# RUSTSEC-2026-0231: Relay authentication challenges can exhaust memory

> A malicious relay can exhaust client memory by flooding authentication challenges, causing denial of service in the Rust Nostr SDK.

- **Severity:** Not scored
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Over the internet
- **Victim action needed:** Not needed
- **Fix available:** Yes
- **Published:** 1 Aug 2026

## What is RUSTSEC-2026-0231?

RUSTSEC-2026-0231 is a denial of service vulnerability in nostr-relay-pool, published on 1 Aug 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.

### Official description

The SDK forwarded every NIP-42 `AUTH` challenge received from a relay through an
unbounded command queue. Challenge handling can wait for an asynchronous signer or
user interaction, so receiving challenges was substantially faster than completing
the corresponding authentication work.

A malicious relay could continuously send new challenges without authenticating or
delivering valid events. Every value remained queued, causing memory use and pending
signer operations to grow without a fixed limit until the client became unavailable.
The issue does not allow the relay to forge a signature or learn the client's private
key.

The SDK now coalesces pending challenges through a latest-value channel. NIP-42 makes
an earlier challenge invalid when the relay sends a new one, so replacing pending
work preserves the only challenge that can still be answered while keeping memory
use bounded.

## Which versions are affected by RUSTSEC-2026-0231?

1 open source package ship an affected version, including nostr-relay-pool.


| Package | Ecosystem | Affected | Fixed in |
| --- | --- | --- | --- |
| `nostr-relay-pool` | crates.io | From 0.0.0-0 | 0.44.3 |

## How do I fix RUSTSEC-2026-0231?

Upgrade nostr-relay-pool to 0.44.3 or later.

## Is RUSTSEC-2026-0231 being exploited?

There is no known exploitation of RUSTSEC-2026-0231 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for RUSTSEC-2026-0231 and fix it if it is affected.

What it is: RUSTSEC-2026-0231 is a denial of service vulnerability in nostr-relay-pool, published on 1 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 RUSTSEC-2026-0231 in the wild and no public exploit code.

Affected packages and fixed versions:
- nostr-relay-pool (crates.io): affected from 0.0.0-0; fixed in 0.44.3

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/RUSTSEC-2026-0231/ (Markdown: https://insights.sbomify.com/RUSTSEC-2026-0231/index.md)
```

## Sources

- OSV: https://osv.dev/vulnerability/RUSTSEC-2026-0231

---
From sbomify Insights: https://insights.sbomify.com/RUSTSEC-2026-0231/
Summaries are generated and may contain mistakes; the official description above is the record.