# CVE-2026-25800: Quinn memory exhaustion in Assembler via out-of-order stream fragments

Source: https://junglewise.ai/threats/cve-2026-25800-quinn-memory-exhaustion-in-assembler-via-out-of-order-stream  
Publisher: Junglewise Threat Intelligence, https://junglewise.ai/threats  
Published: 2026-07-23. Updated: 2026-07-23  
License: CC BY 4.0 with a link back

CVE-2026-25800 · Severity: high · CVSS 7.5 · Published 2026-07-23

Quinn is a software library used by developers to implement the QUIC network protocol in Rust applications. A flaw in how it handles incoming data fragments allows a remote attacker to send specially crafted network traffic that consumes excessive amounts of memory. This can lead to a denial-of-service (DoS) condition where the application crashes or becomes unresponsive due to memory exhaustion.

Technologies: [quinn-proto (crates.io)](https://junglewise.ai/threats/technologies/crates-io-quinn-proto), [Quinn-Rs Quinn-Proto](https://junglewise.ai/threats/technologies/quinn-proto). Vendors: [crates.io](https://junglewise.ai/threats/vendors/crates-io), [Quinn-Rs](https://junglewise.ai/threats/vendors/quinn-rs).

## Quick answers

**Is CVE-2026-25800 exploited in the wild?** No. Junglewise Threat Intelligence has no report of CVE-2026-25800 being exploited in the wild.

**How severe is CVE-2026-25800?** High severity, with a CVSS score of 7.5, published 23 July 2026.

**Which products and versions are affected?** quinn-proto (crates.io) SEMVER:introduced=0.0.0-0,fixed=0.11.15, SEMVER:introduced=0.1.0,fixed=0.11.15; Quinn-Rs Quinn >= 0.1.0, < 0.11.15; Quinn-Rs Quinn-Proto >= 0.1.0, < 0.11.15.

**Is there a fix for CVE-2026-25800?** Yes. quinn-proto (crates.io): upgrade to 0.11.15 or later. Junglewise finds every place you run it, drafts the upgrade and applies it once you approve.

**How is CVE-2026-25800 attacked?** It is attacked over the network, in a software library.

**Am I affected by CVE-2026-25800?** Check whether you run quinn-proto (crates.io), Quinn-Rs Quinn or Quinn-Rs Quinn-Proto at an affected version. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.

## How to fix

- quinn-proto (crates.io): upgrade to 0.11.15 or later

  ```sh
  cargo update -p quinn-proto
  ```


## Technical details

A resource exhaustion vulnerability exists in the `Assembler` component of quinn-proto, which is responsible for reassembling unordered stream fragments. When a `RecvStream` is read in order (e.g., via `AsyncRead`), the library fails to adequately limit the overhead incurred by non-contiguous fragments. An attacker can exploit this by sending fragments that intentionally leave gaps in the early parts of the stream. Because these fragmented chunks cannot be immediately defragmented or cleared, they cause high buffer overhead. This leads to unbounded memory consumption and a subsequent crash (OOM). The issue is fixed in version 0.11.15 by yielding an error when too many gaps are detected in the assembler.

## Affected products

- quinn-rs quinn-proto >= 0.1.0, < 0.11.15
- quinn-rs quinn >= 0.1.0, < 0.11.15

## Identifiers

- CVE-2026-25800
- GHSA-4w2j-m93h-cj5j
- RUSTSEC-2026-0185

## Timeline

- 2026-06-22: patched: Fix merged in pull request 2694 and version 0.11.15 released.
- 2026-06-22: advisory: GitHub Security Advisory GHSA-4w2j-m93h-cj5j published.
- 2026-07-23: disclosed: CVE-2026-25800 published to NVD.

## References

- [https://github.com/quinn-rs/quinn/pull/2694](https://github.com/quinn-rs/quinn/pull/2694)
- [https://github.com/quinn-rs/quinn/security/advisories/GHSA-4w2j-m93h-cj5j](https://github.com/quinn-rs/quinn/security/advisories/GHSA-4w2j-m93h-cj5j)
- [https://rustsec.org/advisories/RUSTSEC-2026-0185.html](https://rustsec.org/advisories/RUSTSEC-2026-0185.html)

## Related threats

- [RUSTSEC-2026-0343 - Outgoing datagram buffer accounting can panic the sender in quinn-proto](https://junglewise.ai/threats/rustsec-2026-0343-outgoing-datagram-buffer-accounting-can-panic-the-270f6598)
- [RUSTSEC-2026-0340 - Peer minimum ACK delay can panic quinn-proto when ACK_FREQUENCY transmission is enabled](https://junglewise.ai/threats/rustsec-2026-0340-peer-minimum-ack-delay-can-panic-quinn-proto-when-ack-29882a7a)
- [quinn-proto denial of service in unordered stream reads](https://junglewise.ai/threats/rustsec-2026-0338-remote-peer-can-panic-quinn-proto-with-zero-length-c5ff03b1)
- [RUSTSEC-2026-0339 - Unbounded growth of pending connection ID retirements in quinn-proto](https://junglewise.ai/threats/rustsec-2026-0339-unbounded-growth-of-pending-connection-id-retirements-0568d867)
- [RUSTSEC-2026-0342 - Zero-length DATAGRAM frames bypass the receive buffer limit in quinn-proto](https://junglewise.ai/threats/rustsec-2026-0342-zero-length-datagram-frames-bypass-the-receive-buffer-613ca2dc)