VulnerabilityPublished 2 Jan 2026Updated 5 Jan 2026

CVE-2025-53596: QNAP Systems QTS · NULL Pointer Dereference

Affects QNAP Systems QTSSource CVE Database V5

Not known to be exploited · CVSS 1.2 Low : upgrade to 5.2.7.3256 build 20250913 when convenient.

Data as of 26 Oct 2026, 14:05 UTC

CVSS 4.0 base score

1.2Low

How severe the flaw is on the 0–10 CVSS scale.

EPSS: 0.3% chance of exploitation in 30 days – higher than 29% of CVEsExploit Prediction Scoring System: the likelihood attackers will use this flaw soon.
Patch: Available – fixed in 5.2.7.3256 build 20250913, h5.3.1.3250 build 20250912, h5.2.7.3256 build 20250913

CVSS:4.0/AV:N/AC:L/AT:N/PR:H/UI:N/VC:N/VI:N/VA:L/SC:N/SI:N/SA:N/E:U

Base metrics

Attack Vector: Network
Attack Complexity: Low
Attack Requirements: None
Privileges Required: High
User Interaction: None
Vulnerable system confidentiality: None
Vulnerable system integrity: None
Vulnerable system availability: Low
Subsequent system confidentiality: None
Subsequent system integrity: None
Subsequent system availability: None

Threat metrics

Exploit Maturity: Unreported

Bold values are the worst case: easiest to exploit or largest impact.

Attack Vector: Network: The vulnerable system is bound to the network stack and the set of possible attackers extends beyond the other options listed below, up to and including the entire Internet. Such a vulnerability is often termed “remotely exploitable” and can be thought of as an attack being exploitable at the protocol level one or more network hops away (e.g., across one or more routers).
Attack Complexity: Low: The attacker must take no measurable action to exploit the vulnerability. The attack requires no target-specific circumvention to exploit the vulnerability. An attacker can expect repeatable success against the vulnerable system.
Attack Requirements: None: The successful attack does not depend on the deployment and execution conditions of the vulnerable system. The attacker can expect to be able to reach the vulnerability and execute the exploit under all or most instances of the vulnerability.
Privileges Required: High: The attacker requires privileges that provide significant (e.g., administrative) control over the vulnerable system allowing full access to the vulnerable system’s settings and files.
User Interaction: None: The vulnerable system can be exploited without interaction from any human user, other than the attacker.
Vulnerable system confidentiality: None: There is no loss of confidentiality within the Vulnerable System.
Vulnerable system integrity: None: There is no loss of integrity within the Vulnerable System.
Vulnerable system availability: Low: Performance is reduced or there are interruptions in resource availability. Even if repeated exploitation of the vulnerability is possible, the attacker does not have the ability to completely deny service to legitimate users. The resources in the Vulnerable System are either partially available all of the time, or fully available only some of the time, but overall there is no direct, serious consequence to the Vulnerable System.
Subsequent system confidentiality: None: There is no loss of confidentiality within the Subsequent System or all confidentiality impact is constrained to the Vulnerable System.
Subsequent system integrity: None: There is no loss of integrity within the Subsequent System or all integrity impact is constrained to the Vulnerable System.
Subsequent system availability: None: There is no impact to availability within the Subsequent System or all availability impact is constrained to the Vulnerable System.
Exploit Maturity: Unreported: Based on threat intelligence sources each of the following must apply: · No knowledge of publicly available proof-of-concept · No knowledge of reported attempts to exploit this vulnerability · No knowledge of publicly available solutions used to simplify attempts to exploit the vulnerability

Definitions: FIRST CVSS v4.0 specification.

Exploitation evidence

Disclosed: evidence found.
CVE published 2 Jan 2026
Detectable: no evidence on record.
No public nuclei template indexed
Weaponised: no evidence on record.
No public exploit code indexed in Metasploit or Exploit-DB
Exploited in the wildExploited: no evidence on record.
Not in CISA KEV and no source reports exploitation
Observed by OffSeq MirageSeen by Mirage: no evidence on record.
No attack traffic recorded by OffSeq Mirage sensors

A missing step is not evidence of safety. Sources: cve.org (opens in a new tab), the Metasploit, Exploit-DB and nuclei-templates index as of 26 Oct 2026.

Disclosed: The CVE record is public on cve.org. Its publication is t = 0.
Detectable: A public nuclei template can find exposed instances, for defenders and attackers alike.
Weaponised: Public exploit code exists in Metasploit or Exploit-DB, or CISA SSVC or the CVSS exploit maturity reports a public proof of concept.
Exploited in the wild: CISA KEV lists it, CISA SSVC rates exploitation active, or a source reports attacks.
Observed by OffSeq Mirage: OffSeq Mirage honeypot sensors recorded attack traffic for this CVE, or found exposed hosts without attack traffic.

