CVE-2026-82751 ZenHive CVE debrief

Who should care

Defenders responsible for ZenHive mpp deployments, particularly those using sponsored payments, should assess exposure and prioritize remediation. Defenders should prioritize verifying and remediating this vulnerability in ZenHive mpp versions from 0.2.0 before 0.16.1, as it allows for potential gas cost inflation and unauthorized access key provisioning.

Why it matters

Defenders should prioritize verifying and remediating this vulnerability in ZenHive mpp versions from 0.2.0 before 0.16.1, as it allows for potential gas cost inflation and unauthorized access key provisioning.

• Potential for significant gas cost inflation
• Unauthorized access key provisioning
• Increased risk for sponsored payment abuse

Technical summary

The vulnerability allows an unauthenticated remote client to inflate the fee-payer's gas cost per sponsored payment by a large multiplier and to have the sponsor pay for provisioning an access key on the client's own account. This issue affects mpp: from 0.2.0 before 0.16.1. The server sponsors Tempo payments, MPP.Methods.Tempo.FeePayerPolicy.measure/3 in lib/mpp/methods/tempo/fee_payer_policy.ex bounds the gas fields, the fee budget, the validity window and the access list of the client-signed 0x76 envelope, but does not check whether the envelope carries the optional key_authorization field.

Defensive priority

Defenders should prioritize verifying and remediating this vulnerability in ZenHive mpp versions from 0.2.0 before 0.16.1.

Recommended defensive actions

• Verify and remediate ZenHive mpp versions from 0.2.0 before 0.16.1
• Review and update access controls for sponsored payments
• Monitor for suspicious activity related to gas cost inflation
• Review compensating controls for exposed systems while remediation is scheduled and verified
• Check relevant monitoring, detection, and logs for exposed assets that need extra review
• Track exceptions, retest remediated assets, and close the item only after evidence is documented
• Confirm whether affected product deployments exist in managed environments and assign an owner for follow-up

Evidence notes

The CVE record and NVD entry provide details on the vulnerability, including its description and affected versions. The vulnerability allows an unauthenticated remote client to inflate the fee-payer's gas cost per sponsored payment by a large multiplier and to have the sponsor pay for provisioning an access key on the client's own account. Defenders should verify and remediate this vulnerability in ZenHive mpp versions from 0.2.0 before 0.16.1. The reporter provided a default example of one key with three token limits, which raises the sponsored cost from about 46,587 gas to about 1,808,700 gas.

Sources and references

Methodology and review provenance

AI-assisted synthesis based on stored public vulnerability evidence. System validation, approval state, and publication status do not by themselves establish human review of this revision. PatchSiren helps prioritize defensive review and does not prove exposure or remediation on any system.