ZcashFoundation Zebra up to 4.4.x Mempool Downloads downloads.rs Downloads::poll_next memory leak

Summaryinfo

A vulnerability was found in ZcashFoundation Zebra up to 4.4.x and classified as problematic. This issue affects the function Downloads::poll_next of the file zebrad/src/components/mempool/downloads.rs of the component Mempool Downloads. Such manipulation leads to memory leak. This vulnerability is traded as CVE-2026-52734. The attack may be launched remotely. There is no exploit available.

Detailsinfo

A vulnerability, which was classified as problematic, has been found in ZcashFoundation Zebra up to 4.4.x. Affected by this issue is the function Downloads::poll_next of the file zebrad/src/components/mempool/downloads.rs of the component Mempool Downloads. The manipulation with an unknown input leads to a memory leak vulnerability. Using CWE to declare the problem leads to CWE-401. The product does not sufficiently track and release allocated memory after it has been used, which slowly consumes remaining memory. Impacted is availability. CVE summarizes:

ZEBRA is a Zcash node written entirely in Rust. Prior to 4.5.0, an unauthenticated P2P peer can cause the mempool download pipeline to retain transactions after verification reaches the outer RATE_LIMIT_DELAY timeout. In zebrad/src/components/mempool/downloads.rs, Downloads::poll_next removed cancel_handles entries after success and ordinary verification errors, but tokio::time::error::Elapsed did not carry the UnminedTxId needed to remove the timed-out entry. Each retained cancel_handles entry could hold a full Gossip::Tx(UnminedTx), while normal mined-transaction cleanup could not match attacker transactions and no periodic garbage collection or count cap existed. Sustained traffic therefore caused monotonic memory growth until swap pressure degraded the node or the operating system terminated the zebrad process for exhausting memory. This issue is fixed in version 4.5.0.

The advisory is available at github.com. This vulnerability is handled as CVE-2026-52734 since 06/08/2026. The exploitation is known to be easy. The attack may be launched remotely. No form of authentication is required for exploitation. Technical details are known, but there is no available exploit. This vulnerability is assigned to T1499 by the MITRE ATT&CK project.

Upgrading to version 4.5.0 eliminates this vulnerability.

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Productinfo

Vendor

• ZcashFoundation

Name

• Zebra

Version

• 4.0
• 4.1
• 4.2
• 4.3
• 4.4

Website

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

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