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MEDIUM severity

CVE-2025-66560 — quarkus-rest

MEDIUM

CVE-2025-66560 is a medium-severity (CVSS 5.9) CWE-770 vulnerability in io.quarkus:quarkus-rest. A fix is available for io.quarkus:quarkus-rest — see the affected versions and patch details below.

Quarkus REST has potential worker thread starvation when HTTP connection is closed while waiting to write

Also known asGHSA-5rfx-cp42-p624
Published
Updated
Affected
3 pkgs
Patched
3 / 3
Exploits
None indexed
Exploitation data as of Nov 8, 2026 · OSV.dev, NVD, FIRST.org (EPSS)

Exploitation Status

No confirmed exploitation observed yet

  • CISA’s own triage has not observed active exploitation or public proof-of-concept code for this CVE as of its last assessment.

Exploitation and automatability from CISA’s SSVC triage for CVE-2025-66560.

EPSS Exploitation Probability

via FIRST.org ↗
0.4%probability of exploitation in next 30 days
Lower Risk0.00%
Lower risk than most CVEs33th percentile — riskier than 33% of all scored CVEsHighest risk
0.00%0.30%0.59%0.89%0.0%0.4%May 26Sep 26Nov 26

Probability of exploitation in the next 30 days, from FIRST.org EPSS.

How urgent is this, really

Where this sits among everything scored

Real-World Exposure

3 pkgs affected
☕io.quarkus:quarkus-rest☕io.quarkus:quarkus-rest☕io.quarkus:quarkus-rest

Real-time download stats are indexed for npm and PyPI packages. This vulnerability affects Maven packages — download data is not available via public APIs for these ecosystems.

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.

Affected Packages

3 total 3 fixed
EcosystemPackageVulnerable rangeFix
☕Mavenio.quarkus:quarkus-restall versions3.20.5io.quarkus:quarkus-rest:3.20.5
☕Mavenio.quarkus:quarkus-rest≥ 3.21.0&&< 3.27.23.27.2io.quarkus:quarkus-rest:3.27.2
☕Mavenio.quarkus:quarkus-rest≥ 3.30.0&&< 3.31.03.31.0io.quarkus:quarkus-rest:3.31.0

Affected Products

1 product · 3 configurations
Application
quarkusquarkus
≥ 3.30.0 && < 3.31.0
range

Detection & mitigation playbook

Open-source dependency

  1. Detect

    Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for io.quarkus:quarkus-rest, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.

  2. Fix

    Update io.quarkus:quarkus-rest to 3.20.5 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2025-66560 is resolved across your whole dependency graph.

  3. Workarounds

    Cap what an attacker can consume: apply request size, rate and timeout limits in front of the affected component, and run it with memory and CPU limits so exhaustion degrades one worker rather than the whole service.

Fixing This On Your OS

If you run this on a Linux distribution, patch through your package manager against the distro's own security advisory below — it tracks the exact backported fix for your release, which can ship on a different timeline (and sometimes a different severity) than the upstream project.

Red HatModerate

This vulnerability is rated Moderate for Red Hat products utilizing Quarkus REST, including Red Hat AMQ, Cryostat, Enterprise Application Platform, OpenShift Container Platform, and Red Hat Build of Quarkus. The flaw in the HTTP layer can lead to an application-level denial of service if remote attackers repeatedly…

Workaround published by Red Hat
Mitigation for this issue is either not available or the currently available options do not meet the Red Hat Product Security criteria comprising ease of use and deployment, applicability to widespread installation base or stability.
Source: Red Hat security advisory for CVE-2025-66560 (CC BY 4.0)
ProductFixed inAdvisory
Red Hat build of Quarkus 3.20.5.redhatio.quarkus/quarkus-rest:3.20.5.redhat-00001RHSA-2026:1899
Red Hat build of Quarkus 3.27.2.redhatio.quarkus/quarkus-rest:3.27.2.redhat-00001RHSA-2026:1965

Frequently Asked Questions

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
O3 Security · Impact-Aware SCA

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CVE-2025-66560: quarkus-rest — Fixed in 3.20.5