Moments are spaced evenly, not to scale; a dashed line marks a gap of six months or more. Deltas count from t = 0. Sources that give only a date (CISA KEV, Exploit-DB, or a time of exactly 00:00Z) read “same day” rather than hours. Metasploit modules carry the flaw’s disclosure date, not their release date, and nuclei templates carry no date, so both appear above but not on the timeline.

What to do

Upgrade QTS to 5.2.7.3256 build 20250913; QuTS hero to h5.3.1.3250 build 20250912 or h5.2.7.3256 build 20250913.

Affected software

Product	Affected	Fixed in
QNAP Systems Inc.QTS	Affected =>=5.2.0 <5.3.0	Fixed in 5.2.7.3256 build 20250913
QNAP Systems Inc.QuTS hero	Affected ≥ h5.2.x, < h5.2.7.3256 build 20250913 ≥ h5.3.x, < h5.3.1.3250 build 20250912	Fixed in h5.3.1.3250 build 20250912 h5.2.7.3256 build 20250913

AI-suggested

European organizations should immediately verify the QTS version running on their QNAP NAS devices and upgrade to the patched versions: QTS 5.2.7.3256 build 20250913 or later, QuTS hero h5.2.7.3256 build 20250913 or later, or QuTS hero h5.3.1.3250 build 20250912 or later. Restrict administrator access to trusted personnel and enforce strong authentication mechanisms, such as multi-factor authentication (MFA), to reduce the risk of credential compromise. Disable remote administration if not required or restrict it via VPN or IP whitelisting to limit exposure. Regularly audit administrator accounts and monitor logs for suspicious activity indicating potential misuse. Implement network segmentation to isolate NAS devices from general user networks, minimizing lateral movement opportunities. Maintain up-to-date backups to ensure rapid recovery in case of DoS-induced outages. Finally, stay informed on QNAP security advisories and apply security patches promptly to mitigate emerging threats.

Description

A NULL pointer dereference vulnerability has been reported to affect several QNAP operating system versions. If a remote attacker gains an administrator account, they can then exploit the vulnerability to launch a denial-of-service (DoS) attack. We have already fixed the vulnerability in the following versions: QTS 5.2.7.3256 build 20250913 and later QuTS hero h5.2.7.3256 build 20250913 and later QuTS hero h5.3.1.3250 build 20250912 and later

Impact

For European organizations, the primary impact of CVE-2025-53596 is a denial-of-service condition on QNAP NAS devices running vulnerable QTS versions. This can disrupt critical data storage services, backup operations, and file sharing, potentially causing operational downtime. Organizations relying heavily on QNAP NAS for business continuity, especially in sectors like finance, healthcare, and government, may experience service interruptions. However, since exploitation requires administrator access, the risk of widespread compromise is limited unless internal credentials are compromised. The vulnerability does not allow data theft or system takeover, so confidentiality and integrity impacts are minimal. Still, availability disruptions can affect productivity and incident response capabilities. European entities with remote administration enabled on QNAP devices are at higher risk, as attackers with stolen credentials could trigger DoS attacks remotely. The absence of known exploits reduces immediate threat but does not eliminate the risk of future exploitation.

CWE-476NULL Pointer Dereference (opens in a new tab)
Base weaknessLikelihood of exploit: MediumCWE Top 25 (2025): #13OWASP Top 10 A10:2025: Mishandling of Exceptional Conditions (opens in a new tab)
The product dereferences a pointer that it expects to be valid but is NULL.
Implementation
For any pointers that could have been modified or provided from a function that can return NULL, check the pointer for NULL before use. When working with a multithreaded or otherwise asynchronous environment, ensure that proper locking APIs are used to lock before the check, and unlock when it has finished.
Requirements
Select a programming language that is not susceptible to these issues.
Implementation
Check the results of all functions that return a value and verify that the value is non-null before acting upon it.
OWASP Cheat Sheets
Logging (opens in a new tab)
Error Handling (opens in a new tab)
OWASP ASVS 4.0.3
V11.1.7 (opens in a new tab)
From MITRE CWE, MITRE CAPEC and OWASP (Top 10, OpenCRE).

References

qnap.com/en/security-advisory/qsa-25-50 (opens in a new tab)

Community reviews

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Exploitation evidence

What to do

Affected software

Description

AI analysisMachine-generated, updated 9 Jan 2026, 17:02 UTC

WeaknessesCWE-476

Technical details

References

Community reviews

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