VulnerabilityPublished 1 Jun 2026

CVE-2026-45155: nextcloud security-advisories · Insecure Direct Object Reference

Affects nextcloud security-advisoriesSource CVE Database V5

Compare

Not known to be exploited · CVSS 2.6 Low : upgrade to 33.0.1 or 32.0.7 when convenient.

Data as of 30 Oct 2026, 11:52 UTC

CVSS 3.1 base score

2.6Low

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

EPSS: 0.2% chance of exploitation in 30 days – higher than 9% of CVEsExploit Prediction Scoring System: the likelihood attackers will use this flaw soon.
Patch: Available – fixed in 33.0.1, 32.0.7

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

Attack Vector: Network
Attack Complexity: High
Privileges Required: Low
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: High: A successful attack depends on conditions beyond the attacker's control. That is, a successful attack cannot be accomplished at will, but requires the attacker to invest in some measurable amount of effort in preparation or execution against the vulnerable component before a successful attack can be expected. For example, a successful attack may require an attacker to: gather knowledge about the environment in which the vulnerable target/component exists; prepare the target environment to improve exploit reliability; or inject themselves into the logical network path between the target and the resource requested by the victim in order to read and/or modify network communications (e.g., a man in the middle attack).
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: 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 1 Jun 2026
Detectable: no evidence on record.
No public nuclei template indexed
Weaponized: 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 30 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.
Weaponized: A Metasploit exploit module or Exploit-DB entry exists (Metasploit scanner modules do not count), 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 security-advisories and nextcloud/server to 33.0.1 or 32.0.7.

Affected software

Product	Affected	Fixed in
nextcloudsecurity-advisories	Affected >=33.0.0 <33.0.1	Fixed in 33.0.1
nextcloudsecurity-advisories	Affected >=32.0.0 <32.0.7	Fixed in 32.0.7
GitHubnextcloud/server`pkg:github/nextcloud/server`Other threats	Affected >=32.0.0 <32.0.7 >=33.0.0 <33.0.1	Fixed in 32.0.7 33.0.1

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

AI-suggested

Upgrading Nextcloud Server to version 32.0.7 or 33.0.1 is recommended to remediate this vulnerability. For Nextcloud Enterprise Server, upgrade to versions 29.0.16.14, 30.0.17.8, 31.0.14.3, 32.0.7, or 33.0.1. No other mitigation or temporary workaround is indicated. Patch status is not explicitly stated but the vendor advisory recommends upgrading to these fixed versions.

Description

Nextcloud is an open source content collaboration platform. In Nextcloud Server from versions 32.0.0 to before 32.0.7 and 33.0.0 to before 33.0.1, a missing access check on API level allowed to add unknown circles by their ID directly to other circles. Since circle IDs have 62^15 complexity by default this is still unlikely to be executable at will, but if access to an ID was available via another source, memberships could be tracked like this. It is recommended that the Nextcloud Server is upgraded to 32.0.7 or 33.0.1. It is recommended that the Nextcloud Enterprise Server is upgraded to 29.0.16.14, 30.0.17.8, 31.0.14.3, 32.0.7 or 33.0.1

Impact

The vulnerability allows an attacker with limited privileges and user interaction to bypass authorization controls at the API level, potentially enabling them to add unknown circles to other circles. This could lead to unauthorized tracking of circle memberships. The impact on confidentiality is low, with no integrity or availability impact reported. The CVSS score of 2.6 reflects a low-severity issue requiring user interaction and high attack complexity.

Summary

CVE-2026-45155 is an authorization bypass vulnerability in Nextcloud Server's circle management API. The vulnerability arises from a missing access control check that permits adding unknown circles by their ID to other circles. Although the default circle ID complexity is high, reducing the likelihood of arbitrary exploitation, if an attacker obtains a valid circle ID through other means, they could track memberships by adding circles improperly. This affects Nextcloud Server versions 32.0.0 up to but not including 32.0.7 and 33.0.0 up to but not including 33.0.1. The issue is addressed by upgrading to 32.0.7 or 33.0.1, or the corresponding Enterprise Server versions.

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

Community reviews

Loading reviews…

Exploitation evidence

What to do

Affected software

Description

AI analysisMachine-generated, updated 1 Jun 2026, 17:20 UTC

WeaknessesCWE-639

Technical details

References

Community reviews

Related threats