# 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.

- **Severity:** Medium 5.3 (`CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L`)
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Over the internet
- **Victim action needed:** Not needed
- **Fix available:** Yes
- **Published:** 18 Aug 2026
- **Updated:** 19 Aug 2026
- **Also known as:** GHSA-65jj-fmw8-468q

## 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 (Missing Release of Memory after Effective Lifetime)

## Which versions are affected by CVE-2026-52734?

2 open source packages ship an affected version, including zebrad.


| Package | Ecosystem | 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.

## Is CVE-2026-52734 being exploited?

There is no known exploitation of CVE-2026-52734 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-52734 and fix it if it is affected.

What it is: 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.
Exploitation: There is no known exploitation of CVE-2026-52734 in the wild and no public exploit code.

Affected packages and fixed versions:
- zebrad (crates.io): affected all versions; fixed in 4.5.0
- zebrad (crates.io): affected all versions; fixed in 4.5.0

Task:
1. Search the dependency manifests and lockfiles (for example package.json, package-lock.json, requirements.txt, poetry.lock, uv.lock, pom.xml, build.gradle, go.mod, Cargo.lock, Gemfile.lock) and any Dockerfiles for the affected packages, including transitive dependencies.
2. If an affected version is in use, upgrade it to the fixed version for its release line with the project's package manager, so the lockfile is regenerated. Prefer the smallest upgrade that fixes it.
3. If there is no fix, or the upgrade would break the build, do not guess: explain the risk and the safest workaround instead.
4. Run the tests and summarise what changed and why.
5. If nothing in the project is affected, say so and change nothing.

Reference: https://insights.sbomify.com/CVE-2026-52734/ (Markdown: https://insights.sbomify.com/CVE-2026-52734/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-52734
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-52734
- OSV: https://osv.dev/vulnerability/CVE-2026-52734

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-52734/
Summaries are generated and may contain mistakes; the official description above is the record.