# CVE-2023-6193: Unbounded queuing of path validation messages in cloudflare-quiche

> An unauthenticated remote attacker can cause excessive resource consumption and denial of service by exploiting unbounded queuing of path validation messages in the quiche library.

- **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:** 12 Dec 2023
- **Updated:** 2 Aug 2024
- **Also known as:** GHSA-w3vp-jw9m-f9pm

## What is CVE-2023-6193?

CVE-2023-6193 is a medium-severity denial of service vulnerability in Cloudflare quiche, published on 12 Dec 2023. An attacker can exploit it over the internet without logging in, with no action from the victim.

### Official description

quiche v. 0.15.0 through 0.19.0 was discovered to be vulnerable to unbounded queuing of path validation messages, which could lead to excessive resource consumption.
QUIC path validation (RFC 9000 Section 8.2) requires that the recipient of a PATH_CHALLENGE frame responds by sending a PATH_RESPONSE. An unauthenticated remote attacker can exploit the vulnerability by sending PATH_CHALLENGE frames and manipulating the connection (e.g. by restricting the peer's congestion window size) so that PATH_RESPONSE frames can only be sent at the slower rate than they are received; leading to storage of path validation data in an unbounded queue. 
Quiche versions greater than 0.19.0 address this problem.

Weakness: CWE-400 (Uncontrolled Resource Consumption)

## Which versions are affected by CVE-2023-6193?

2 open source packages ship an affected version, including quiche. It affects 1 product.


| Package | Ecosystem | Affected | Fixed in |
| --- | --- | --- | --- |
| `quiche` | crates.io | From 0.15.0 | 0.19.1 |
| `quiche` | crates.io | From 0.15.0 | 0.19.1 |

Products: Cloudflare Quiche.

## How do I fix CVE-2023-6193?

Upgrade quiche to 0.19.1 or later.

## Is CVE-2023-6193 being exploited?

There is no known exploitation of CVE-2023-6193 in the wild and no public exploit code.

## Other vulnerabilities in Cloudflare quiche

- [CVE-2025-7054](https://insights.sbomify.com/CVE-2025-7054/): Infinite loop triggered by connection ID retirement (high 8.7)
- [CVE-2026-12523](https://insights.sbomify.com/CVE-2026-12523/): Resource exhaustion in quiche HTTP/3 and QPACK layers (high 7.5)
- [CVE-2025-4821](https://insights.sbomify.com/CVE-2025-4821/): Incorrect congestion window growth by invalid ACK ranges (high 7.5)
- [CVE-2024-1765](https://insights.sbomify.com/CVE-2024-1765/): Unlimited resource allocation by QUIC CRYPTO frames flooding in quiche (medium 5.9)
- [CVE-2025-4820](https://insights.sbomify.com/CVE-2025-4820/): Incorrect congestion window growth by optimistic ACK (medium 5.3)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2023-6193 and fix it if it is affected.

What it is: CVE-2023-6193 is a medium-severity denial of service vulnerability in Cloudflare quiche, published on 12 Dec 2023. An attacker can exploit it over the internet without logging in, with no action from the victim.
Exploitation: There is no known exploitation of CVE-2023-6193 in the wild and no public exploit code.

Affected packages and fixed versions:
- quiche (crates.io): affected from 0.15.0; fixed in 0.19.1
- quiche (crates.io): affected from 0.15.0; fixed in 0.19.1

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-2023-6193/ (Markdown: https://insights.sbomify.com/CVE-2023-6193/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2023-6193
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2023-6193
- OSV: https://osv.dev/vulnerability/CVE-2023-6193

---
From sbomify Insights: https://insights.sbomify.com/CVE-2023-6193/
Summaries are generated and may contain mistakes; the official description above is the record.