CVE-2021-34359: Stored XSS Vulnerability in Proxy Server

Severity: medium (CVSS 5.4 v3.1)
Exploited in the wild: not listed in CISA KEV
EPSS: 0.6% probability of exploitation in the next 30 days
Public exploit or detection template: none known
Published: 2022-02-25 · updated 2026-06-17
Weakness: CWE-79

Description

A cross-site scripting (XSS) vulnerability has been reported to affect QNAP device running Proxy Server. If exploited, this vulnerability allows remote attackers to inject malicious code. We have already fixed this vulnerability in the following versions of Proxy Server: QTS 4.5.x: Proxy Server 1.4.2 ( 2021/12/30 ) and later

Affected products

QNAP Systems Inc. Proxy Server: before 1.4.2 — fixed in 1.4.2

How to fix

Upgrade to a fixed version: QNAP Systems Inc. Proxy Server 1.4.2. Check the vendor advisory for mitigations.

References

https://www.qnap.com/en/security-advisory/qsa-22-04
https://www.qnap.com/en/security-advisory/qsa-22-04

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