Cyber Resilience

CVE-2025-66545

Nextcloud Group Folders ≤ 14.0.11

Published
05 December 2025
Modified
09 December 2025
Patch / advisory
View advisory
CVSS Score v3.1 3.5
Click a component to see what it means
Raw vectorCVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:U/C:N/I:L/A:N
EPSS Score 0.0028 20th percentile
Risk Priority 30 floored blend · peak EPSS

Summary

CVE-2025-66545 is a low-severity Improper Neutralization (CWE-707) vulnerability in Nextcloud Group Folders. Its CVSS base score is 3.5 (Low).

Operationally, exploitation aligns with the MITRE ATT&CK technique Exploit Public-Facing Application (T1190); ranked at the 20th 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 SA-11 (Developer Testing and Evaluation) and SI-10 (Information Input Validation) — see the control section below for these in your framework.

EU & UK References

Vulnerability Data

Nextcloud Groupfolders provides admin-configured folders shared by everyone in a group or team. Prior to 14.0.11, 15.3.12, 16.0.15, 17.0.14, 18.1.8, 19.1.8, and 20.1.2, a user with read-only permission can restore a file from the trash bin. This vulnerability is fixed…

more

in 14.0.11, 15.3.12, 16.0.15, 17.0.14, 18.1.8, 19.1.8, and 20.1.2.

CWE(s)
CWE-707

Related Threats

MITRE ATT&CK Enterprise Techniques

T1190 Exploit Public-Facing Application Initial Access
Adversaries may attempt to exploit a weakness in an Internet-facing host or system to initially access a network.
attack.mitre.org →
T1059 Command and Scripting Interpreter Execution
Adversaries may abuse command and script interpreters to execute commands, scripts, or binaries.
attack.mitre.org →
T1203 Exploitation for Client Execution Execution
Adversaries may exploit software vulnerabilities in client applications to execute code.
attack.mitre.org →
T1212 Exploitation for Credential Access Credential Access
Adversaries may exploit software vulnerabilities in an attempt to collect credentials.
attack.mitre.org →
Derived from this CVE’s CWE(s) via the direct CWE→ATT&CK cross-walk.

CVEs Like This One

CVE-2025-47793Same product: Nextcloud Group Folders
CVE-2025-66548Same vendor: Nextcloud
CVE-2026-4249Shared CWE-707
CVE-2025-24921Shared CWE-707
CVE-2024-43572Shared CWE-707
CVE-2025-26633Shared CWE-707
CVE-2023-46689Shared CWE-707
CVE-2025-27712Shared CWE-707
CVE-2023-42773Shared CWE-707
CVE-2025-66550Same vendor: Nextcloud

Affected Assets

nextcloud
group folders
≤ 14.0.11 · 15.0.0 — 15.3.12 · 16.0.0 — 16.0.15

Mitigating Controls

Control response

Prevent
Stop it (NIST 800-53)

—

Detect
Catch it (NIST detect / respond)

—

Harden
Shrink the surface (DISA STIG)
  • 6 hardening rules · 4 OS baselines
Validate
Prove the fix (OWASP ASVS)
  • V1.3.9

Mitigating Controls (NIST 800-53 r5) AI

SA-11 Developer Testing and Evaluation good match

Developer testing can discover missing or incorrect neutralization logic.

SI-10 Information Input Validation good match

Input validation directly enforces well-formed data and security properties before processing.

SI-15 Information Output Filtering good match

Output filtering enforces neutralization properties on data leaving the system.

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 input/output neutralization and validation to prevent malformed data handling.

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 directly require proper neutralization of inputs and outputs, eliminating CWE-707.

A.8.29 Security testing in development and acceptance mostly match
finds

Security testing can detect neutralization flaws but does not itself implement the required controls.

A.8.25 Secure development life cycle partial match
prevents

Secure development life cycle mandates input validation and output encoding that directly prevent improper neutralization.

A.8.26 Application security requirements partial match
prevents

Application security requirements explicitly call for data validation and sanitization controls addressing neutralization weaknesses.

A.8.27 Secure system architecture and engineering principles partial match
prevents

Secure architecture principles include canonicalization and safe parsing, mitigating but not fully covering neutralization issues.

Hardening callouts derived

Configuration rules from DISA STIG baselines that bear on weaknesses of the type cited by this CVE. Each rule is shown with the relationship its mapping actually records, against the CWE it was authored against. Derived via CVE→CWE over `controls_xwalks` (authoritative rows only; rows rated `none` are excluded).

Oracle Linux 9 (1 rule)
  • V-271523 OL 9 must check the GPG signature of locally installed software packages before installation. prevents CWE-707

References