Sync stalling via peer-attribution failure
Published Aug 18, 2026 · Updated Aug 18, 2026
Denial of service in Zcash Foundation Zebra before 4.5.0 allows remote attackers to stall synchronization via crafted P2P block responses. In the sync download pipeline, AboveLookaheadHeightLimit originally carried only the block height and hash, so handle_block_response could not attribute the above-lookahead block to the advertising peer and instead sent the error into the global restart path. A post-handshake unauthenticated peer can repeat the small-inventory-plus-block cycle indefinitely, canceling unrelated in-flight downloads and imposing about 67 seconds of restart delay per cycle without corrupting chain state.
Summary
What happened
Denial of service in Zcash Foundation Zebra before 4.5.0 allows remote attackers to stall synchronization via crafted P2P block responses. In the sync download pipeline, AboveLookaheadHeightLimit originally carried only the block height and hash, so handle_block_response could not attribute the above-lookahead block to the advertising peer and instead sent the error into the global restart path. A post-handshake unauthenticated peer can repeat the small-inventory-plus-block cycle indefinitely, canceling unrelated in-flight downloads and imposing about 67 seconds of restart delay per cycle without corrupting chain state.
The record
- CVE
- CVE-2026-52737
- Published
- Aug 18, 2026
- Updated
- Aug 18, 2026
- Vendor
- Zcash Foundation
- Product
- zebra-consensus
- Classifications
- CWE-345, T1499
- Attack vector
- network
- Privileges
- unauthenticated
Timeline
How it unfolded
- Aug 18, 2026CVE publishedPublication date reported by the CVE source.
- Aug 18, 2026Record updatedLatest update available in the CVE record.
Exploitability
Present is not the same as exploitable
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Is a vulnerable build present?
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- Affected versionversion=< 7.0.0
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What is affected?
Published CVSS scores
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Attacks
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Weakness, pattern, technique
Public exploit references
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Technologies
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Your stack
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