CVE-2026-104432: Zebra before 6.3.0 False Readiness via Discarded One-Hash FindBlocks Response

Severity: medium (CVSS 5.3 v3.1)
Exploited in the wild: not listed in CISA KEV
EPSS: 0.3% probability of exploitation in the next 30 days
Public exploit or detection template: none known
Published: 2026-10-02 · updated 2026-10-06
Weakness: CWE-754

Description

Zebra before 6.3.0 contains an improper exceptional condition check in ChainSync::obtain_tips that discards valid one-hash FindBlocks responses, falsely reporting close-to-tip status. Peers returning only the next block hash cause a zero-length sync sample, making the /ready endpoint return 200 OK while the node remains behind the tip.

Affected products

ZcashFoundation zebra: before 6.3.0 — fixed in 6.3.0

How to fix

Upgrade to a fixed version: ZcashFoundation zebra 6.3.0. Check the vendor advisory for mitigations.

References

https://github.com/ZcashFoundation/zebra/security/advisories/GHSA-h8m8-844p-v3m9
https://www.vulncheck.com/advisories/zebra-before-6.3.0-false-readiness-via-discarded-one-hash-findblocks-response

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