# CVE-2026-52732: ZEBRA: Mempool transaction admission denial via single-peer inbound queue saturation

> An unauthenticated peer can saturate Zebra's mempool queue, causing denial of service for transaction processing.

- **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:** 18 Aug 2026
- **Also known as:** GHSA-4fc2-h7jh-287c

## What is CVE-2026-52732?

CVE-2026-52732 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, one unauthenticated P2P peer can monopolize all 25 MAX_INBOUND_CONCURRENCY slots in Zebra's inbound mempool download and verification pipeline. In zebrad/src/components/mempool/downloads.rs, the bounded queue was shared globally without per-peer accounting, while peer identity was not carried through Gossip and FullQueue responses were mapped to Response::Nil instead of reaching overload disconnection handling. An attacker can advertise fake transaction identifiers and remain silent so each task holds a slot until TRANSACTION_DOWNLOAD_TIMEOUT, then periodically refill the queue as slots expire. While saturated, honest peer transactions and local sendrawtransaction requests are rejected with MempoolError::FullQueue, although block validation and synchronization continue. This issue is fixed in version 4.5.0.

Weakness: CWE-770 (Allocation of Resources Without Limits or Throttling)

## Which versions are affected by CVE-2026-52732?

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-2026-52732?

Upgrade zebrad to 4.5.0 or later.

## Is CVE-2026-52732 being exploited?

It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-52732 exists.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-52732 and fix it if it is affected.

What it is: CVE-2026-52732 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: It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-52732 exists.

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-2026-52732/ (Markdown: https://insights.sbomify.com/CVE-2026-52732/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-52732
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-52732
- OSV: https://osv.dev/vulnerability/CVE-2026-52732

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-52732/
Summaries are generated and may contain mistakes; the official description above is the record.