free routes via method-mismatch fallback
- Griefing `tempo/session` channels via force-close detection bypass (`closeRequestedAt` not persisted)

### Patches

Fixed in 0.4.8.

### Workarounds

There are no workarounds available for these vulnerabilities.

## Which versions are affected by GHSA-8x4m-qw58-3pcx?

2 open source packages ship an affected version, including mppx.


| Package | Ecosystem | Affected | Fixed in |
| --- | --- | --- | --- |
| `mppx` | npm | All versions | 0.4.8 |
| `mppx` | npm | All versions | 0.4.8 |

## How do I fix GHSA-8x4m-qw58-3pcx?

Upgrade mppx to 0.4.8 or later.

## Is GHSA-8x4m-qw58-3pcx being exploited?

There is no known exploitation of GHSA-8x4m-qw58-3pcx in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for GHSA-8x4m-qw58-3pcx and fix it if it is affected.

What it is: GHSA-8x4m-qw58-3pcx is a vulnerability in mppx, published on 29 Mar 2026. Any signed-in user can exploit it over the network, with no action from the victim.
Exploitation: There is no known exploitation of GHSA-8x4m-qw58-3pcx in the wild and no public exploit code.

Affected packages and fixed versions:
- mppx (npm): affected all versions; fixed in 0.4.8
- mppx (npm): affected all versions; fixed in 0.4.8

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/GHSA-8x4m-qw58-3pcx/ (Markdown: https://insights.sbomify.com/GHSA-8x4m-qw58-3pcx/index.md)
```

## Sources

- OSV: https://osv.dev/vulnerability/GHSA-8x4m-qw58-3pcx

---
From sbomify Insights: https://insights.sbomify.com/GHSA-8x4m-qw58-3pcx/
Summaries are generated and may contain mistakes; the official description above is the record.