Outgoing datagram buffer accounting can panic the sender in quinn-proto

Exploitation

No confirmed exploitation recorded. Patch Next marks exploitation only from CISA KEV.

CVSS

7.5 · CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

EPSS

No dated EPSS signal available.

As published by the source; long descriptions are shortened.

The limit on memory used to buffer outgoing datagrams, introduced in 0.11.17, subtracted an evicted datagram's size from the buffered byte counter twice when `Datagrams::send` was called with `drop = true` (as `Connection::send_datagram` in the `quinn` crate does) while the buffer was full. Under sustained eviction the counter drifts below its true value: debug builds panic with an integer underflow, while release builds wrap the counter, drain the whole queue, and then panic on a desynchronization check in a later `send` call. In `quinn`, this panic occurs while the connection lock is held, poisoning it and causing a double panic (and thus an abort) when the connection is dropped. This can be triggered without a malicious peer, by an application that sends a burst of datagrams and then idles. It can also be triggered by a peer that keeps the connection alive with PING frames while withholding acknowledgements, so that the sender's congestion window stays closed and the outgoing…

Published by the source

14 Sep 2026, 12:00 UTC

Last modified by the source

12 Oct 2026, 18:15 UTC

Source last checked

23 Oct 2026, 22:04 UTC

1. Revision 1 · created · 24 Oct 2026

   Published from osv record RUSTSEC-2026-0343

Preview the exact text before you copy it. Commands are read-only suggestions; review them before running anything.

# Patch Next advisory brief: GHSA-ppcp-v39w-8jq2

Advisory: Outgoing datagram buffer accounting can panic the sender in quinn-proto
IDs: GHSA-ppcp-v39w-8jq2
Record: https://patchnext.com/advisories/rustsec-2026-0343 (revision 1, source checked 23 Oct 2026, 22:04 UTC)
Inventory: none attached. This brief comes from a public page and does not say whether any deployment is affected.
Severity: High (CVSS 7.5)
Exploitation: no confirmed exploitation recorded. Patch Next confirms exploitation only from CISA KEV.
Vendor response: Vendor fix available; fixed versions by package: quinn-proto 0.11.18. A vendor fix does not mean a deployment is fixed.

## Affected components
- crates.io quinn-proto: affected >= 0.11.17, < 0.11.18; fixed in 0.11.18

## Suggested inspection (read-only)
- crates.io quinn-proto: check the installed version with your package manager.

## Supported action
Upgrade each affected component to a fixed version on its release line. For a transitive dependency, upgrade the parent package or add an override or constraint, then regenerate the lockfile. Redeploy every environment that ran an affected version.

## Required regression checks
- Run the test suite and a production build.
- Exercise the features that depend on quinn-proto.
- Repeat the inspection and confirm that only fixed versions remain installed.

## Rollback considerations
- Keep the previous lockfile and deployment artifact. Rolling back reinstates the vulnerable version, so apply any documented mitigation while you fix forward.

## Unresolved questions
- Which deployments run an affected version?
- Exploitation status can change. Check again before lowering the priority.
- Mark the work resolved only after the fixed version is verified in production.

## Sources
- Verified: https://osv.dev/vulnerability/RUSTSEC-2026-0343 (OSV record RUSTSEC-2026-0343 lists affected ranges: crates.io quinn-proto >=0.11.17 <0.11.18 (fixed))

Commands are suggestions: review each one before running it.