Vulnerability · Published Oct 2, 2026 · Assigned by VulnCheck

CVE-2026-104431Zebra before 6.0.0 Denial of Service via Synchronous Script FFI Verification

High 7.5

In plain English

A high-severity security flaw in zebra from ZcashFoundation. There are no confirmed reports of exploitation so far. The chance it is exploited in the next 30 days is estimated at 0.3% (higher than 28% of all known vulnerabilities).

Severity (CVSS 3.1)7.5High

Exploit odds (30 days)0.3%top 72.0% of all CVEs

Exploited in the wildNo reportsCISA SSVC: none

Attack toolingNoneno public tooling known

Official description

Zebra before 6.0.0 contains a denial of service vulnerability that allows unauthenticated peers to stall Tokio workers by submitting mempool transactions requiring expensive synchronous script verification. Attackers can send non-standard high-sigop P2SH transactions that reach CachedFfiTransaction::is_valid() before standardness checks, saturating the verifier buffer and rendering the node unresponsive.

Affected products (as reported)

Vendor	Product	Versions
ZcashFoundation	zebra	0 – before 6.0.0

Weakness: CWE-405 · Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

References

GitHub Security Advisory (GHSA-84j3-rw4c-gqmj) vendor-advisory
VulnCheck Advisory: Zebra before 6.0.0 Denial of Service via Synchronous Script FFI Verification third-party-advisory