mppx Security Update Addresses 2 Vulnerabilities
Tech GuruQuick Answer
mppx 0.8.2 fixes two ways a client can inflate fees paid by a server sponsoring Tempo transactions. One adds unused calldata bytes; the other adds unnecessary access-list entries. Both consume gas even when the intended transfer remains valid. Update the fee-payer service, not only its clients.
Confirm Scope And Apply The Supported Fix
What to do now: Identify servers using mppx fee sponsorship, update their deployed dependency to 0.8.2, and review unusual fee-payer spending while the rollout is in progress.
Last verified: 2026-09-23 UTC. Recheck the authoritative advisory and supported distribution channel before changing production.
Scope And Authority
| Product scope | mppx packages and release streams identified in the project advisories |
|---|---|
| Advisory | GHSA-727h-3vm5-qwq6 / GHSA-vc9j-9wph-qghj |
| CVEs | CVE-2026-63627, CVE-2026-63628 |
| Project advisory publication | 2026-07-01 17:23:15-17:23:20 UTC (two project advisories) |
| Recorded source timestamp (historical snapshot) | 2026-09-22 20:34:21 UTC |
| Affected versions | The current CNA records identify versions before 0.8.2 for both CVEs. The GHSA affected fields disagree: the padding advisory says before 0.8.1, and the access-list advisory says after 0.8.1 despite naming 0.8.2 as fixed. Use the confirmed fixed target rather than inferring safety from those fields. |
| Fixed version | mppx 0.8.2 |
| CVSS base score | 6.9 (CVSS v4) |
| CVSS severity | Medium |
| Exploitation status | Not stated by the authority; no exploitation claim is inferred. |
What Changed
CVE-2026-63627 concerns a calldata decoder that accepts trailing bytes, leaving fee sponsorship open to unnecessary intrinsic gas costs. CVE-2026-63628 concerns unvalidated client-supplied EIP-2930 access lists, whose entries cost gas even if unused. The 0.8.2 release notes say non-canonical calldata and client-supplied access lists are rejected before sponsorship.
What To Validate Now
- Inventory. Locate mppx packages and release streams identified in the project advisories deployments, versions, enabled features, exposure paths, owners, and dependent services.
- Establish applicability. Check whether the server acts as the fee payer and accepts client transaction envelopes. The CNA places both issues before 0.8.2; resolve older-version exceptions with the maintainer rather than relying on inconsistent GHSA range fields.
- Remediate. Apply mppx 0.8.2 through the supported vendor or project channel, following the current advisory and change-control requirements.
- Validate. In a controlled testnet or isolated fixture, verify normal sponsored payments and rejection of padded calldata and client-supplied access lists. Record the running dependency version and sponsorship decision without exposing wallet keys or using production funds.
- Retain evidence. Preserve asset and owner identifiers, the applicability decision, before-and-after versions, change approval, installation output, validation results, and any exception or rollback record.
Operational Cautions
Gas, fee and request-size caps did not prevent the vendor's demonstrated cases; they are not substitutes for the fix. The reported fee multipliers came from the advisory's experiments and are not measurements of your service. Review anomalous spending separately, since an update cannot reverse paid transaction fees.
Evidence To Retain
- Exact product, release stream, package or application version, enabled feature, environment, and accountable owner.
- UTC timestamps, authority revision, approved change record, installer or package-manager output, and resulting version.
- Relevant logs and monitoring evidence, test results, exceptions, compensating controls, and rollback decisions.
Related TechGeeks Resources
Authoritative References
Correction policy: If the authority changes affected versions, fixed versions, severity, exploitation information, mitigations, or required action, TechGeeks will update this notice and its verification date.
