How severe is CVE-2026-41539?

CVE-2026-41539 has a CVSS score of 6.1/10, rated MEDIUM. Review your exposure and patch according to your risk tolerance.

Which products are affected by CVE-2026-41539?

Affected package information for CVE-2026-41539 is not yet fully mapped. Check the official advisory links for details.

How do I patch CVE-2026-41539?

No patch has shipped for CVE-2026-41539 yet — track the qnap qts advisory for a fixed release and apply the workarounds below in the meantime.

How do I detect CVE-2026-41539 across my infrastructure?

Inventory every qnap qts deployment and check each version against the affected-products list above. Because the exploit targets the running system rather than your application code, also watch for exploitation at the network and runtime layer — O3 flags the exploit behaviour from runtime telemetry and egress traffic even before a vulnerable build is confirmed.

How do I mitigate CVE-2026-41539 if there is no patch (or I can't update yet)?

Cut exposure now: restrict the management/admin interface to trusted networks, segment the device, and apply the vendor's recommended configuration mitigations and any WAF/IPS signature. O3's runtime protection blocks the exploit chain at execution, holding the line on unpatched or end-of-life systems until you can patch.

How does O3 Security protect against CVE-2026-41539?

O3 detects and blocks CVE-2026-41539 exploitation at runtime: eBPF exploit-chain detection, plus L7 egress monitoring that catches the post-exploitation callback and severs the attacker's outbound channel.

Is CVE-2026-41539 actively exploited in the wild?

No public exploit code has been indexed for CVE-2026-41539 yet. This does not mean the vulnerability cannot be exploited — absence of public exploits does not imply safety. Apply the recommended fix and use O3 Security to monitor your exposure.

What is the EPSS score for CVE-2026-41539?

CVE-2026-41539 has an EPSS (Exploit Prediction Scoring System) score of 0.2%, placing it in the 9th percentile of all CVEs. EPSS is maintained by FIRST.org and estimates the probability that a vulnerability will be exploited in the wild within the next 30 days. This score indicates relatively lower exploitation probability, though the CVSS severity should still guide your patching priority.

What type of vulnerability is CVE-2026-41539?

CVE-2026-41539 is classified as Cross-site Scripting (XSS) (CWE-79). This weakness type describe the underlying flaw category, which helps determine the potential impact and the right class of mitigation. This is a high-impact weakness class that often enables remote code execution or data exposure.

Which products and versions are affected by CVE-2026-41539?

CVE-2026-41539 affects qnap qts (23 versions, e.g. 5.2.0.2737, 5.2.0.2744, 5.2.0.2782…); qnap quts hero (33 versions, e.g. h5.2.0.2737, h5.2.0.2782, h5.2.0.2789…). Check the affected-products list on this page against your deployed version to confirm exposure.

When was CVE-2026-41539 published, and has it been updated?

CVE-2026-41539 was published on June 9, 2026 and was last updated on June 17, 2026. Advisory data evolves as severity scores, affected ranges, and exploit intelligence are revised — always check the latest version of the advisory before acting.

CVE-2026-41539: QTS Cross-site Scripting (XSS) (Medium 6.1)

EPSS Exploitation Probability

via FIRST.org ↗

0.2%probability of exploitation in next 30 days

Lower Risk9th percentile0.00%

EPSS (Exploit Prediction Scoring System) is a daily probability model maintained by FIRST.org. It estimates the likelihood a CVE will be exploited in production environments within the next 30 days, derived from real-world threat intelligence signals.

Description

A cross-site scripting (XSS) vulnerability has been reported to affect several QNAP operating system versions. The remote attackers can then exploit the vulnerability to bypass security mechanisms or read application data.

We have already fixed the vulnerability in the following versions: QTS 5.2.9.3492 build 20260507 and later QuTS hero h5.2.9.3499 build 20260514 and later QuTS hero h5.3.4.3500 build 20260520 and later QuTS hero h6.0.0.3500 build 20260520 and later

Affected Products

2 products · 56 configurations

OS

qtsqnap

23 versions

5.2.0.27375.2.0.27445.2.0.27825.2.0.28025.2.0.28235.2.0.28515.2.0.28605.2.1.29305.2.2.29505.2.3.30065.2.4.30705.2.4.3079

OS

quts heroqnap

33 versions

h5.2.0.2737h5.2.0.2782h5.2.0.2789h5.2.0.2802h5.2.0.2823h5.2.0.2851h5.2.0.2860h5.2.1.2929h5.2.1.2940h5.2.2.2952h5.2.3.3006h5.2.4.3070

Detection & mitigation playbook

Vendor / appliance

Detect
Inventory every qnap qts deployment and check each version against the affected-products list above. Because the exploit targets the running system rather than your application code, also watch for exploitation at the network and runtime layer — O3 flags the exploit behaviour from runtime telemetry and egress traffic even before a vulnerable build is confirmed.
Remediation status
No patch has shipped for CVE-2026-41539 yet — track the qnap qts advisory for a fixed release and apply the workarounds below in the meantime.
Mitigate without a patch
Cut exposure now: restrict the management/admin interface to trusted networks, segment the device, and apply the vendor's recommended configuration mitigations and any WAF/IPS signature. O3's runtime protection blocks the exploit chain at execution, holding the line on unpatched or end-of-life systems until you can patch.
How O3 protects you
O3 detects and blocks CVE-2026-41539 exploitation at runtime: eBPF exploit-chain detection, plus L7 egress monitoring that catches the post-exploitation callback and severs the attacker's outbound channel.

Tailored to CVE-2026-41539. Runtime protection reduces exposure until a permanent patch is applied and verified — it complements patching, it doesn't replace it.

Frequently Asked Questions

A cross-site scripting (XSS) vulnerability has been reported to affect several QNAP operating system versions. The remote attackers can then exploit the vulnerability to bypass security mechanisms or read application data. We have already fixed the vulnerability in the following versions: QTS 5.2.9.3492 build 20260507 and later QuTS hero h5.2.9.3499 build 20260514 and later QuTS hero h5.3.4.3500 build 20260520 and later QuTS hero h6.0.0.3500 build 20260520 and later

O3 Security · Runtime Protection

Is CVE-2026-41539 being exploited in your environment?

O3's eBPF runtime sensors and L7 egress monitoring detect and block the CVE-2026-41539 exploit chain at execution — protecting unpatched and end-of-life systems until the vendor patch is applied.

Protect my workloads How runtime protection works

CVE-2026-41539

EPSS Exploitation Probability

Description

Affected Products

Detection & mitigation playbook

Detect

Remediation status

Mitigate without a patch

How O3 protects you

Frequently Asked Questions

Is CVE-2026-41539 being exploited in your environment?