CVE-2026-104436
Deferred Deferred - Pending Action

BaseFortify

Publication date: 2026-10-02

Last updated on: 2026-10-02

Assigner: VulnCheck

Description
Zebra before 4.5.0 contains an uncontrolled resource consumption vulnerability that allows remote P2P peers to exhaust blocking-pool threads by sending oversized block locator vectors. Attackers can send getblocks or getheaders messages with up to 65,535 locator hashes, triggering per-hash chain lookups that degrade block validation, RPC, and mempool performance.

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Meta Information

Published
2026-10-02
Last Modified
2026-10-02
Generated
2026-10-19
AI Q&A
2026-10-02
EPSS Evaluated
2026-10-18
NVD
CVE-2026-104436
EUVD
EUVD-2026-91446

Affected Vendors & Products

Showing 2 associated CPEs
Vendor Product Version / Range
ZcashFoundation zebra 0
ZcashFoundation zebra 0

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Exploitability

CWE
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KEV
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CWE ID Description
CWE-770 The product allocates a reusable resource or group of resources on behalf of an actor without imposing any intended restrictions on the size or number of resources that can be allocated.

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Executive Summary

This vulnerability in Zebra before 4.5.0 allows remote P2P peers to cause CPU exhaustion by sending oversized block locator vectors in getblocks or getheaders messages. Attackers can include up to 65,535 locator hashes, forcing excessive chain lookups that degrade block validation, RPC, and mempool performance.

Detection Guidance

Monitor Zebra node logs for excessive CPU usage or repeated getblocks/getheaders requests with large locator vectors. Check for blocked threads in blocking-pool during P2P message handling. Use network monitoring tools to detect peers sending oversized block locator vectors.

Impact Analysis

This vulnerability can degrade system performance by consuming CPU resources through excessive chain lookups. It may slow down block validation, RPC responses, and mempool operations, especially under sustained attack from multiple peers. Exploitation requires significant attacker bandwidth and multiple Sybil peers.

Compliance Impact

This vulnerability does not directly affect compliance with GDPR or HIPAA as it pertains to resource exhaustion in a blockchain node software (Zebra). However, if exploited, degraded performance could indirectly impact systems handling sensitive data by reducing availability or response times, potentially violating availability requirements in GDPR (Article 32) or HIPAA (Security Rule). No direct compliance violations are specified in the provided context.

Mitigation Strategies

Upgrade Zebra to version 4.5.0 or later to apply the patch that caps locator vector length at 101 entries. If upgrading is not immediately possible, restrict P2P connections to trusted peers or disable P2P functionality temporarily.

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