CVE-2026-23646VulnerabilityPublished 19 Jan 2026

CVE-2026-23646: opf openproject · Exposure of Data Element to Wrong Session

Affects opf openprojectSource CVE Database V5

Not known to be exploited · CVSS 6.5 Medium : upgrade to 16.6.5 when convenient.

Data as of 25 Oct 2026, 19:02 UTC

CVSS 3.1 base score

6.5Medium

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

EPSS: 0.3% chance of exploitation in 30 days – higher than 31% 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:N/I:N/A:H

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

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: None: There is no loss of confidentiality within the impacted component.
Integrity: None: There is no loss of integrity within the impacted component.
Availability: High: There is total loss of availability, resulting in the attacker being able to fully deny access to resources in the impacted component; this loss is either sustained (while the attacker continues to deliver the attack) or persistent (the condition persists even after the attack has completed). Alternatively, the attacker has the ability to deny some availability, but the loss of availability presents a direct, serious consequence to the impacted component (e.g., the attacker cannot disrupt existing connections, but can prevent new connections; the attacker can repeatedly exploit a vulnerability that, in each instance of a successful attack, leaks a only small amount of memory, but after repeated exploitation causes a service to become completely unavailable).

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

The primary and only effective mitigation is to upgrade OpenProject installations to version 16.6.5 or 17.0.1 or later, where the session ownership verification flaw is fixed. Organizations should audit their OpenProject versions and prioritize patching vulnerable instances. If immediate patching is not feasible, restricting access to the OpenProject web interface via network controls such as VPNs, IP whitelisting, or web application firewalls can reduce exposure. Monitoring web server logs for unusual DELETE requests to the sessions endpoint may help detect exploitation attempts. Additionally, implementing multi-factor authentication and session timeout policies can reduce the window of opportunity for attackers. Regular backups and incident response plans should be in place to quickly recover from any disruption caused by forced logouts.

Description

CVE-2026-23646 is a medium-severity vulnerability in OpenProject versions prior to 16.6.5 and version 17.0.0, where users can delete other users' active sessions due to improper session ownership validation. This allows an attacker to unauthenticate other users by iterating session IDs in DELETE requests without needing elevated permissions or user interaction. Although no sensitive session data is exposed, the ability to forcibly log out users can disrupt availability and workflow. The issue was fixed in OpenProject 16.6.5 and 17.

Impact

For European organizations using vulnerable OpenProject versions, this vulnerability can lead to denial-of-service conditions by allowing attackers to forcibly log out legitimate users. This disruption can affect productivity, especially in environments relying heavily on OpenProject for project management and collaboration. Although no confidential information is exposed, the forced session termination could be leveraged in targeted attacks to disrupt workflows or as part of a broader attack strategy. Organizations with many users or critical projects managed via OpenProject may experience operational impacts. Additionally, repeated forced logouts could lead to user frustration and potential loss of trust in the platform's reliability. Since the vulnerability requires no authentication or user interaction, it poses a moderate risk if the OpenProject instance is exposed to untrusted networks or the internet.

Summary

CVE-2026-23646 is a vulnerability categorized under CWE-488 (Exposure of Data Element to Wrong Session) affecting the open-source project management software OpenProject. The flaw exists in the session management functionality where users can view and delete their active sessions via the Account Settings interface. The vulnerability arises because the DELETE endpoint for sessions (`DELETE /my/sessions/:id`) does not properly verify that the session ID being deleted belongs to the authenticated user. Since session IDs are incremental integers, an attacker can enumerate session IDs and delete sessions belonging to other users, effectively logging them out. This unauthorized session termination does not expose sensitive session data such as IP addresses or browser identifiers, but it impacts availability by disrupting user sessions. The vulnerability requires no special permissions or user interaction, making it easier to exploit remotely. The issue was patched in OpenProject versions 16.6.5 and 17.0.1. The CVSS v3.1 score is 6.5 (medium), reflecting network attack vector, low complexity, no privileges required, no user interaction, unchanged scope, no confidentiality or integrity impact, but high impact on availability. No known exploits have been reported in the wild, and no temporary mitigations are available other than upgrading to fixed versions.

CWE-488Exposure of Data Element to Wrong Session (opens in a new tab)
Base weakness
The product does not sufficiently enforce boundaries between the states of different sessions, causing data to be provided to, or used by, the wrong session.
Architecture and Design
Protect the application's sessions from information leakage. Make sure that a session's data is not used or visible by other sessions.
Testing
Use a static analysis tool to scan the code for information leakage vulnerabilities (e.g. Singleton Member Field).
Architecture and Design
In a multithreading environment, storing user data in Servlet member fields introduces a data access race condition. Do not use member fields to store information in the Servlet.
Attack patterns
Session Credential Falsification through Prediction (opens in a new tab)
Reusing Session IDs (aka Session Replay) (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 26 Jan 2026, 20:10 UTC

WeaknessesCWE-488

Technical details

References

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