CVE-2021-34357: Reflected XSS Vulnerability in QmailAgent

Severity: medium (CVSS 6.1 v3.1)
Exploited in the wild: not listed in CISA KEV
EPSS: 0.7% probability of exploitation in the next 30 days
Public exploit or detection template: none known
Published: 2021-11-13 · updated 2026-06-17
Weakness: CWE-79

Description

A cross-site scripting (XSS) vulnerability has been reported to affect QNAP device running QmailAgent. If exploited, this vulnerability allows remote attackers to inject malicious code. We have already fixed this vulnerability in the following versions of QmailAgent: QmailAgent 3.0.2 ( 2021/08/25 ) and later

Affected products

QNAP Systems Inc. QmailAgent: before 3.0.2 — fixed in 3.0.2

How to fix

Upgrade to a fixed version: QNAP Systems Inc. QmailAgent 3.0.2. Check the vendor advisory for mitigations.

References

https://www.qnap.com/en/security-advisory/qsa-21-47
https://www.qnap.com/en/security-advisory/qsa-21-47

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