CVE-2026-104421— Zebra before 6.2.1 Block Download Denial of Service via KnownBlock SentHashes Lockout
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.
Zebra 6.2.1 版本之前存在一个不完整的清理漏洞，该漏洞允许未认证的对等节点通过在被拒绝的哈希（SentHashes）中遗留无效哈希，从而阻止有效区块的下载。攻击者可以发送一个在上下文上无效的区块，该区块与诚实区块共享相同的区块头哈希，导致 跳过该诚实区块，使节点落后于最新区块高度（tip）。
Possible ATT&CK Techniques 1 AI
T1499 · Endpoint Denial of ServiceAffected Version Matrix 2
| Vendor | Product | Version Range | Status |
|---|---|---|---|
| ZcashFoundation | zebra | < 6.2.1 |
affected |
6.2.1 |
unaffected |
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I. Basic Information for CVE-2026-104421
Vulnerability Information
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Vulnerability Title
Zebra before 6.2.1 Block Download Denial of Service via KnownBlock SentHashes Lockout
Source: CVE Program / CVE List V5
Vulnerability Description
Zebra before 6.2.1 contains an incomplete cleanup vulnerability that allows unauthenticated peers to block downloading of valid blocks by leaving rejected hashes in SentHashes. Attackers can send a contextually invalid block sharing an honest block's header hash, causing Request::KnownBlock to skip the honest block and keep nodes behind the tip.
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
清理环节不完整
Source: CVE Program / CVE List V5
Affected Products
| Vendor | Product | Affected Versions | CPE | Subscribe |
|---|---|---|---|---|
| ZcashFoundation | zebra | 0 ~ 6.2.1 | - |
|
II. Public POCs for CVE-2026-104421
| # | POC Description | Source Link | Shenlong Link |
|---|
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Vendor Advisories for CVE-2026-104421 (2)
Same Patch Batch · ZcashFoundation · 2026-10-02 · 18 CVEs total
| CVE-2026-104423 | 7.5 HIGH | Zebra before 6.2.1 Denial of Service via Uncapped V6 Shielded Proof Verification |
| CVE-2026-104430 | 7.5 HIGH | Zebra 4.5.0 Consensus Split via P2SH Sigop Overcount |
| CVE-2026-104431 | 7.5 HIGH | Zebra before 6.0.0 Denial of Service via Synchronous Script FFI Verification |
| CVE-2026-104422 | 7.5 HIGH | Zebra before 6.3.0 Block Sync Denial of Service via Coinbase scriptSig Rewrite |
| CVE-2026-104435 | 7.4 HIGH | Zebra 4.4.0 Consensus Divergence via V5 SIGHASH_SINGLE Without Output |
| CVE-2026-104437 | 7.4 HIGH | Zebra before 4.4.0 Consensus Split via SIGHASH_SINGLE Missing-Output Handling |
| CVE-2026-104434 | 6.5 MEDIUM | Zebra before 8.0.0 Denial of Service via z_listunifiedreceivers RPC |
| CVE-2026-104426 | 5.9 MEDIUM | Zebra before 6.1.0 Quadratic Complexity DoS via Block Transparent Value Check |
| CVE-2026-104427 | 5.9 MEDIUM | Zebra before 6.1.0 Chain Stall via Stale parent_error_map Entry |
| CVE-2026-104428 | 5.3 MEDIUM | Zebra before 11.0.0 Denial of Service via getblock Verbosity 2 |
| CVE-2026-104432 | 5.3 MEDIUM | Zebra before 6.3.0 False Readiness via Discarded One-Hash FindBlocks Response |
| CVE-2026-104425 | 5.3 MEDIUM | Zebra before 6.1.0 Batch-Verification Poisoning DoS via Unattributed Pushed Transactions |
| CVE-2026-104420 | 5.3 MEDIUM | Zebra before 6.3.0 Peer Misbehavior Ban Bypass via Gossiped Blocks |
| CVE-2026-104429 | 5.3 MEDIUM | Zebra before 6.0.0-rc.0 Per-Peer Mempool Admission Bypass via P2P tx Messages |
| CVE-2026-104419 | 4.8 MEDIUM | Zebra before 6.3.0 Honest Peer Banning via Far-Ahead FindBlocks Hashes |
| CVE-2026-104424 | 3.7 LOW | Zebra before 6.1.0 Incorrect Block Size Calculation in getblocktemplate |
| CVE-2026-104436 | 3.7 LOW | Zebra before 4.5.0 CPU Amplification via Uncapped getblocks/getheaders Locator Length |
IV. Related Vulnerabilities
Same product: zebra
-
CVE-2026-104437
Zebra before 4.4.0 Consensus Split via SIGHASH_SINGLE Missin -
CVE-2026-104436
Zebra before 4.5.0 CPU Amplification via Uncapped getblocks/ -
CVE-2026-104434
Zebra before 8.0.0 Denial of Service via z_listunifiedreceiv -
CVE-2026-104435
Zebra 4.4.0 Consensus Divergence via V5 SIGHASH_SINGLE Witho -
CVE-2026-104432
Zebra before 6.3.0 False Readiness via Discarded One-Hash Fi
Same vendor: ZcashFoundation
-
CVE-2026-104437
Zebra before 4.4.0 Consensus Split via SIGHASH_SINGLE Missin -
CVE-2026-104436
Zebra before 4.5.0 CPU Amplification via Uncapped getblocks/ -
CVE-2026-104434
Zebra before 8.0.0 Denial of Service via z_listunifiedreceiv -
CVE-2026-104435
Zebra 4.4.0 Consensus Divergence via V5 SIGHASH_SINGLE Witho -
CVE-2026-104431
Zebra before 6.0.0 Denial of Service via Synchronous Script
Same weakness: CWE-459
-
CVE-2026-104427
Zebra before 6.1.0 Chain Stall via Stale parent_error_map En -
CVE-2026-95326
Chrome 154.0.8037.57前蓝牙资源清理不当漏洞 -
CVE-2026-95303
Chrome 154.0.8037.57前SmartCard清理不全漏洞 -
CVE-2026-101100
ag-ui-protocol ag-ui Middleware filter-tool-calls.ts FilterT -
CVE-2026-78437
Apache Tomcat: HTTP/2 DoS via malformed request
V. Comments for CVE-2026-104421
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