ZEBRA: Sync restart poisoning from single unauthenticated peer via above-lookahead block

MITRE NVD CVE.ORG JSON API

Summary

CVECVE-2026-52737
StatePUBLISHED
AssignerGitHub_M
Source PriorityCVE Program / NVD first with legacy fallback
Published2026-08-18 20:17:17 UTC
Updated2026-08-18 20:17:17 UTC
DescriptionZEBRA is a Zcash node written entirely in Rust. Prior to 4.5.0, a malicious unauthenticated P2P peer can answer Zebra's outbound getblocks or FindBlocks request with a small two-hash inventory and then serve a syntactically valid block whose coinbase height is far above the local chain tip. In zebrad/src/components/sync/downloads.rs, BlockDownloadVerifyError::AboveLookaheadHeightLimit originally carried only the block height and hash, so handle_block_response could not attribute the failure to the advertising peer. The error then reached the restart-worthy default path in zebrad/src/components/sync.rs, cancelling all in-flight downloads from honest peers and imposing a 67-second sync restart delay on mainnet. Because the peer was neither scored nor disconnected, the peer could repeat the cycle indefinitely with minimal bandwidth and significantly degrade synchronization without corrupting state. This issue is fixed in version 4.5.0.

Risk And Classification

Primary CVSS: v3.1 5.3 MEDIUM from [email protected]

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L

Problem Types: CWE-345 | CWE-345 CWE-345: Insufficient Verification of Data Authenticity

VersionSourceTypeScoreSeverityVector
3.1[email protected]Secondary5.3MEDIUMCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L
3.1CNADECLARED5.3MEDIUMCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L

CVSS v3.1 Breakdown

Attack Vector
Network
Attack Complexity
Low
Privileges Required
None
User Interaction
None
Scope
Unchanged
Confidentiality
None
Integrity
None
Availability
Low

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L

Vendor Declared Affected Products

SourceVendorProductVersionPlatforms
CNA ZcashFoundation Zebra affected < 4.5.0 Not specified
CNA ZcashFoundation Zebra-consensus affected < 7.0.0 Not specified

References

ReferenceSourceLinkTags
github.com/ZcashFoundation/zebra/security/advisories/GHSA-gvjc-3w7c-92jx [email protected] github.com
github.com/ZcashFoundation/zebra/commit/bc64dfe45746a86d14546a0a5a766387... [email protected] github.com
github.com/ZcashFoundation/zebra/commit/1440b43ca7df59aca948090d45117557... [email protected] github.com
github.com/ZcashFoundation/zebra/pull/10647 [email protected] github.com
github.com/ZcashFoundation/zebra/releases/tag/v4.5.0 [email protected] github.com
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