CVE-2026-23721VulnerabilityPublished 19 Jan 2026

CVE-2026-23721: opf openproject · Missing Authorization

Affects opf openprojectSource CVE Database V5

Not known to be exploited · CVSS 4.3 Medium : upgrade to 16.6.5 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 10% of CVEsExploit Prediction Scoring System: the likelihood attackers will use this flaw soon.
Patch: Available – fixed in 16.6.5

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 19 Jan 2026
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 openproject and opf/openproject to 16.6.5.

Affected software

Product	Affected	Fixed in
opfopenproject	Affected <16.6.5 =17.0.0	Fixed in 16.6.5
GitHubopf/openproject`pkg:github/opf/openproject`Other threats	Affected <16.6.5 =17.0.0	Fixed in 16.6.5

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 upgrade OpenProject installations to version 16.6.5 or 17.0.1 or later, where the vulnerability is fixed. Until upgrades are applied, organizations should audit user permissions to minimize the number of users granted 'View Members' permission, restricting it only to those who absolutely require it. Implement strict access controls and monitor for unusual access patterns to group membership data. Employ multi-factor authentication (MFA) to reduce the risk of account compromise that could lead to exploitation. Regularly review and update group memberships and permissions to ensure least privilege principles are enforced. Additionally, consider network segmentation and application-layer firewalls to limit access to OpenProject instances. Maintain up-to-date logging and alerting to detect any attempts to enumerate groups or access sensitive user information. Since no workarounds exist, patching remains the most effective mitigation.

Description

CVE-2026-23721 is a medium severity vulnerability in OpenProject, an open-source project management tool. The flaw involves missing authorization checks allowing users with 'View Members' permission in any project to enumerate all groups and see their members, even if they shouldn't have access. This issue affects OpenProject versions prior to 16.6.5 and version 17.0.0, and has been fixed in versions 16.6.5 and 17.0.

Impact

For European organizations, the primary impact of CVE-2026-23721 is the unauthorized disclosure of user group membership information within OpenProject. This could lead to increased risk of targeted social engineering or spear-phishing attacks by revealing internal team structures and user roles. While the vulnerability does not allow data modification or system disruption, the leakage of membership data can compromise confidentiality and potentially aid attackers in reconnaissance phases of an attack. Organizations with strict data privacy requirements, such as those governed by GDPR, may face compliance risks if sensitive user information is exposed. The impact is more pronounced in organizations where OpenProject is used extensively for managing sensitive projects or where group membership reflects sensitive organizational hierarchies. Since exploitation requires authenticated access with 'View Members' permission, the risk is limited to insiders or compromised accounts but remains significant in environments with many users having this permission. The absence of known exploits reduces immediate risk but does not eliminate the need for prompt remediation.

CWE-862Missing Authorization (opens in a new tab)
Class weaknessLikelihood of exploit: HighCWE Top 25 (2025): #4OWASP Top 10 A01:2025: Broken Access Control (opens in a new tab)
The product does not perform an authorization check when an actor attempts to access a resource or perform an action.
Architecture and Design
Divide the product into anonymous, normal, privileged, and administrative areas. Reduce the attack surface by carefully mapping roles with data and functionality. Use role-based access control (RBAC) to enforce the roles at the appropriate boundaries.
Architecture and Design
Ensure that access control checks are performed related to the business logic. These checks may be different than the access control checks that are applied to more generic resources such as files, connections, processes, memory, and database records.
Architecture and Design · Libraries or Frameworks
Use a vetted library or framework that does not allow this weakness to occur or provides constructs that make this weakness easier to avoid.
OWASP Cheat Sheets
Authorization (opens in a new tab)
OWASP ASVS 4.0.3
V8.3.8 (opens in a new tab)
V13.4.2 (opens in a new tab)
V7.2.2 (opens in a new tab)
Attack patterns
Exploitation of Thunderbolt Protection Flaws (opens in a new tab)
From MITRE CWE, MITRE CAPEC and OWASP (Top 10, OpenCRE).

References

github.com/opf/openproject/security/advisories/GHSA-vj77-wrc2-5h5h (opens in a new tab)

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Exploitation evidence

What to do

Affected software

Description

AI analysisMachine-generated, updated 26 Jan 2026, 20:11 UTC

WeaknessesCWE-862

Technical details

References

Community reviews

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