---
id: RUSTSEC-2026-0340
aliases:
  - GHSA-3g6h-r5qx-f6hq
title: >-
  Peer minimum ACK delay can panic quinn-proto when ACK_FREQUENCY transmission
  is enabled
summary: >-
  Peer minimum ACK delay can panic quinn-proto when ACK_FREQUENCY transmission
  is enabled
severity: high
cvss: 7.5
cvssVector: 'CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H'
vendor: quinn-proto
product: quinn-proto
ecosystem: rust
affected:
  - 'quinn-proto >= 0.11.0, < 0.11.18'
patched:
  - quinn-proto 0.11.18
published: '2026-09-14'
updated: '2026-10-12'
sourceUpdated: '2026-10-12T18:15:01.975478256Z'
source: OSV
sourceUrl: 'https://osv.dev/vulnerability/RUSTSEC-2026-0340'
references:
  - url: 'https://crates.io/crates/quinn-proto'
  - url: 'https://rustsec.org/advisories/RUSTSEC-2026-0340.html'
  - url: 'https://github.com/quinn-rs/quinn/pull/2868'
tags:
  - osv
  - rust
ingestedAt: '2026-10-13T11:45:30.200Z'
---

## Overview

When sending ACK_FREQUENCY frames is enabled through
`TransportConfig::ack_frequency_config(Some(..))`, the peer's transport parameters could cause
`AckFrequencyState::candidate_max_ack_delay` to call `Duration::clamp` with a minimum greater
than its maximum, which panics.

For example, a peer advertising a `min_ack_delay` of 100,000 microseconds and a `max_ack_delay`
of 100 milliseconds passes transport parameter validation. At a 5 ms RTT, the lower bound of the
clamp becomes 100 ms while the upper bound is 25 ms, violating the precondition of `clamp` and
panicking while driving the connection. Both automatically derived and explicitly configured
maximum ACK delays use this calculation.

Sending ACK_FREQUENCY frames is disabled by default, so only endpoints that opt in are affected.

The flaw was corrected in 0.11.18 by computing the delay with explicit minimum and maximum bounds
instead of `clamp`.

Thanks to [@zerox80](https://github.com/zerox80) for reporting this issue.

## Affected packages

- `quinn-proto >= 0.11.0, < 0.11.18`

## Remediation

Upgrade to a patched release:

- `quinn-proto 0.11.18`