Attack ChainAIDerived
Hypothetical attack flow derived from CVE metadata – not a confirmed exploit chain
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AccessObtain QNAP administrator credentials
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ExploitAuthenticate to QTS/QuTS hero over network
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ExecutionSend crafted request triggering NULL pointer dereference
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ImpactCrash service and deny storage availability
Vulnerability Assessment
| Weakness |
CWE
OWASP Top 10:2025
A10:2025 - Mishandling of Exceptional Conditions
ASVS 5.0
V16 - Security Logging and Error Handling Null pointer safety, defensive checks
MITRE ATT&CK
1 technique across 1 tactic: Impact The technique list with ATT&CK links and the kill-chain view is part of the Basic plan and up. |
| Exploitation Conditions | Exploitation requires the attacker to already possess a valid QNAP administrator account on the target device (PR:H) - this is the explicit prerequisite stated in the vendor description ('if a remote attacker gains an administrator account'). Affected products are QTS 5.2.x and QuTS hero h5.2.x builds prior to the 20250715 (build 3195) fix; devices already updated to QTS 5.2.6.3195/QuTS hero h5.2.6.3195 or later are not vulnerable. No user interaction is required (UI:N) and attack complexity is low (AC:L), but the mandatory administrator authentication is the dominant limiting factor, confining realistic exploitation to insiders or attackers who have already compromised admin credentials; impact is limited to a denial of service with no data disclosure or modification. |
| Impact | This is a genuinely low-priority issue despite a CVSS 4.0 base score of 5.1 (Medium). The signals are consistent and point to low real-world risk: the CVSS 4.0 vector (AV:N/AC:L/AT:N/PR:H/UI:N) requires high privileges - PR:H, corroborated by the description stating 'if a remote attacker gains an administrator account' - and the only impact is low availability (VA:L), i.e. a denial of service against the device's own OS with no confidentiality or integrity loss (VC:N/VI:N). EPSS is 0.14% (34th percentile), indicating very low predicted exploitation likelihood, and there is no CISA KEV listing and no public exploit code identified, so the signals do not conflict. The critical limiting factor is that an attacker must already hold a QNAP administrator account, which largely neutralizes the 'network' attack vector: an actor with admin on a NAS already has far more impactful options than crashing it, so this is best viewed as a robustness/defense-in-depth fix rather than an urgent threat. No key data is conflicting; the main caveat is that affected-version detail comes from NVD/EUVD and the vendor advisory rather than independent testing. |
| Exploit ScenarioDerived | An attacker who has already obtained QNAP administrator credentials (via phishing, credential reuse, or a prior compromise) sends a crafted request over the network to a vulnerable QTS or QuTS hero management interface, triggering a NULL pointer dereference that crashes the affected service or OS and denies storage access to legitimate users. No public proof-of-concept exploit has been identified. Because exploitation demands an existing admin account (PR:H) with low attack complexity, the barrier is credential access rather than technical difficulty. |
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Alert meAnalysisAIv2 – Oct 18, 2026
A denial-of-service condition exists in the QNAP QTS and QuTS hero NAS operating systems, where a NULL pointer dereference can be triggered by an attacker who already holds a valid administrator account on the device, crashing the affected service. Only builds prior to QTS 5.2.6.3195 build 20250715 and QuTS hero h5.2.6.3195 build 20250715 are vulnerable, and the mandatory administrative privilege (PR:H) is the dominant limiting factor, confining realistic exploitation to insiders or attackers who have already compromised admin credentials. No public exploit code has been identified at time of analysis and EPSS is low at 0.14% (34th percentile), consistent with an availability-only impact and a high-privilege prerequisite.
Earlier versions of this analysis (1)
RemediationAI
Vendor-released patch: upgrade to QTS 5.2.6.3195 build 20250715 or later, or QuTS hero h5.2.6.3195 build 20250715 or later, per QNAP advisory QSA-25-36 (https://www.qnap.com/en/security-advisory/qsa-25-36); no workaround is documented because the fix is a straightforward code-level NULL check. Where immediate upgrade is not possible, the effective compensating control is credential hygiene, since exploitation requires an existing administrator session: rotate admin passwords, remove or downgrade dormant administrator accounts, restrict administrative access to management interfaces (ports 8080/443 and the QTS web UI) to a trusted management VLAN or VPN, and enable account lockout and multi-factor authentication where the firmware supports it - the trade-off being that these measures do not remove the defect and will not help if an admin session is already hijacked. Enforce least privilege by using delegated, non-admin accounts for routine NAS operations, which limits the blast radius of credential compromise, and monitor for unexpected service restarts or crashes on the NAS as a possible indicator that the dereference has been triggered.
