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CVE-2026-52737— ZEBRA: Sync restart poisoning from single unauthenticated peer via above-lookahead block

Quick assessment

Affected
ZcashFoundation zebra
Exploitation
No confirmed in-the-wild exploitation; assess based on exposure
Recommended action
Check the vendor advisory and references for a fixed version. If immediate upgrade is impossible, restrict exposure and increase monitoring.

Zcash Foundation ZEBRA是Zcash Foundation基金会的一款区块链网络节点实现。 Zcash Foundation ZEBRA 4.5.0之前版本存在输入验证错误漏洞，该漏洞源于对P2P对等节点提供的区块数据验证不当，导致错误处理路径异常，可能允许未经身份验证的攻击者通过P2P网络干扰同步，显著降低同步性能。

CVSS 5.3 · Medium EPSS 0.20% · P10

Affected Version Matrix 2

VendorProduct Version RangeStatus
ZcashFoundation zebra < 4.5.0 affected
ZcashFoundation zebra-consensus < 7.0.0 affected
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I. Basic Information for CVE-2026-52737

Vulnerability Information
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Vulnerability Title
ZEBRA: Sync restart poisoning from single unauthenticated peer via above-lookahead block
Source: CVE Program / CVE List V5
Vulnerability Description
ZEBRA 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.
Source: CVE Program / CVE List V5
CVSS Information
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L
Source: CVE Program / CVE List V5
Vulnerability Type
对数据真实性的验证不充分
Source: CVE Program / CVE List V5
Vulnerability Title
Zcash Foundation ZEBRA 输入验证错误漏洞
Source: CNNVD (China National Vulnerability Database)
Vulnerability Description
Zcash Foundation ZEBRA是Zcash Foundation基金会的一款区块链网络节点实现。 Zcash Foundation ZEBRA 4.5.0之前版本存在输入验证错误漏洞，该漏洞源于对P2P对等节点提供的区块数据验证不当，导致错误处理路径异常，可能允许未经身份验证的攻击者通过P2P网络干扰同步，显著降低同步性能。
Source: CNNVD (China National Vulnerability Database)
CVSS Information
N/A
Source: CNNVD (China National Vulnerability Database)
Vulnerability Type
N/A
Source: CNNVD (China National Vulnerability Database)

Affected Products

Vendor Product Affected Versions CPE Subscribe
ZcashFoundation zebra < 4.5.0 -
ZcashFoundation zebra-consensus < 7.0.0 -

II. Public POCs for CVE-2026-52737

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III. Intelligence Information for CVE-2026-52737

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Patches & Fixes for CVE-2026-52737 (2)

Vendor Advisories for CVE-2026-52737 (1)

Vendor Pages for CVE-2026-52737 (1)

Same Patch Batch · ZcashFoundation · 2026-08-18 · 10 CVEs total

CVE-2026-52735 9.3 CRITICAL ZEBRA: Consensus divergence via P2SH sigop undercount in pure-Rust disabled-opcode parser
CVE-2026-52736 8.7 HIGH ZEBRA: Block suppression via NU5 same-header body poisoning of sent-hash cache
CVE-2026-52829 7.5 HIGH ZEBRA: IPv4-Mapped Mempool Misbehavior Update Aborts Zebra Address Book
CVE-2026-52738 6.9 MEDIUM ZEBRA: Finalized address balance credit-first overflow on consensus-valid blocks
CVE-2026-52731 6.5 MEDIUM ZEBRA: Full node denial of service via non-ASCII LongPollId in getblocktemplate
CVE-2026-52733 6.5 MEDIUM ZEBRA: Persistent on-disk corruption of Sapling/Orchard subtree roots after chain fork via
CVE-2026-52739 5.9 MEDIUM ZEBRA: Repeated Non-Finalized Shielded Transaction Aborts Zebra Before Duplicate-Nullifier
CVE-2026-52732 5.3 MEDIUM ZEBRA: Mempool transaction admission denial via single-peer inbound queue saturation
CVE-2026-52734 5.3 MEDIUM ZEBRA: Unbounded memory leak in mempool download pipeline via timeout path cancel_handles

IV. Related Vulnerabilities

Same product: zebra
Same vendor: ZcashFoundation
Same weakness: CWE-345

V. Comments for CVE-2026-52737

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