# mppx multiple payment bypass and griefing vulnerabilities

Source: https://junglewise.ai/threats/mppx-multiple-payment-bypass-and-griefing-vulnerabilities-0a27d3d4  
Publisher: Junglewise Threat Intelligence, https://junglewise.ai/threats  
Published: 2026-03-29. Updated: 2026-09-25  
License: CC BY 4.0 with a link back

Severity: medium · CVSS 4 · Published 2026-03-29

mppx is a TypeScript library implementing the Machine Payments Protocol for handling cryptocurrency payment flows and sessions. The library contains multiple critical vulnerabilities in its payment and session handling logic that allow attackers to bypass payment requirements, replay transactions, and manipulate fee payment arrangements—enabling free transactions and disruption of payment channels without authentication requirements.

Technologies: [Wevm Mppx](https://junglewise.ai/threats/technologies/mppx). Vendors: [Wevm](https://junglewise.ai/threats/vendors/wevm).

## Quick answers

**Is This vulnerability exploited in the wild?** No. Junglewise Threat Intelligence has no report of This vulnerability being exploited in the wild.

**How severe is This vulnerability?** Medium severity, with a CVSS score of 4, published 29 March 2026.

**Which products and versions are affected?** Wevm Mppx <0.4.8.

**Is there a fix for This vulnerability?** A patch was published on 2026-03-26: Fixed in version 0.4.8 Junglewise finds every place you run it, drafts the upgrade and applies it once you approve.

**How is This vulnerability attacked?** It is attacked over the network, in a software library.

**Am I affected?** Check whether you run Wevm Mppx at an affected version. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.

## Technical details

Multiple vulnerabilities were discovered in the tempo/charge and tempo/session components, including: transaction hash replay across push/pull modes and concurrent requests, missing transfer log verification enabling free requests in pull-mode, scope confusion allowing credential reuse across routes, missing sender signatures allowing fee payer manipulation, voucher signature verification bypass, weak channel ID binding enabling voucher reuse, channel reopen without on-chain state verification, and force-close detection bypass. All vulnerabilities require no authentication and are exploitable over the network via API calls to the affected payment and session endpoints. An unauthenticated attacker can perform unauthorized transactions, manipulate fee responsibility, and grief payment channels. The vulnerabilities were fixed in version 0.4.8.

## Affected products

- wevm mppx <0.4.8

## Timeline

- 2026-03-26: disclosed
- 2026-03-26: patched: Fixed in version 0.4.8

## References

- [https://github.com/wevm/mppx/security/advisories/GHSA-8x4m-qw58-3pcx](https://github.com/wevm/mppx/security/advisories/GHSA-8x4m-qw58-3pcx)
- [https://github.com/wevm/mppx](https://github.com/wevm/mppx)

## Related threats

- [wevm mppx credential replay in stripe/charge payment method](https://junglewise.ai/threats/cve-2026-34210-wevm-mppx-credential-replay-in-stripe-charge-payment-method)
- [wevm mppx improper validation in tempo session close handler](https://junglewise.ai/threats/cve-2026-34209-wevm-mppx-improper-validation-in-tempo-session-close-handler)