CVE-2026-52734 ZEBRA: Unbounded memory leak in mempool download pipeline via timeout path cancel_handles retention
An unauthenticated peer can cause memory exhaustion in the Zcash node by retaining timed-out transactions, leading to a denial of service.
- Exploited in the wild
- Not known
- Login needed
- Not needed
- Attackable
- Over the internet
- Victim action needed
- Not needed
- Fix
- Available
What is CVE-2026-52734?
CVE-2026-52734 is a medium-severity denial of service vulnerability in ZcashFoundation zebra, published on 18 Aug 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.
Official description
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.
Weakness: CWE-401
Which versions are affected by CVE-2026-52734?
2 open source packages ship an affected version, including zebrad.
| Package | Affected | Fixed in |
|---|---|---|
zebrad crates.io | All versions | 4.5.0 |
zebrad crates.io | All versions | 4.5.0 |
How do I fix CVE-2026-52734?
Upgrade zebrad to 4.5.0 or later.
Upgrade, then put limits on request size, rate and nesting depth so one client cannot exhaust the service. More about Denial of service.
Is CVE-2026-52734 being exploited?
There is no known exploitation of CVE-2026-52734 in the wild and no public exploit code.
Sources
Also known as GHSA-65jj-fmw8-468q.