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QNAP QTS EUVDEUVD-2025-32465

| CVE-2025-48730 MEDIUM
Use of Externally-Controlled Format String (CWE-134)
2025-10-03 security@qnapsecurity.com.tw
5.1
CVSS 4.0 · Vendor: qnapsecurity
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Attack ChainAIDerived

Hypothetical attack flow derived from CVE metadata – not a confirmed exploit chain

  1. Access
    Obtain QNAP administrator account
  2. Exploit
    Submit crafted format-string input to admin function
  3. Execution
    Trigger CWE-134 format string processing
  4. Impact
    Leak memory secrets or corrupt memory

Vulnerability Assessment

Weakness
CWE
OWASP Top 10:2025
A05:2025 - Injection
ASVS 5.0
V1 - Encoding and Sanitization Format string safety
Exploitation Conditions

Exploitation requires the attacker to already possess a QNAP operating-system administrator account (reflected in CVSS PR:H) - there is no unauthenticated path. Affected deployments are QTS 5.2.x prior to 5.2.6.3195 build 20250715 and QuTS hero h5.2.x prior to h5.2.6.3195 build 20250715; patched builds are not exploitable. The decisive limiting factor is the administrator-credential prerequisite, which confines realistic exploitation to insiders, credential-theft follow-on, or already-compromised admin sessions rather than opportunistic remote attack.

Impact

This is a genuine but low-priority issue. The vendor-supplied CVSS 4.0 vector (AV:N/AC:L/AT:N/PR:H/UI:N) and base score of 5.1 (Medium) hinge entirely on PR:H - exploitation requires the attacker to already hold a QNAP administrator account, which is explicitly confirmed by the description ('If a remote attacker gains an administrator account'). All exploitation-likelihood signals point low: EPSS is 0.05% (16th percentile), the CVE is NOT on CISA KEV, and no public exploit code is identified in the provided data - so this is 'no public exploit identified at time of analysis.' There is a notable internal conflict in the impact metrics: the description states the attacker can 'obtain secret data or modify memory' (implying confidentiality and integrity impact), yet the vendor 4.0 vector sets VC:N/VI:N and only VA:L (availability-low) - verify the true impact breakdown with QNAP's QSA-25-36 advisory, as the stated effects and scored metrics disagree. No SSVC decision data was supplied. Net: a high-privilege, low-probability, medium-severity bug - patch in routine cycles rather than as an emergency, since the admin-account prerequisite makes an unauthenticated internet-wide attack impossible.

Exploit ScenarioDerived

An attacker who has already compromised or been granted a QNAP NAS administrator account sends crafted input containing format-string specifiers to an affected administrative function, causing the process to leak memory contents (secret data) or corrupt memory. No public exploit code is identified, and the network attack vector is gated entirely behind the required admin privileges, so this is a post-authentication escalation/disclosure primitive rather than an initial-access vector.

This Month Plan within 30 days. Why: MEDIUM severity (CVSS 4.0-6.9).
Patch available 0.1% exploitation probability (EPSS)

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AnalysisAIv2 – Oct 18, 2026

Authenticated administrators on QNAP QTS and QuTS hero can exploit externally controlled format strings to disclose secret data or corrupt memory, but only after obtaining an existing administrator account. QTS 5.2.x before 5.2.6.3195 build 20250715 and QuTS hero h5.2.x before h5.2.6.3195 build 20250715 are affected; patched builds are not exploitable. EPSS is low at 0.05% (16th percentile) and no public exploit identified at time of analysis.

Earlier versions of this analysis (1)
v1 Mar 13, 2026 - 19:29 CVSS 6.5

RemediationAI

Upgrade QTS to 5.2.6.3195 build 20250715 or later, and QuTS hero to h5.2.6.3195 build 20250715 or later; the vendor advisory is https://www.qnap.com/en/security-advisory/qsa-25-36. Because exploitation requires an administrator account, the main compensating controls are to remove unnecessary admin accounts, enforce MFA for all administrative logins, and alert on anomalous admin sessions; the trade-off is added login friction and possible client-compatibility work. Restrict the QNAP management interface to trusted management VLANs or source IPs and disable remote administration where not required; this reduces attack surface but can complicate remote support. Monitor logs for unexpected format-string errors or admin-console abuse.

