CVE-2026-34209: mppx: Tempo has a session close voucher bypass vulnerability due to settled amount equality

March 29, 2026 (updated March 31, 2026)

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.

References

github.com/advisories/GHSA-mv9j-8jvg-j8mr
github.com/wevm/mppx
github.com/wevm/mppx/commit/94088246ee18f21b5d6be40d9e7a464f5a280bfb
github.com/wevm/mppx/releases/tag/mppx@0.4.11
github.com/wevm/mppx/security/advisories/GHSA-mv9j-8jvg-j8mr
nvd.nist.gov/vuln/detail/CVE-2026-34209

Code Behaviors & Features

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