-----BEGIN PGP SIGNED MESSAGE-----
Hash: SHA512

0xCERT Security Advisory 0xCERT-2026-0206
============================================================

Advisory-ID:  0xCERT-2026-0206
Severity:     Medium
Published:    2026-07-02T19:44:24.000Z
Updated:      2026-10-08T22:47:33.548Z
Chains:       n/a
URL:          https://www.0xcert.com/advisory/0xCERT-2026-0206

Title: Zebra has sync restart poisoning from single unauthenticated peer via above-lookahead block

Summary
- -------
Zebra has sync restart poisoning from single unauthenticated peer via above-lookahead block. You are affected if: 1. You run zebrad up to and including v4.4.1. 2. Your node accepts inbound P2P connections and is syncing or catching up to the chain tip. A malicious peer can answer Zebra's outbound getblocks/FindBlocks request with a small two-hash inventory, then serve a syntactically valid block whose coinbase height is far above the victim's local tip.

Details
- -------
Summary
You are affected if: 1. You run zebrad up to and including v4.4.1. 2. Your node accepts inbound P2P connections and is syncing or catching up to the chain tip. A malicious peer can answer Zebra's outbound getblocks/FindBlocks request with a small two-hash inventory, then serve a syntactically valid block whose coinbase height is far above the victim's local tip.

Affected
- - zebra-consensus (rust) <= 6.0.0 — fixed in 7.0.0
- - zebrad (rust) <= 4.4.1 — fixed in 4.5.0

Severity
Medium, as rated by the upstream advisory.

Recommended actions
- - Upgrade zebra-consensus to 7.0.0 or later
- - Upgrade zebrad to 4.5.0 or later

Source & attribution
This 0xCERT advisory summarises GHSA-gvjc-3w7c-92jx / CVE-2026-52737 from the GitHub Advisory Database, credited upstream to ipwning, mpguerra, conradoplg, oxarbitrage: https://github.com/advisories/GHSA-gvjc-3w7c-92jx. Details may change; refer to the original source for the authoritative record.

References
- ----------
- - https://github.com/advisories/GHSA-gvjc-3w7c-92jx
- - CVE-2026-52737
- - https://github.com/ZcashFoundation/zebra/security/advisories/GHSA-gvjc-3w7c-92jx

Verify with the 0xCERT OpenPGP key: https://www.0xcert.com/pgp.asc
Fingerprint: 5F94 3ED1 1E50 CF31 2128  C493 CCC7 D9EC 9415 723D

-----BEGIN PGP SIGNATURE-----

wrsEARYKAG0FgmrI9Q4JEDe9Tbcr+ZxrRRQAAAAAABwAIHNhbHRAbm90YXRp
b25zLm9wZW5wZ3Bqcy5vcmfbnP4xlLIV9842lu0JSXqhLLC51NrXZCCUxZxJ
W2Q1XRYhBGCkkFZbJcT5QWu27ze9Tbcr+ZxrAADa3AEAwH2g6S7AwIVGsfaV
tO+GprGIFcbWs4okYkuUBNAOfCcA/R0r9Kf8w+IZ5ZGXWR1iL+8vXMvcMQFX
lXBZswTbytUP
=0FoC
-----END PGP SIGNATURE-----