CVE-2026-34209 json
mppx: Tempo has a session close voucher bypass vulnerability due to settled amount equality
published 2026-03-29 7 mo ago modified 2026-07-24 3 mo ago also GHSA-mv9j-8jvg-j8mr , EUVD-2026-17455
- cvss
- 7.5
- version 3.1, CNA
- cisa kev
- Not listed
- not in CISA's catalog
- epss
- 0.4%
- EPSS 0.4% chance of exploitation in 30 days, percentile 31%
- public exploits
- 0
- none known
Summary
mppx is a TypeScript interface for machine payments protocol. Prior to version 0.4.11, the tempo/session cooperative close handler validated the close voucher amount using "<" instead of "<=" against the on-chain settled amount. An attacker could submit a close voucher exactly equal to the settled amount, which would be accepted without committing any new funds, effectively closing or griefing the channel for free. This issue has been patched in version 0.4.11.
Patch / fix
- npm mppx 0.4.11
- wevm mppx 0.4.11
CISA SSVC
- Exploitation
- none
- Automatable
- yes
- Technical impact
- partial
- Assessed
- 7 mo ago
Exploit prediction
0.37% chance of exploitation in the next 30 days, higher than 31% of all scored CVEs (FIRST EPSS, 2026-11-08).
CVSS scores
| assigned by | version | score | vector |
|---|---|---|---|
| CNA | 3.1 | 7.5 | CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:N |
| GitHub | 3.1 | 7.5 | CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:N |
Affected packages
| ecosystem | package | affected | fixed in |
|---|---|---|---|
| npm | mppx | <0.4.11 |
0.4.11 |
Affected products
- wevm mppx
Classification
- Weakness
-
- CWE-294 Authentication Bypass by Capture-replay
References
-
github.com
/wevm/mppx/commit/94088246ee18f21b5d6be40d9e7a464f5a280bfb
web, patch
-
github.com
/wevm/mppx/security/advisories/GHSA-mv9j-8jvg-j8mr
web, patch, vendor-advisory
-
github.com
/wevm/mppx/releases/tag/mppx@0.4.11
web, release-notes
-
nvd.nist.gov
/vuln/detail/CVE-2026-34209
advisory
-
github.com
/wevm/mppx
package
Sources
- CVE List CVE-2026-34209
- GitHub Advisory GHSA-mv9j-8jvg-j8mr
- NVD CVE-2026-34209
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