CVE-2026-34209: mppx Tempo Has A Session Close Vulnerability

HIGH
Advisory Identifier: GHSA-mv9j-8jvg-j8mr
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CVSS 7.5
CWE-294
Published
Advisory Summary

CVE-2026-34209 is a HIGH (CVSS 7.5) tempo has a session close vulnerability (CWE-294: Authentication Bypass by Capture-replay) affecting mppx libraries in the npm ecosystem. The issue involves tempo has a session close voucher bypass vulnerability due to settled amount equality. Remediation is available by upgrading affected packages to version 0.4.11.

CVE-2026-34209 at a Glance

CVE Identifier CVE-2026-34209
GHSA Identifier GHSA-mv9j-8jvg-j8mr
Severity HIGH
CVSS v3.1 Base Score 7.5
CWE Classification CWE-294: Authentication Bypass by Capture-replay
Affected Product mppx
Package Ecosystem npm
Published Date
Last Updated

Security Impact

CVSS: 7.5

The security impact metrics below are parsed directly from the CVSS v3.1 vector string (CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:N).

Attack Vector Network (AV:N)
Attack Complexity Low (AC:L)
Privileges Required None (PR:N)
User Interaction None (UI:N)
Scope Unchanged (S:U)
Confidentiality None (C:N)
Integrity High (I:H)
Availability None (A:N)

How to Fix CVE-2026-34209

To remediate this vulnerability, upgrade all affected mppx dependencies to a patched release. Both direct and transitive dependencies should be checked, as frameworks or security libraries may pull in vulnerable versions transitively.

mppx fixed: 0.4.11 
npm install mppx@0.4.11
Verify Direct and Transitive Dependencies

Run the following command in your project directory to verify that all resolved dependencies use the patched release: 

npm ls mppx

How to Check if You Are Affected

To determine whether your Node.js application is affected by CVE-2026-34209, inspect your project dependencies using npm:

npm ls mppx

Analyze the terminal output to locate any version of mppx in your dependency tree. If any resolved version matches the vulnerable ranges listed in the table below (for example, versions earlier than 0.4.11), your application is affected.

Note: The npm ls mppx command inspects dependencies declared in your package.json and lockfile; it does not perform automated runtime dynamic scanning.

Technical Details

Vulnerability Mechanism & Technical Analysis

This vulnerability is classified under CWE-294: Authentication Bypass by Capture-replay, where a capture-replay flaw exists when the design of the product makes it possible for a malicious user to sniff network traffic and bypass authentication by replaying it to the server in question to the same effect as the original message (or with minor changes). In mppx, software state validation or input boundaries are circumvented during processing. Review the official source advisory statement below for specific affected components, classes, and reproduction details.

Source Advisory Statement

### 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.

CVE-2026-34209 Affected mppx Versions

1 component(s)
Fixed Versions:
0.4.11
Product / Package Ecosystem Affected Versions Fixed Version
mppx
npm/mppx
npm
< 0.4.11
0.4.11

References

GitHub Advisory / Wiki ADVISORY
https://github.com/wevm/mppx/security/advisories/GHSA-mv9j-8jvg-j8mr
NVD — CVE-2026-34209 NVD
https://nvd.nist.gov/vuln/detail/CVE-2026-34209
Security Fix Commit FIX COMMIT
https://github.com/wevm/mppx/commit/94088246ee18f21b5d6be40d9e7a464f5a280bfb
mppx Source Repository REPOSITORY
https://github.com/wevm/mppx
mppx Release RELEASE
https://github.com/wevm/mppx/releases/tag/mppx@0.4.11

Frequently Asked Questions

What is CVE-2026-34209?
CVE-2026-34209 is a security vulnerability in mppx involving Tempo has a session close voucher bypass vulnerability due to settled amount equality under CWE-294: Authentication Bypass by Capture-replay.
Which mppx versions are affected?
Affected versions include releases prior to 0.4.11 across affected packages: mppx.
What version fixes CVE-2026-34209?
Upgrading to 0.4.11 (or the latest patched release for your respective branch) resolves the vulnerability.
Is mppx affected?
Yes, mppx is affected in releases prior to 0.4.11. Upgrade your dependency to 0.4.11 or later.
What is the CVSS score of CVE-2026-34209?
CVE-2026-34209 has a CVSS v3.1 base score of 7.5 (HIGH) with vector string CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:N.
What CWE is associated with CVE-2026-34209?
CVE-2026-34209 is classified under CWE-294: Authentication Bypass by Capture-replay (A capture-replay flaw exists when the design of the product makes it possible for a malicious user to sniff network traffic and bypass authentication by replaying it to the server in question to the same effect as the original message (or with minor changes).).
How can I check npm dependencies for CVE-2026-34209?
Run the dependency tree command: 'npm ls mppx'. This command lists direct and transitive dependencies in your build configuration so you can verify if a vulnerable version is resolved.
Machine-readable OSV JSON OSV v1.5 Schema
Normalized schema output
View Raw JSON 
{
  "schema_version" : "1.4.0",
  "id" : "GHSA-mv9j-8jvg-j8mr",
  "modified" : "2026-03-31T18:51:04Z",
  "published" : "2026-03-29T15:10:03Z",
  "aliases" : [ "CVE-2026-34209" ],
  "summary" : "mppx: Tempo has a session close voucher bypass vulnerability due to settled amount equality",
  "details" : "### Impact\n\nThe `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.\n\n### Patches\n\nFixed in 0.4.11.\n\n### Workarounds\n\nThere are no workarounds available for this vulnerability.",
  "severity" : [ {
    "type" : "CVSS_V3",
    "score" : "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:N"
  } ],
  "affected" : [ {
    "package" : {
      "ecosystem" : "npm",
      "name" : "mppx"
    },
    "ranges" : [ {
      "type" : "ECOSYSTEM",
      "events" : [ {
        "introduced" : "0"
      }, {
        "fixed" : "0.4.11"
      } ]
    } ]
  } ],
  "references" : [ {
    "type" : "WEB",
    "url" : "https://github.com/wevm/mppx/security/advisories/GHSA-mv9j-8jvg-j8mr"
  }, {
    "type" : "ADVISORY",
    "url" : "https://nvd.nist.gov/vuln/detail/CVE-2026-34209"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/wevm/mppx/commit/94088246ee18f21b5d6be40d9e7a464f5a280bfb"
  }, {
    "type" : "PACKAGE",
    "url" : "https://github.com/wevm/mppx"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/wevm/mppx/releases/tag/mppx@0.4.11"
  } ],
  "database_specific" : {
    "cwe_ids" : [ "CWE-294" ],
    "severity" : "HIGH",
    "github_reviewed" : true,
    "github_reviewed_at" : "2026-03-29T15:10:03Z",
    "nvd_published_at" : "2026-03-31T15:16:18Z"
  }
}