Zebra's Block Validator Undercounts Coinbase and P2SH Sigops

Exploitation

No confirmed exploitation recorded. Patch Next marks exploitation only from CISA KEV.

CVSS 4.0

9.2 · CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:H/VA:N/SC:N/SI:H/SA:N · score source

EPSS

• CVE-2026-44498: 0.28% estimated exploitation activity in the next 30 days; percentile 20.88 (FIRST EPSS, 2026-11-03). This is a model estimate, not proof of exploitation or customer exposure.

As published by the source; long descriptions are shortened.

Zebra's block validator undercounts transparent signature operations against the 20000-sigop block limit (MAXBLOCKSIGOPS), allowing it to accept blocks that zcashd rejects with bad-blk-sigops. A miner who produces such a block can split the network: Zebra nodes follow the offending chain while zcashd nodes do not. Two distinct undercounts: A: Coinbase Hidden Legacy Sigops zcashd's GetLegacySigOpCount() includes the coinbase input's scriptSig. Zebra's Sigops impl skipped the coinbase input entirely, so up to ~98 sigops (the 100-byte coinbase script length cap, less the height prefix) could be hidden inside the coinbase scriptSig without being charged against the block limit. B: Aggregate P2SH Sigops. zcashd's GetP2SHSigOpCount() parses each P2SH input's redeem script with accurate=true and sums those sigops into the block-wide total via ConnectBlock. The check is per-block, not per-transaction, and the limit applies regardless of who mines the offending block — a miner just needs to…

Published by the source

7 May 2026, 20:54 UTC

Last modified by the source

13 May 2026, 13:28 UTC

Source last checked

26 Oct 2026, 15:42 UTC

1. Revision 1 · created · 26 Oct 2026

   Published from ghsa record GHSA-jv4h-j224-23cc

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# Patch Next advisory brief: CVE-2026-44498

Advisory: Zebra's Block Validator Undercounts Coinbase and P2SH Sigops
IDs: CVE-2026-44498, GHSA-jv4h-j224-23cc
Record: https://patchnext.com/advisories/cve-2026-44498 (revision 1, source checked 26 Oct 2026, 15:42 UTC)
Inventory: none attached. This brief comes from a public page and does not say whether any deployment is affected.
Severity: Critical (CVSS 9.2)
Exploitation: no confirmed exploitation recorded. Patch Next confirms exploitation only from CISA KEV.
Vendor response: Vendor fix available; fixed versions by package: zebrad 4.4.0. A vendor fix does not mean a deployment is fixed.

## Affected components
- crates.io zebrad: affected < 4.4.0; fixed in 4.4.0

## Suggested inspection (read-only)
- crates.io zebrad: check the installed version with your package manager.

## Supported action
Upgrade each affected component to a fixed version on its release line. For a transitive dependency, upgrade the parent package or add an override or constraint, then regenerate the lockfile. Redeploy every environment that ran an affected version.

## Required regression checks
- Run the test suite and a production build.
- Exercise the features that depend on zebrad.
- Repeat the inspection and confirm that only fixed versions remain installed.

## Rollback considerations
- Keep the previous lockfile and deployment artifact. Rolling back reinstates the vulnerable version, so apply any documented mitigation while you fix forward.

## Unresolved questions
- Which deployments run an affected version?
- Exploitation status can change. Check again before lowering the priority.
- Mark the work resolved only after the fixed version is verified in production.

## Sources
- Verified: https://github.com/advisories/GHSA-jv4h-j224-23cc (GitHub-reviewed advisory GHSA-jv4h-j224-23cc lists affected ranges: crates.io zebrad >=0 <4.4.0)

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