Affected VersionsENISA
Affects your stack
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Technical ContextAI · show details
The root cause is CWE-476, NULL pointer dereference: a code path in the QTS/QuTS hero management surface dereferences a pointer that can be NULL under attacker-influenced conditions, causing the process to fault and terminate, which manifests as a service outage rather than memory corruption or code execution. The CPE inventory confirms the vulnerable line is the QTS 5.2.0.x through 5.2.3.x release train on QNAP NAS appliances (builds 20240417 through 20250108 are enumerated), with QuTS hero h5.2.x sharing the same defect per the EUVD affected-version record. CVSS 4.0 scores this 5.1 with AV:N/AC:L/AT:N/PR:H/UI:N and a low availability-only impact (VA:L, no confidentiality or integrity effect); the independent assessment re-expresses this as CVSS:3.1/AV:N/AC:L/PR:H/UI:N/S:U/C:N/I:N/A:L, arriving at the same conclusion that the network vector and low complexity are largely neutralized by the administrator-authentication prerequisite. Because the flaw lives in trusted administrative functionality rather than a pre-auth network service, it is not remotely reachable by unauthenticated internet scanners, and there is no scope change, lateral movement, or persistence primitive implied.
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- Exploit and PoC references, threat intelligence from 22 sources
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Severity by source
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
Network-reachable management interface (AV:N) but requires an existing administrator account (PR:H); NULL deref yields only partial availability loss (A:L) with no confidentiality or integrity impact.
Primary rating from Vendor (qnapsecurity).
CVSS VectorVendor: qnapsecurity
Lifecycle Timeline
3DescriptionCVE.org
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 5.2.6.3195 build 20250715 and later QuTS hero h5.2.6.3195 build 20250715 and later
Executive ViewAI
Organizations using A NULL pointer dereference vulnerability should be aware of moderate risk from CVE-2025-52855, a null pointer dereference vulnerability rated CVSS 4.9. Exploitation could compromise the security of affected deployments. Organizations should apply vendor updates when available and monitor for exploitation.
Apply vendor patch. If patching is delayed: enable ASLR/DEP, apply network segmentation.
Threat Intelligence Overview
How this decision was reached
The engine reads each signal below and applies a fixed list of rules from top to bottom. The first rule that matches sets the recommended action – like a statement, every line is shown.
What every action level means
SSVC AssessmentENISA
Priority Score
Attack Technique
A null pointer dereference occurs when a program attempts to access memory through a pointer that has been set to NULL (address 0x0).
Denial of Service attacks render applications or systems unavailable by overwhelming resources or triggering failure conditions.
GNU Bash through 4.3 processes trailing strings after function definitions in the values of environment variables, which
GNU Bash through 4.3 bash43-025 processes trailing strings after certain malformed function definitions in the values of
QNAP QTS before 4.2.4 Build 20170313 allows attackers to execute arbitrary commands via unspecified vectors. Rated criti
QNAP QTS before 4.2.4 Build 20170313 allows attackers to gain administrator privileges and obtain sensitive information
QNAP has patched a remote code execution vulnerability affecting the QTS Media Library in all versions prior to QTS 4.2.
QNAP QTS before 4.2.4 Build 20170313 allows attackers to gain administrator privileges and execute arbitrary commands vi
QNAP QTS before 4.2.4 Build 20170313 allows local users to obtain sensitive Domain Administrator password information by
This command injection vulnerability in QTS allows attackers to run arbitrary commands in the compromised application. R
This improper input validation vulnerability allows remote attackers to inject arbitrary code to the system. Rated criti
A prototype pollution vulnerability has been reported to affect several QNAP operating system versions. Rated high sever
A buffer overflow vulnerability in external device function in QNAP QTS version 4.2.6 build 20171026, 4.3.3.0378 build 2
A buffer overflow vulnerability in password function in QNAP QTS version 4.2.6 build 20171026, 4.3.3.0378 build 20171117
EUVD-2025-32444
NVD
CVE.org
EPSS
GitHub PoC
Exploit-DB