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

Moderate severity GitHub Reviewed Published Jan 7, 2026 in quarkusio/quarkus • Updated Jan 7, 2026

Package

maven io.quarkus:quarkus-rest (Maven)

Affected versions

< 3.20.5
>= 3.21.0, < 3.27.2
>= 3.30.0, < 3.31.0

Patched versions

3.20.5
3.27.2
3.31.0

Description

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.

Workarounds

For versions without the fix applied, it is recommended to implement a health check that monitors the status and saturation of the worker thread pool. This helps detect abnormal thread retention early and allows operators to take corrective action before the application’s responsiveness is impacted.

Credits

CVE reported by Shaswata Jash, Nokia

References

@cescoffier cescoffier published to quarkusio/quarkus Jan 7, 2026
Published to the GitHub Advisory Database Jan 7, 2026
Reviewed Jan 7, 2026
Published by the National Vulnerability Database Jan 7, 2026
Last updated Jan 7, 2026

Severity

Moderate

CVSS overall score

This score calculates overall vulnerability severity from 0 to 10 and is based on the Common Vulnerability Scoring System (CVSS).
/ 10

CVSS v3 base metrics

Attack vector
Network
Attack complexity
High
Privileges required
None
User interaction
None
Scope
Unchanged
Confidentiality
None
Integrity
None
Availability
High

CVSS v3 base metrics

Attack vector: More severe the more the remote (logically and physically) an attacker can be in order to exploit the vulnerability.
Attack complexity: More severe for the least complex attacks.
Privileges required: More severe if no privileges are required.
User interaction: More severe when no user interaction is required.
Scope: More severe when a scope change occurs, e.g. one vulnerable component impacts resources in components beyond its security scope.
Confidentiality: More severe when loss of data confidentiality is highest, measuring the level of data access available to an unauthorized user.
Integrity: More severe when loss of data integrity is the highest, measuring the consequence of data modification possible by an unauthorized user.
Availability: More severe when the loss of impacted component availability is highest.
CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:H

EPSS score

Exploit Prediction Scoring System (EPSS)

This score estimates the probability of this vulnerability being exploited within the next 30 days. Data provided by FIRST.
(12th percentile)

Weaknesses

Allocation of Resources Without Limits or Throttling

The product allocates a reusable resource or group of resources on behalf of an actor without imposing any intended restrictions on the size or number of resources that can be allocated. Learn more on MITRE.

CVE ID

CVE-2025-66560

GHSA ID

GHSA-5rfx-cp42-p624

Source code

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