VulnerabilityPublished 5 Jan 2024Updated 3 Jun 2025

CVE-2023-39296: QNAP Systems QTS · Prototype Pollution

Affects QNAP Systems QTSSource CVE Database V5

Not known to be exploited · CVSS 7.5 High : upgrade to 5.2.0 soon.

Data as of 26 Oct 2026, 14:05 UTC

CVSS 3.1 base score

7.5High

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

EPSS: 1.5% chance of exploitation in 30 days – higher than 75% of CVEsExploit Prediction Scoring System: the likelihood attackers will use this flaw soon.
Patch: Available – fixed in 5.2.0

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

Attack Vector: Network
Attack Complexity: Low
Privileges Required: None
User Interaction: None
Scope: Unchanged
Confidentiality: None
Integrity: None
Availability: High

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

Attack Vector: Network: The vulnerable component is bound to the network stack and the set of possible attackers extends beyond the other options listed, 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: Specialized access conditions or extenuating circumstances do not exist. An attacker can expect repeatable success against the vulnerable component.
Privileges Required: None: The attacker is unauthorized prior to attack, and therefore does not require any access to settings or files to carry out an attack.
User Interaction: None: The vulnerable system can be exploited without any interaction from any user.
Scope: Unchanged: An exploited vulnerability can only affect resources managed by the same security authority. In this case, the vulnerable component and the impacted component are either the same, or both are managed by the same security authority.
Confidentiality: None: There is no loss of confidentiality within the impacted component.
Integrity: None: There is no loss of integrity within the impacted component.
Availability: High: There is total loss of availability, resulting in the attacker being able to fully deny access to resources in the impacted component; this loss is either sustained (while the attacker continues to deliver the attack) or persistent (the condition persists even after the attack has completed). Alternatively, the attacker has the ability to deny some availability, but the loss of availability presents a direct, serious consequence to the impacted component (e.g., the attacker cannot disrupt existing connections, but can prevent new connections; the attacker can repeatedly exploit a vulnerability that, in each instance of a successful attack, leaks a only small amount of memory, but after repeated exploitation causes a service to become completely unavailable).

Definitions: FIRST CVSS v3.1 specification.

Exploitation evidence

Disclosed: evidence found.
CVE published 5 Jan 2024
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 QNAP Systems QTS to 5.2.0.

Affected software

Product	Affected	Fixed in
QNAP Systems Inc. QTS	Affected >=5.1.0 <5.2.0	Fixed in 5.2.0

AI-suggested

European organizations should immediately verify the QTS version running on their QNAP NAS devices and upgrade to version 5.1.3.2578 build 20231110 or later, or the corresponding QuTS hero patched versions. If immediate patching is not feasible, organizations should restrict network access to QNAP management interfaces by implementing firewall rules to limit access to trusted IP addresses only, ideally isolating NAS devices from direct internet exposure. Network segmentation should be enforced to separate NAS devices from general user networks. Monitoring and logging of NAS device activity should be enhanced to detect unusual access patterns or crashes. Organizations should also review and disable any unnecessary services or remote management features on QNAP devices to reduce attack surface. Regular backups and tested recovery procedures are essential to mitigate potential downtime. Finally, organizations should stay informed on any emerging exploit reports or vendor advisories related to this vulnerability.

Description

A prototype pollution vulnerability has been reported to affect several QNAP operating system versions. If exploited, the vulnerability could allow users to override existing attributes with ones that have incompatible type, which may lead to a crash via a network. We have already fixed the vulnerability in the following versions: QTS 5.1.3.2578 build 20231110 and later QuTS hero h5.1.3.2578 build 20231110 and later

Impact

For European organizations using QNAP NAS devices running affected QTS versions, this vulnerability poses a substantial risk to service availability. QNAP NAS devices are widely used in small to medium enterprises and some larger organizations for file storage, backup, and network services. A successful exploit could cause system crashes, leading to downtime, disruption of business operations, potential data unavailability, and increased recovery costs. Although the vulnerability does not directly compromise data confidentiality or integrity, the denial-of-service impact can indirectly affect business continuity and operational resilience. Given the remote and unauthenticated nature of the exploit, attackers could target exposed QNAP devices over the internet or internal networks, especially if devices are misconfigured or lack proper network segmentation. This could be leveraged in targeted attacks or opportunistic scanning campaigns. The impact is particularly critical for organizations relying on QNAP NAS for critical storage or backup functions without immediate failover or redundancy.

CWE-1321Improperly Controlled Modification of Object Prototype Attributes ('Prototype Pollution') (opens in a new tab)
Variant weakness
The product receives input from an upstream component that specifies attributes that are to be initialized or updated in an object, but it does not properly control modifications of attributes of the object prototype.
Implementation
By freezing the object prototype first (for example, Object.freeze(Object.prototype)), modification of the prototype becomes impossible.
Architecture and Design
By blocking modifications of attributes that resolve to object prototype, such as proto or prototype, this weakness can be mitigated.
Implementation · Input Validation
When handling untrusted objects, validating using a schema can be used.
OWASP Cheat Sheets
Mass Assignment (opens in a new tab)
OWASP ASVS 4.0.3
V5.1.2 (opens in a new tab)
Attack patterns
Accessing Functionality Not Properly Constrained by ACLs (opens in a new tab)
Exploiting Incorrectly Configured Access Control Security Levels (opens in a new tab)
Manipulating User-Controlled Variables (opens in a new tab)
From MITRE CWE, MITRE CAPEC and OWASP (Top 10, OpenCRE).

References

qnap.com/en/security-advisory/qsa-23-64 (opens in a new tab)

Community reviews

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Exploitation evidence

What to do

Affected software

Description

AI analysisMachine-generated, updated 4 Jul 2025, 03:41 UTC

WeaknessesCWE-1321

Technical details

References

Community reviews

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