Affected VersionsENISA

QTS 5.2.x <5.2.6.3195 build 20250715
QuTS hero h5.2.x <h5.2.6.3195 build 20250715

Affects your stack

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Checking this CVE against your own stacks and servers is part of the Basic plan and up.

Technical ContextAI · show details

CWE-134 (use of externally-controlled format string) occurs when an application passes attacker-influenced data as the format argument to a printf-style function rather than as a value, allowing format specifiers such as %n to drive unintended memory reads or writes. In QNAP QTS and QuTS hero NAS operating systems, the flaw is reachable only with administrator credentials (CVSS PR:H), making it a post-authentication issue rather than a remote unauthenticated primitive. The CPE data maps affected QTS builds from 5.2.0.2737 through 5.2.3.3006, while EUVD identifies QTS 5.2.x before 5.2.6.3195 build 20250715 and QuTS hero h5.2.x before h5.2.6.3195 build 20250715 as the vulnerable ranges; the 5.2.6.3195 build is the vendor fix.

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Severity by source

Vendor (qnapsecurity) PRIMARY 5.1 MEDIUM
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
vuln.today AI 3.8 LOW

Admin account required so PR:H; network-reachable admin interface and no user interaction give AV:N/AC:L/UI:N; description's 'secret data' and 'modify memory' justify C:L/I:L.

3.1 AV:N/AC:L/PR:H/UI:N/S:U/C:L/I:L/A:N
4.0 AV:N/AC:L/AT:N/PR:H/UI:N/VC:L/VI:L/VA:N/SC:N/SI:N/SA:N

Primary rating from Vendor (qnapsecurity).

CVSS VectorVendor: qnapsecurity

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

Lifecycle Timeline

3
CVSS changed
Oct 18, 2026 - 21:38 NVD
6.5 (MEDIUM) 5.1 (MEDIUM)
Patch available
Apr 16, 2026 - 05:29 EUVD
5.2.6.3195
CVE Published
Oct 03, 2025 - 19:15 nvd
MEDIUM 6.5

DescriptionCVE.org

A use of externally-controlled format string 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 obtain secret data or modify memory.

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

Why It Matters

Organizations using A use of externally-controlled format string vulnerability should be aware of notable risk from CVE-2025-48730 rated CVSS 6.5. Exploitation could compromise the security of affected deployments. Organizations should apply vendor updates when available and monitor for exploitation.

Business Impact: Moderate
Compensating Controls

Apply vendor patch. If patching is delayed: restrict network access and enable monitoring.

Threat Intelligence Overview

EPSS Score
0.1%
Top 84% exploitable
Prevalence
Medium
QNAP QTS/QuTS hero NAS appliances common in SMB and prosumer, not ubiquitous
Data Quality
4 sources
Confidence: Medium

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.

SignalValue
Severity MEDIUM
CISA KEV No
Public POC No
EPSS 0.1%
Patch available Yes
Active threat No
Deciding rule
MEDIUM severity (CVSS 4.0-6.9)
What every action level means
Emergency Immediate action required. Criteria: CRITICAL + in CISA KEV (actively exploited) without patch, OR CRITICAL + EPSS > 30% without patch, OR CRITICAL + active threat signals without patch.
Act Now Prioritize within 24-48h. Criteria: in KEV with patch available, OR CRITICAL + public POC, OR HIGH + EPSS > 10%, OR CRITICAL + active threat, OR any CRITICAL severity.
This Week Schedule remediation this week. Criteria: HIGH severity (CVSS 7.0-8.9). Patch within normal change window.
This Month Plan within 30 days. Criteria: MEDIUM severity (CVSS 4.0-6.9), lower exploitation probability. Include in regular patch cycle.
Monitor Track and reassess. Criteria: LOW severity (CVSS 0.1-3.9), minimal exploitation risk. No immediate action needed.

SSVC AssessmentENISA

Exploitation· derived
None
System Exposure· derived
Open
Automatable· derived
No

Priority Score

26
Low Medium High Critical
KEV: 0
EPSS: 0
CVSS: +26
PoC: 0
Weaponized: 0
Threat intel: 0
Gov advisory: 0

Attack Technique

Information disclosure occurs when an application unintentionally exposes sensitive data that aids attackers in reconnaissance or directly compromises security.

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