CVE-2025-66513VulnerabilityPublished 5 Dec 2025

CVE-2025-66513: nextcloud security-advisories · Insecure Direct Object Reference

Affects nextcloud security-advisoriesSource CVE Database V5

Not known to be exploited · CVSS 4.3 Medium · fixed in 1.0.1 : update nextcloud security-advisories when convenient.

Data as of 25 Oct 2026, 19:02 UTC

CVSS 3.1 base score

4.3Medium

How severe the flaw is on the 0–10 CVSS scale.

EPSS: 0.2% chance of exploitation in 30 days – higher than 21% of CVEsExploit Prediction Scoring System: the likelihood attackers will use this flaw soon.
Patch: Available – fixed in 1.0.1, 0.9.6, 0.8.9

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

Attack Vector: Network
Attack Complexity: Low
Privileges Required: None
User Interaction: Required
Scope: Unchanged
Confidentiality: Low
Integrity: None
Availability: None

Bold values are the worst case: easiest to exploit or largest impact.

Attack Vector: Network: The vulnerable component is bound to the network stack and the set of possible attackers extends beyond the other options listed, up to and including the entire Internet. Such a vulnerability is often termed 'remotely exploitable' and can be thought of as an attack being exploitable at the protocol level one or more network hops away (e.g., across one or more routers).
Attack Complexity: Low: Specialized access conditions or extenuating circumstances do not exist. An attacker can expect repeatable success against the vulnerable component.
Privileges Required: None: The attacker is unauthorized prior to attack, and therefore does not require any access to settings or files to carry out an attack.
User Interaction: Required: Successful exploitation of this vulnerability requires a user to take some action before the vulnerability can be exploited.
Scope: Unchanged: An exploited vulnerability can only affect resources managed by the same security authority. In this case, the vulnerable component and the impacted component are either the same, or both are managed by the same security authority.
Confidentiality: Low: There is some loss of confidentiality. Access to some restricted information is obtained, but the attacker does not have control over what information is obtained, or the amount or kind of loss is limited. The information disclosure does not cause a direct, serious loss to the impacted component.
Integrity: None: There is no loss of integrity within the impacted component.
Availability: None: There is no impact to availability within the impacted component.

Definitions: FIRST CVSS v3.1 specification.

Exploitation evidence

Disclosed: evidence found.
CVE published 5 Dec 2025
Detectable: no evidence on record.
No public nuclei template indexed
Weaponised: no evidence on record.
No public exploit code indexed in Metasploit or Exploit-DB
Exploited in the wildExploited: no evidence on record.
Not in CISA KEV and no source reports exploitation
Observed by OffSeq MirageSeen by Mirage: no evidence on record.
No attack traffic recorded by OffSeq Mirage sensors

A missing step is not evidence of safety. Sources: cve.org (opens in a new tab), the Metasploit, Exploit-DB and nuclei-templates index as of 2026-10-25.

Disclosed: The CVE record is public on cve.org. Its publication is t = 0.
Detectable: A public nuclei template can find exposed instances, for defenders and attackers alike.
Weaponised: Public exploit code exists in Metasploit or Exploit-DB, or CISA SSVC reports a public proof of concept.
Exploited in the wild: CISA KEV lists it, CISA SSVC rates exploitation active, or a source reports attacks.
Observed by OffSeq Mirage: OffSeq Mirage honeypot sensors recorded attack traffic for this CVE, or found exposed hosts without attack traffic.

Moments are spaced evenly, not to scale; a dashed line marks a gap of six months or more. Deltas count from t = 0. Sources that give only a date (CISA KEV, Exploit-DB, or a time of exactly 00:00Z) read “same day” rather than hours. Metasploit modules carry the flaw’s disclosure date, not their release date, and nuclei templates carry no date, so both appear above but not on the timeline.

What to do

Upgrade nextcloud/tables to 1.0.1, 0.9.6 or 0.8.9.

