CVE-2026-52734: ZcashFoundation zebrad memory leak in mempool download pipeline

CVE-2026-52734 · Severity: medium · CVSS 5.3 · Published 2026-08-18

Zebra, a Zcash node implementation, contains a flaw that causes it to slowly consume all available system memory when processing certain network traffic. This occurs because the software fails to clear temporary data when a transaction verification takes too long to complete. Over time, this memory exhaustion will cause the node to crash or become unresponsive, potentially disrupting the ability to participate in the Zcash network.

Technologies: zebrad (crates.io), Zcash Foundation Zebra. Vendors: crates.io, Zcash Foundation.

Quick answers

Is CVE-2026-52734 exploited in the wild?
No. Junglewise Threat Intelligence has no report of CVE-2026-52734 being exploited in the wild.
How severe is CVE-2026-52734?
Medium severity, with a CVSS score of 5.3, published 18 August 2026.
Which products and versions are affected?
zebrad (crates.io) <= 4.4.1, SEMVER:introduced=0,fixed=4.5.0; Zcash Foundation Zebra <= 4.4.1.
Is there a fix for CVE-2026-52734?
Yes. zebrad (crates.io): upgrade to 4.5.0 or later. Junglewise finds every place you run it, drafts the upgrade and applies it once you approve.
How is CVE-2026-52734 attacked?
It is attacked over the network, in a software library.
Am I affected by CVE-2026-52734?
Check whether you run zebrad (crates.io) or Zcash Foundation Zebra at an affected version. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.

How to fix

  • zebrad (crates.io): upgrade to 4.5.0 or later
    cargo update -p zebrad

Technical details

A memory leak exists in the `Downloads::poll_next()` function within `zebrad/src/components/mempool/downloads.rs`. When a transaction verification task hits the `RATE_LIMIT_DELAY` timeout, the resulting `tokio::time::error::Elapsed` error lacks the transaction ID payload required to remove the entry from the `cancel_handles` map. Consequently, the full deserialized transaction (up to ~9 MB) remains in memory indefinitely. An unauthenticated remote attacker can exploit this by flooding the node with transactions that trigger timeouts, leaking memory at a rate of up to ~685 KB/s per connection. The issue is fixed in version 4.5.0 by ensuring the timeout error path preserves and utilizes the transaction ID for map cleanup.

Affected products

  • ZcashFoundation zebrad <= 4.4.1

Identifiers

  • CVE-2026-52734
  • GHSA-65jj-fmw8-468q

Timeline

  • 2026-05-29: disclosed: Reported via private GitHub Security Advisory
  • 2026-07-02: advisory: GitHub Advisory published
  • 2026-07-02: patched: Version 4.5.0 released

References

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