ZcashFoundation Zebra up to 4.4.9 P2P Message getblocks/getheaders locator hashes resource consumption

Summaryinfo

A vulnerability was found in ZcashFoundation Zebra up to 4.4.9. It has been rated as problematic. Impacted is the function getblocks/getheaders of the component P2P Message Handler. This manipulation of the argument locator hashes causes resource consumption. This vulnerability is tracked as CVE-2026-104436. The attack is possible to be carried out remotely. No exploit exists. Upgrading the affected component is advised.

Detailsinfo

A vulnerability has been found in ZcashFoundation Zebra up to 4.4.9 and classified as problematic. Affected by this vulnerability is the function getblocks/getheaders of the component P2P Message Handler. The manipulation of the argument locator hashes with an unknown input leads to a resource consumption vulnerability. The CWE definition for the vulnerability is CWE-400. The product does not properly control the allocation and maintenance of a limited resource, thereby enabling an actor to influence the amount of resources consumed, eventually leading to the exhaustion of available resources. As an impact it is known to affect availability. The summary by CVE is:

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.

The advisory is shared at github.com. This vulnerability is known as CVE-2026-104436 since 10/02/2026. The exploitation appears to be easy. The attack can be launched remotely. The exploitation doesn't need any form of authentication. Technical details are known, but no exploit is available. MITRE ATT&CK project uses the attack technique T1499 for this issue.

Upgrading to version 4.5.0 eliminates this vulnerability.

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Productinfo

Vendor

• ZcashFoundation

Name

• Zebra

Version

• 4.4.0
• 4.4.1
• 4.4.2
• 4.4.3
• 4.4.4
• 4.4.5
• 4.4.6
• 4.4.7
• 4.4.8
• 4.4.9

Website

• Product: https://github.com/ZcashFoundation/zebra/

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