Affected software

Product	Affected	Fixed in
GitHubnextcloud/tables`pkg:github/nextcloud/tables`Other threats	Affected <0.8.9 <0.9.6 <1.0.1	Fixed in 0.8.9 0.9.6 1.0.1

Check your own hosts for these packages with threat-finder (opens in a new tab), our free open-source scanner.

AI-suggested

European organizations using Nextcloud Tables should immediately verify their version and upgrade to at least 0.8.9, 0.9.6, or 1.0.1, depending on their current version branch, to apply the official fix. Beyond patching, organizations should audit sharing permissions and metadata exposure within Nextcloud to ensure no excessive or unintended sharing exists. Implement strict access control policies and monitor user activities related to table sharing metadata access. Employ network segmentation and restrict external access to Nextcloud instances to reduce exposure. Use multi-factor authentication and strong user authentication mechanisms to limit unauthorized access. Regularly review Nextcloud security advisories and subscribe to vendor notifications for timely updates. Consider deploying Web Application Firewalls (WAFs) with rules to detect anomalous requests targeting sharing metadata endpoints. Finally, conduct user awareness training to reduce the risk of social engineering that could leverage leaked sharing information.

Description

CVE-2025-66513 is a medium severity authorization bypass vulnerability in Nextcloud Tables versions prior to 0.8.9, 0.9.6, and 1.0.1. It allows unauthorized users to access information about which tables are shared with which groups or users and their permissions, due to insufficient access control on user-controlled keys. Exploitation requires network access and some user interaction but no privileges. The vulnerability impacts confidentiality but not integrity or availability.

Impact

For European organizations, this vulnerability primarily threatens confidentiality by exposing sensitive metadata about data sharing within Nextcloud Tables. Attackers could identify which tables are shared with which users or groups, revealing organizational structure, collaboration patterns, or sensitive project information. This could facilitate targeted phishing, social engineering, or reconnaissance for more severe attacks. Although the vulnerability does not directly compromise data integrity or availability, the leakage of sharing information can undermine trust and compliance with data protection regulations such as GDPR, especially if the shared data is sensitive or regulated. Organizations relying on Nextcloud for internal collaboration and document management are at risk of unauthorized disclosure of sharing relationships, which could have reputational and operational consequences. The medium severity rating indicates moderate risk, but the ease of exploitation without privileges means organizations should prioritize patching. The lack of known exploits in the wild reduces immediate risk but does not eliminate the threat, especially as attackers may develop exploits over time.

CWE-639Authorization Bypass Through User-Controlled Key (opens in a new tab)
Base weaknessLikelihood of exploit: HighCWE Top 25 (2025): #24OWASP Top 10 A01:2025: Broken Access Control (opens in a new tab)
The system's authorization functionality does not prevent one user from gaining access to another user's data or record by modifying the key value identifying the data.
Architecture and Design
For each and every data access, ensure that the user has sufficient privilege to access the record that is being requested.
Architecture and Design · Implementation
Make sure that the key that is used in the lookup of a specific user's record is not controllable externally by the user or that any tampering can be detected.
Architecture and Design
Use encryption in order to make it more difficult to guess other legitimate values of the key or associate a digital signature with the key so that the server can verify that there has been no tampering.
OWASP Cheat Sheets
Access Control (opens in a new tab)
Authorization Testing Automation (opens in a new tab)
Cross-Site Request Forgery Prevention (opens in a new tab)
Insecure Direct Object Reference Prevention (opens in a new tab)
Authorization (opens in a new tab)
OWASP ASVS 4.0.3
V4.1.2 (opens in a new tab)
V4.2.1 (opens in a new tab)
V8.3.8 (opens in a new tab)
From MITRE CWE, MITRE CAPEC and OWASP (Top 10, OpenCRE).

References

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Exploitation evidence

What to do

Affected software

Description

AI analysisMachine-generated, updated 12 Dec 2025, 19:14 UTC

WeaknessesCWE-639

Technical details

References

Community reviews

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