VulnerabilityPublished 5 Dec 2025

CVE-2025-66553: nextcloud security-advisories · Insecure Direct Object Reference

Affects nextcloud security-advisoriesSource CVE Database V5

Not known to be exploited · CVSS 4.3 Medium : upgrade to 0.8.7 when convenient.

Data as of 26 Oct 2026, 15:59 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 19% of CVEsExploit Prediction Scoring System: the likelihood attackers will use this flaw soon.
Patch: Available – fixed in 0.8.7

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

Attack Vector: Network
Attack Complexity: Low
Privileges Required: Low
User Interaction: None
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: Low: The attacker is authorized with (i.e., requires) privileges that provide basic user capabilities that could normally affect only settings and files owned by a user. Alternatively, an attacker with Low privileges may have the ability to cause an impact only to non-sensitive resources.
User Interaction: None: The vulnerable system can be exploited without any interaction from any user.
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 26 Oct 2026.

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 or the CVSS exploit maturity 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 0.8.7.

Affected software

Product	Affected	Fixed in
GitHubnextcloud/tables`pkg:github/nextcloud/tables`Other threats	Affected <0.8.7	Fixed in 0.8.7

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

AI-suggested

European organizations should immediately identify Nextcloud Tables deployments running affected versions (<0.8.7 or >=0.9.0-beta.1 and <0.9.4) and upgrade to versions 0.8.7 or 0.9.4 or later where the vulnerability is fixed. In addition to patching, organizations should audit user permissions and access controls within Nextcloud to ensure that only authorized users have access to the Tables app and its metadata. Implement strict authentication and session management policies to reduce the risk of compromised accounts being used to exploit this flaw. Network segmentation and monitoring of Nextcloud API requests can help detect anomalous access patterns involving numeric ID manipulation. Security teams should also review logs for unusual access to metadata endpoints and consider deploying Web Application Firewalls (WAFs) with rules to block suspicious parameter tampering. Finally, raising user awareness about the importance of credential security will help mitigate risks from insider threats or account compromise.

Description

CVE-2025-66553 is a medium-severity authorization bypass vulnerability in Nextcloud Tables versions prior to 0.8.7 and between 0.9.0-beta.1 and 0.9.4. Authenticated users could manipulate numeric IDs in requests to view metadata of columns in other users' tables, exposing potentially sensitive schema information. This vulnerability does not allow modification or deletion of data, nor does it require user interaction beyond authentication.

Impact

For European organizations, this vulnerability could lead to unauthorized disclosure of metadata about table structures within Nextcloud Tables, potentially revealing organizational data schemas or sensitive configuration details. While the direct confidentiality impact is limited to metadata and does not expose actual user data or allow data modification, such information could aid attackers in reconnaissance or facilitate further targeted attacks. Organizations in sectors with strict data privacy regulations (e.g., GDPR) may face compliance risks if unauthorized metadata disclosure is considered sensitive. The vulnerability requires authenticated access, so insider threats or compromised accounts pose the main risk vector. Given Nextcloud's widespread adoption in European public administrations, educational institutions, and enterprises, especially in Germany, France, the Netherlands, and the Nordics, the impact could be significant in these regions. However, the absence of known exploits and the medium severity rating suggest a moderate risk level if promptly mitigated.

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, 19:15 UTC

WeaknessesCWE-639

Technical details

References

Community reviews

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