CVE-2026-104424
Received Received - Intake

Zebra Node Incorrect ZIP-317 Block Template Size Calculation

Publication date: 2026-10-02

Last updated on: 2026-10-02

Assigner: VulnCheck

Description
Zebra before 6.1.0 contains an incorrect calculation vulnerability in its ZIP-317 block template selector that omits header and transaction-count size from the block budget. Attackers can place valid selectable transactions in a victim miner's mempool to shape templates into oversized blocks, causing rejection and wasted proof-of-work.

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Meta Information

Published
2026-10-02
Last Modified
2026-10-02
Generated
2026-10-02
AI Q&A
2026-10-02
EPSS Evaluated
N/A
NVD
CVE-2026-104424
EUVD
EUVD-2026-91435

Affected Vendors & Products

Showing 1 associated CPE
Vendor Product Version / Range
zebra zebra to 6.1.0 (exc)

Helpful Resources

Exploitability

CWE
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KEV
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CWE ID Description
CWE-131 The product does not correctly calculate the size to be used when allocating a buffer, which could lead to a buffer overflow.

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Executive Summary

This vulnerability affects Zebra, a Zcash node software implementation, up to version 6.0.0. It involves incorrect block template generation where the transaction selector does not account for the serialized block header and transaction-count field sizes. This omission can create oversized invalid blocks exceeding the 2,000,000-byte consensus limit, wasting miners' proof-of-work.

Detection Guidance

To detect this vulnerability, check if your Zebra node is running a version prior to 6.1.0. Use the command 'zebrad --version' to verify the installed version. If the version is below 6.1.0, the system is vulnerable. Additionally, monitor for oversized block rejections in mining logs, which may indicate exploitation attempts.

Impact Analysis

If you are a miner using Zebra versions before 6.1.0, an attacker could exploit this by placing transactions in your mempool to shape block templates into oversized blocks. These blocks would be rejected by the network, causing you to waste computational effort and lose potential mining rewards.

Compliance Impact

This vulnerability does not directly affect compliance with GDPR, HIPAA, or similar standards. It impacts mining operations by causing wasted proof-of-work due to rejected oversized blocks, which is unrelated to data protection or privacy regulations.

Mitigation Strategies

Upgrade Zebra to version 6.1.0 or later immediately. This version includes the fix for the block template size calculation. If upgrading is not possible, consider temporarily disabling mining operations until the update is applied to prevent potential losses from oversized block rejections.

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