CVE-2026-52739: ZcashFoundation Zebra process abort via repeated shielded transactions

CVE-2026-52739 · Severity: medium · CVSS 5.9 · Published 2026-08-18

Zebra, a Zcash node implementation, is vulnerable to a denial-of-service attack that can crash the software. A malicious actor can trigger this by mining or broadcasting specific types of transactions that cause the node to encounter an internal error and shut down. This affects the availability of the node, requiring a manual restart to restore service.

Technologies: zebra-state (crates.io), zebrad (crates.io). Vendors: crates.io.

Quick answers

Is CVE-2026-52739 exploited in the wild?
No. Junglewise Threat Intelligence has no report of CVE-2026-52739 being exploited in the wild.
How severe is CVE-2026-52739?
Medium severity, with a CVSS score of 5.9, published 18 August 2026.
Which products and versions are affected?
zebra-state (crates.io) <= 6.0.0, SEMVER:introduced=0,fixed=7.0.0; zebrad (crates.io) <= 4.4.1, SEMVER:introduced=0,fixed=4.5.0.
Is there a fix for CVE-2026-52739?
Yes. zebra-state (crates.io): upgrade to 7.0.0 or later; zebrad (crates.io): upgrade to 4.5.0 or later. Junglewise finds every place you run it, drafts the upgrade and applies it once you approve.
How is CVE-2026-52739 attacked?
It is attacked over the network, in a software library.
Am I affected by CVE-2026-52739?
Check whether you run zebra-state (crates.io) or zebrad (crates.io) 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

  • zebra-state (crates.io): upgrade to 7.0.0 or later
    cargo update -p zebra-state
  • zebrad (crates.io): upgrade to 4.5.0 or later
    cargo update -p zebrad

Technical details

A vulnerability exists in the `Chain::push` function within the `zebra-state` non-finalized state logic. The component updates the transaction-location index (`tx_loc_by_hash`) using an `assert_eq!` check for uniqueness before performing shielded-nullifier validation. If a child block repeats a shielded transaction from its non-finalized parent, the assertion fails and triggers a `panic = "abort"`, terminating the process. Attackers can exploit this by mining two consecutive blocks or by broadcasting a transaction to the mempool and mining a follow-up block after an honest miner includes it. The issue is fixed in `zebrad` v4.5.0 and `zebra-state` v7.0.0 by replacing the assertion with proper error handling.

Affected products

  • ZcashFoundation zebrad <= 4.4.1
  • ZcashFoundation zebra-state <= 6.0.0

Identifiers

  • CVE-2026-52739
  • GHSA-hhm7-qrv5-h4r6

Timeline

  • 2026-05-29: disclosed: Initial report by haxatron
  • 2026-07-02: advisory: GitHub Advisory published

References

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