CVE-2026-44498: Zcash Zebra consensus failure via sigop undercounting in block validator

CVE-2026-44498 · Severity: high · CVSS 7.5 · Published 2026-05-07

Zebra, a software implementation of the Zcash cryptocurrency protocol, contains a flaw in how it validates the complexity of transactions within a block. An attacker could create a specially crafted block that Zebra accepts but other Zcash software (like zcashd) rejects, leading to a 'chain split' where different parts of the network disagree on the valid transaction history. This can disrupt the reliability of the payment network and potentially lead to financial loss or service outages for users relying on affected nodes.

Technologies: zebrad (crates.io), Zcash Foundation Zebra. Vendors: crates.io, Zcash Foundation.

Quick answers

Is CVE-2026-44498 exploited in the wild?
No. Junglewise Threat Intelligence has no report of CVE-2026-44498 being exploited in the wild.
How severe is CVE-2026-44498?
High severity, with a CVSS score of 7.5, published 7 May 2026.
Which products and versions are affected?
zebrad (crates.io) < 4.4.0, SEMVER:introduced=0,fixed=4.4.0; Zcash Foundation Zebra < 4.4.0.
Is there a fix for CVE-2026-44498?
Yes. zebrad (crates.io): upgrade to 4.4.0 or later. Junglewise finds every place you run it, drafts the upgrade and applies it once you approve.
How is CVE-2026-44498 attacked?
It is attacked over the network, in a software library.
Am I affected by CVE-2026-44498?
Check whether you run zebrad (crates.io) or Zcash Foundation Zebra at an affected version. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.

How to fix

  • zebrad (crates.io): upgrade to 4.4.0 or later
    cargo update -p zebrad

Technical details

Zebra's block validation logic incorrectly calculates the total number of signature operations (sigops) against the MAX_BLOCK_SIGOPS limit (20,000). Specifically, it fails to count sigops within the coinbase input's scriptSig and fails to accumulate aggregate P2SH redeem script sigops during block validation (only doing so during mempool acceptance). Because the reference implementation (zcashd) correctly enforces these limits, a miner can produce a block that Zebra accepts but zcashd rejects. This results in a consensus failure and a network split between Zebra and zcashd nodes. The issue is fixed in Zebra v4.4.0.

Affected products

  • ZcashFoundation zebra < 4.4.0

Identifiers

  • CVE-2026-44498
  • GHSA-jv4h-j224-23cc

Timeline

  • 2026-05-02: disclosed: Initial disclosure to Zcash Foundation
  • 2026-05-07: advisory: GitHub Advisory published
  • 2026-05-08: other: NVD publication

References

This page as Markdown. Free to reuse under CC BY 4.0 with a link back.