CVE-2026-34209
mppx: Tempo has a session close voucher bypass vulnerability due to settled amount equality
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.
Attack profile
How easy it is to exploit
- Attack vector
- Network
- Complexity
- Low
- Privileges needed
- None
- User interaction
- None
What an attacker can affect
- Confidentiality
- None
- Integrity
- High
- Availability
- None
Exploit likelihood
What each source reports
CVE List Score used
mppx: Tempo has a session close voucher bypass vulnerability due to settled amount equality
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.
- Record
CVE-2026-34209- CVSS 3.1
- 7.5 High
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:N - Weakness
- CWE-294
- Updated
- 2026-11-02
EUVDEUVD-2026-17455
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.
- Record
EUVD-2026-17455- CVSS 3.1
- 7.5 High
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:N - Updated
- 2026-11-02
GitHub AdvisoriesGHSA-mv9j-8jvg-j8mr
mppx: Tempo has a session close voucher bypass vulnerability due to settled amount equality
Impact
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.
Patches
Fixed in 0.4.11.
Workarounds
There are no workarounds available for this vulnerability.
- Record
GHSA-mv9j-8jvg-j8mr- CVSS 3.1
- 7.5 High
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:N - Weakness
- CWE-294
- Updated
- 2026-11-02
NVD
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.
- Record
CVE-2026-34209- CVSS 3.1
- 7.5 High
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:N - Weakness
- CWE-294
- Updated
- 2026-11-02
OSV
mppx: Tempo has a session close voucher bypass vulnerability due to settled amount equality
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.
- Record
CVE-2026-34209- CVSS 3.1
- 7.5 High
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:N - Weakness
- CWE-294
- Updated
- 2026-11-02
OSVGHSA-mv9j-8jvg-j8mr
mppx: Tempo has a session close voucher bypass vulnerability due to settled amount equality
Impact
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.
Patches
Fixed in 0.4.11.
Workarounds
There are no workarounds available for this vulnerability.
- Record
GHSA-mv9j-8jvg-j8mr- CVSS 3.1
- 7.5 High
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:N - Weakness
- CWE-294
- Updated
- 2026-11-02
Affected products
Affected packages
| Package | Affected | Fixed |
|---|---|---|
mppxnpm |
before 0.4.11 | 0.4.11 |
History
| Recorded | Changed | Sources |
|---|---|---|
| first indexed | CVE List, EUVD, GitHub Advisories, NVD, OSV |
Dates are when Every CVE recorded each change. Upstream dates may differ.
In short
CVE-2026-34209 is a high vulnerability (CVSS 7.5) in Wevm Mppx, published March 29, 2026. No source lists public exploit code. EPSS puts the chance of exploitation in the next 30 days at 0.37%, the 31st percentile. Fixed in mppx 0.4.11.
References
github.com/wevm/mppx/security/advisories/GHSA-mv9j-8jvg-j8mr
nvd.nist.gov/vuln/detail/CVE-2026-34209