EUVD-2025-32476Attack ChainAIDerived
Hypothetical attack flow derived from CVE metadata – not a confirmed exploit chain
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AccessObtain valid Qsync user account
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ExploitSend crafted network request
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ExecutionTrigger NULL pointer dereference
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ImpactCrash service and deny 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 first possess a valid user account on the QNAP device running Qsync Central (PR:L / 'if a remote attacker gains a user account'), so this is not exploitable by fully unauthenticated actors. Given that precondition, no user interaction, no special non-default configuration, and no local access are needed - the attack is network-reachable (AV:N) and low-complexity (AC:L) against Qsync Central versions 4.x below 5.0.0.1. The primary limiting factor is the authentication requirement; the impact is confined to availability (service crash), with no data exposure or modification. |
| Impact | This is a moderate, authenticated denial-of-service issue rather than a high-priority threat. The CVSS 4.0 vector (CVSS:4.0/AV:N/AC:L/AT:N/PR:L/UI:N/VC:N/VI:N/VA:L) and the 5.3 score consistently point to a low-severity availability-only impact: network-reachable and low-complexity, but requiring low privileges (PR:L) - i.e. a valid user account - and producing no confidentiality or integrity loss, only partial availability impact (VA:L). All exploitation signals agree with this low ranking: EPSS is 0.15% (35th percentile), there is no CISA KEV listing, and no public exploit code has been identified. The NULL pointer dereference (CWE-476) crashes a process rather than enabling code execution. There are no conflicting signals here - the description's 'remote attacker gains a user account' precondition aligns cleanly with PR:L in the vector. The main caveat is that VA:L (rather than VA:H) suggests a limited or recoverable service disruption, so the real-world consequence is likely a degraded or crashed Qsync component rather than full device outage. This is a routine patch-management item, not an emergency. |
| Exploit ScenarioDerived | An attacker who already holds (or has obtained, e.g. via phished or weak credentials) a low-privileged user account on a QNAP device running Qsync Central sends a crafted request over the network that triggers a NULL pointer dereference, crashing the service and denying sync functionality to legitimate users. No public exploit code is known, and the low attack complexity means a working trigger would be straightforward for an authenticated actor to develop. |
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Alert meAnalysisAIv2 – Oct 18, 2026
Authenticated denial of service in Qsync Central 4.x allows a remote user with valid credentials to crash the service by triggering a NULL pointer dereference. The flaw is reachable over the network with low attack complexity, but exploitation requires an existing account on the QNAP device; impact is limited to reduced availability, with no data exposure or modification. QNAP has released a fix in Qsync Central 5.0.0.1 (2025/07/09) and later, and no public exploit was identified at time of analysis; EPSS is low at roughly 0.15%.
Earlier versions of this analysis (1)
RemediationAI
Upgrade Qsync Central to version 5.0.0.1 (2025/07/09) or later, as documented in QNAP security advisory QSA-25-34 (https://www.qnap.com/en/security-advisory/qsa-25-34); this is the vendor-released patch and resolves the NULL pointer dereference. If upgrading immediately is not possible, reduce exposure by restricting network access to the Qsync Central service to trusted network segments or VPN users, understanding that this limits legitimate sync availability for remote clients, and by enforcing least-privilege accounts and removing unused user accounts to reduce the pool of authenticated users who could trigger the crash, at the cost of additional account administration. Monitor Qsync Central service crashes and unexpected restarts as a detection signal until the patch is applied.
Affected VersionsENISA
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Technical ContextAI · show details
Qsync Central is QNAP's file synchronization service used to share and sync data across QNAP NAS devices and clients. The issue is classified as CWE-476 (NULL pointer dereference): a crafted request from an authenticated user causes the service to dereference a null pointer, leading to a crash and denial of service. The affected CPE is cpe:2.3:a:qnap:qsync_central:*:*:*:*:*:*:*:*, with EUVD scoping affected 4.x versions below 5.0.0.1 (2025/07/09). The CVSS 4.0 vector is AV:N/AC:L/AT:N/PR:L/UI:N/VC:N/VI:N/VA:L, and the independent assessment aligns with CVSS 3.1 AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:L: network-reachable, low-complexity, requiring a valid low-privileged account, with no user interaction and only a low availability impact. There is no confidentiality or integrity impact; the attacker cannot read or alter data through this flaw.
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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:L/UI:N/VC:N/VI:N/VA:L/SC:N/SI:N/SA:N
Network-reachable and low-complexity, but requires a valid user account (PR:L); NULL pointer dereference causes a service crash only, so A:L with C:N/I:N.
Primary rating from Vendor (qnapsecurity).
CVSS VectorVendor: qnapsecurity
Lifecycle Timeline
3DescriptionCVE.org
A NULL pointer dereference vulnerability has been reported to affect Qsync Central. If a remote attacker gains a user account, they can then exploit the vulnerability to launch a denial-of-service (DoS) attack.
We have already fixed the vulnerability in the following version: Qsync Central 5.0.0.1 ( 2025/07/09 ) and later
Executive ViewAI
Organizations using A NULL pointer dereference vulnerability should be aware of notable risk from CVE-2025-44011, a null pointer dereference vulnerability rated CVSS 6.5. 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
NVD
CVE.org
EPSS
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.
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GitHub PoC
Exploit-DB