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QNAP QTS EUVDEUVD-2025-32447

| CVE-2025-52429 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 administrator account on NAS
  2. Delivery
    Submit input with format specifiers
  3. Exploit
    Trigger CWE-134 format string flaw
  4. Execution
    Read or modify process memory
  5. Impact
    Leak secrets or corrupt memory state

Vulnerability Assessment

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

Requires a valid administrator account on the affected QNAP NAS (CVSS PR:H) - this is the primary limiting factor and excludes unauthenticated or low-privilege remote attackers. The flaw is an externally-controlled format string (CWE-134) reachable over the network (AV:N) with low complexity and no user interaction, meaning once admin access is held, exploitation is straightforward. 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. No non-default feature toggle is named in the advisory, so the condition is effectively the administrator privilege level plus a vulnerable firmware build.

Impact

This is a genuinely low-to-moderate priority issue despite the CWE-134 format string class. The vendor-supplied CVSS 4.0 vector (AV:N/AC:L/PR:H/UI:N, VC:N/VI:N/VA:L) yields only 5.1 and is dominated by the PR:H requirement - the attacker must already possess an administrator account, which drastically narrows the realistic threat population to post-authentication/insider or credential-compromise scenarios. EPSS is 0.05% (16th percentile), consistent with no public exploitation interest, and the CVE is NOT in CISA KEV and has no known POC, so exploitation status is 'no public exploit identified at time of analysis.' A notable internal conflict exists: the description states an attacker can 'obtain secret data or modify memory' (implying confidentiality and integrity impact), yet the vendor's CVSS 4.0 vector marks VC:N and VI:N and only VA:L (availability low) - the vendor's scored impact contradicts its own prose. This discrepancy should be verified with QNAP, as a format-string info-leak would normally carry at least low confidentiality impact. No SSVC decision data was provided. Overall: real but low-urgency, gated behind administrator access, with no evidence of active or opportunistic exploitation.

Exploit ScenarioDerived

An attacker who has already obtained QNAP NAS administrator credentials (via phishing, credential reuse, or prior compromise) sends crafted input containing format-string specifiers to an affected QTS/QuTS hero management function. The malformed format string is processed, allowing the attacker to read adjacent memory (leaking secret data) or write to memory. No public exploit code is known, and exploitation requires pre-existing administrative access.

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

Sensitive-data disclosure and memory modification in QNAP QTS 5.2.x and QuTS hero h5.2.x stem from an externally controlled format string (CWE-134) that is reachable over the network but requires a valid administrator account; once that prerequisite is met, an attacker can read secret data or manipulate process memory with low complexity and no user interaction. The vendor fixed the issue in QTS 5.2.6.3195 build 20250715 and QuTS hero h5.2.6.3195 build 20250715, EPSS is 0.05% (16th percentile), and no public exploit code or CISA KEV entry was identified at time of analysis.

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

RemediationAI

Upgrade to QTS 5.2.6.3195 build 20250715 or later, or QuTS hero h5.2.6.3195 build 20250715 or later, as documented in QNAP security advisory QSA-25-36 (https://www.qnap.com/en/security-advisory/qsa-25-36). No non-default feature toggle is identified in the advisory, so the practical compensating controls focus on the administrator prerequisite: restrict management-interface access to trusted networks or VPN, enforce strong authentication and MFA for all admin accounts, remove dormant or unnecessary administrator accounts, and monitor admin sessions for unexpected data access or crashes; these reduce exposure but can interrupt remote administration and require planning to avoid locking out legitimate administrators. No public exploit was identified at time of analysis, and no vendor-released workaround is specified beyond applying the fixed builds.

Affected VersionsENISA

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

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Technical ContextAI · show details

The flaw is CWE-134, a use of externally controlled format string, in QNAP's embedded Linux NAS operating systems QTS and QuTS hero. Format-string bugs occur when attacker-influenced data is passed as the format argument to printf-family functions, so format specifiers such as %s, %n, or positional tokens can cause out-of-bounds reads or writes; QNAP's advisory frames the result as secret-data exposure or memory modification. The affected firmware line is broad: CPE data enumerates QTS 5.2.0.2737 build 20240417 through 5.2.3.3006 build 20250108, and EUVD lists QTS 5.2.x before 5.2.6.3195 and QuTS hero h5.2.x before h5.2.6.3195. Network reachability (AV:N) and low attack complexity (AC:L) are offset by the high privilege requirement (PR:H) and no user interaction (UI:N); the independent CVSS:3.1 assessment scores limited confidentiality and integrity impact (C:L/I:L/A:N), while the vendor's CVSS:4.0 score is 5.1.

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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

Network-reachable management flaw (AV:N/AC:L) but requires an existing admin account (PR:H); description's 'obtain secret data or modify memory' maps to C:L/I:L, diverging from vendor's availability-only scoring.

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-2025-52429 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 common in SMB/prosumer, not everywhere
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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