CVE-2025-66549

Info Disclosure in Nextcloud Desktop 3.0.0 – 3.16.5

Info Disclosure

Published

05 December 2025

Modified

09 December 2025

Patch / advisory

View advisory

CVSS Score v3.1 2.4

Click a component to see what it means

Raw vector

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

EPSS Score 0.0029 21th percentile

Risk Priority 23 floored blend · peak EPSS

Summary

CVE-2025-66549 is a low-severity Generation of Error Message Containing Sensitive Information (CWE-209) vulnerability in Nextcloud Desktop. Its CVSS base score is 2.4 (Low).

Operationally, exploitation aligns with the MITRE ATT&CK technique Software (T1592.002); ranked at the 21th percentile by exploit likelihood (below the median); it is not currently listed in the CISA KEV catalog.

The strongest mitigations our analysis identified map to SI-11 (Error Handling) — see the control section below for these in your framework.

OWASP Top 10 for Web (2025)

EU & UK References

🇪🇺 ENISA EUVD: EUVD-2025-201462

Vulnerability Data

Nextcloud Desktop is the desktop sync client for Nextcloud. Prior to 3.16.5, when trying to manually lock a file inside an end-to-end encrypted directory, the path of the file was sent to the server unencrypted, making it possible for administrators…

to see it in log files. This vulnerability is fixed in 3.16.5.

CWE(s): CWE-209

Related Threats

MITRE ATT&CK Enterprise Techniques

T1592.002 Software Reconnaissance

Adversaries may gather information about the victim's host software that can be used during targeting.

attack.mitre.org →

T1082 System Information Discovery Discovery

An adversary may attempt to get detailed information about the operating system and hardware, including version, patches, hotfixes, service packs, and architecture.

attack.mitre.org →

T1592 Gather Victim Host Information Reconnaissance

Adversaries may gather information about the victim's hosts that can be used during targeting.

attack.mitre.org →

T1595 Active Scanning Reconnaissance

Adversaries may execute active reconnaissance scans to gather information that can be used during targeting.

attack.mitre.org →

Derived from this CVE’s CWE(s) via the direct CWE→ATT&CK cross-walk.

CVEs Like This One

CVE-2023-23942Same product: Nextcloud Desktop

CVE-2023-28998Same product: Nextcloud Desktop

CVE-2024-52510Same product: Nextcloud Desktop

CVE-2023-29000Same product: Nextcloud Desktop

CVE-2023-22472Same product: Nextcloud Desktop

CVE-2023-28997Same product: Nextcloud Desktop

CVE-2025-47792Same product: Nextcloud Desktop

CVE-2023-28999Same product: Nextcloud Desktop

CVE-2023-34339Shared CWE-209

CVE-2025-0279Shared CWE-209

Affected Assets

nextcloud

desktop

3.0.0 — 3.16.5

Mitigating Controls

Control response

Prevent

Stop it (NIST 800-53)

—

Detect

Catch it (NIST detect / respond)

—

Harden

Shrink the surface (DISA STIG)

—

Validate

Prove the fix (OWASP ASVS)

V16.5.1

Mitigating Controls (NIST 800-53 r5) AI

SI-11 Error Handling good match

si-11 directly requires error messages to avoid revealing exploitable information about the system or its data.

Mitigating Controls (NIST CSF 2.0) AI

Derived directly from the weakness types (CWEs) cited in the NVD entry via our AI-authored CWE→CSF cross-walk (authority under review) — links open the control.

PR.PS-06 mostly match

prevents

Secure SDLC practices directly require sanitized error handling to prevent sensitive data disclosure.

Mitigating Controls (ISO/IEC 27001:2022 Annex A) AI

Derived directly from the weakness types (CWEs) cited in the NVD entry via our AI-authored CWE→ISO cross-walk (authority under review) — links open the control.

A.8.28 Secure coding mostly match

prevents

Secure coding standards explicitly forbid exposing sensitive data in errors.

A.8.29 Security testing in development and acceptance mostly match

finds

Security testing can detect error messages that leak sensitive information.

A.8.15 Logging partial match

degrades

Logging policy can require suppression of sensitive data in error messages.

A.8.25 Secure development life cycle partial match

prevents

Secure SDLC mandates error-handling rules that avoid leaking sensitive information.