Executive Intelligence Brief

A critical vulnerability, CVE-2026-80202, has been discovered in Kimai, an open-source timesheet management system. This vulnerability has a CVSS score of 8.8 and allows authenticated users with certain roles to read, modify, and delete timesheets of any user, regardless of team membership. The affected versions are before 2.56.0, and immediate patching to version 2.56.0 or later is strongly recommended.

Threat Overview

Kimai is a widely used open-source timesheet management system designed to help teams track working hours and manage projects efficiently. The vulnerability, CVE-2026-80202, affects Kimai versions before 2.56.0 and is caused by a lack of proper team membership checks in the TimesheetVoter::voteOnAttribute() method. This method maps permissions to either 'own_timesheet' or 'other_timesheet', but fails to enforce team membership, allowing users with ROLE_TEAMLEAD or similar roles to access and manipulate timesheets system-wide.

Technical Deep Dive

Vulnerability Classification

The vulnerability is classified as CWE-863, which involves an authorization bypass issue. This occurs when a system fails to properly enforce authorization rules, allowing unauthorized access to sensitive data or functionality.

Root Cause Analysis

The root cause of this vulnerability is the lack of team membership checks in the TimesheetVoter::voteOnAttribute() method. This method is responsible for determining whether a user has the necessary permissions to perform certain actions on timesheets. However, due to the missing checks, users with ROLE_TEAMLEAD or similar roles can access and manipulate timesheets of any user, regardless of team membership.

Attack Vector & Chain

The attack vector for this vulnerability involves an authenticated user with ROLE_TEAMLEAD or similar roles sending a crafted API request to access, modify, or delete timesheets of other users. The attack complexity is low, as the attacker only needs to be authenticated and have the required role. The vulnerability allows for high impact, as an attacker can read, modify, and permanently delete timesheets system-wide.

Exploitation Scenario Walkthrough

Scenario: Unauthorized Timesheet Access and Manipulation
Reconnaissance: An attacker discovers that the target organization uses Kimai for timesheet management and identifies a user with ROLE_TEAMLEAD or similar roles.
Weaponization: The attacker prepares a crafted API request to access or manipulate timesheets of other users.
Delivery & Exploitation: The attacker sends the crafted API request to the Kimai server, which processes the request without proper team membership checks, allowing the attacker to access or manipulate timesheets system-wide.
Post-Exploitation: The attacker can read, modify, or permanently delete timesheets of any user, potentially leading to data tampering or exposure.
Impact Realization: The attacker achieves unauthorized access to sensitive timesheet data, potentially leading to data breaches or operational disruptions.

Exploitation in the Wild

The vulnerability is not currently being actively exploited in the wild. However, given its severity and the availability of exploit details, there is a high likelihood of exploitation in the near future.

Impact Analysis

Direct Impact

The direct impact of this vulnerability is high, as an attacker can read, modify, and permanently delete timesheets of any user system-wide. This can lead to data tampering, exposure, or loss of sensitive information.

Downstream & Cascading Effects

The downstream effects of this vulnerability include potential data breaches, operational disruptions, and reputational damage. Additionally, the vulnerability may have regulatory implications, particularly if the affected organization is subject to data protection regulations.

Affected Products & Versions

The vulnerability affects Kimai versions before 2.56.0. The fixed version is 2.56.0 or later.

Detection & Threat Hunting

Indicators of Compromise

Indicators of compromise (IoCs) for this vulnerability include unusual API requests to access or manipulate timesheets, as well as logs showing access to timesheets by users who should not have permission.

Detection Rules & Signatures

Detection rules for this vulnerability should monitor API requests to the Kimai system, particularly those related to timesheet access or manipulation. Behavioral patterns that indicate exploitation include repeated or suspicious requests to access or modify timesheets by users with ROLE_TEAMLEAD or similar roles.

Threat Hunting Queries

Threat hunting queries should focus on identifying unusual patterns of API requests, particularly those related to timesheet access or manipulation. Queries should also look for logs showing access to timesheets by users who should not have permission.

Remediation & Hardening

Immediate Actions (0-24 hours)

1. **Patch to version 2.56.0 or later**: Immediately apply the patch to prevent exploitation of the vulnerability.
2. **Monitor for suspicious activity**: Closely monitor API requests and logs for signs of exploitation.

Short-Term Hardening (1-7 days)

1. **Implement additional security controls**: Consider implementing additional security controls, such as role-based access control and monitoring of API requests.
2. **Review and update roles and permissions**: Review and update roles and permissions to ensure that users only have access to necessary functionality and data.

Strategic Recommendations

1. **Regularly update and patch software**: Ensure that all software, including Kimai, is regularly updated and patched to prevent exploitation of known vulnerabilities.
2. **Implement a robust security program**: Implement a robust security program that includes monitoring, incident response, and security testing to identify and address potential vulnerabilities.

Analyst Assessment

The risk of this vulnerability is high, given its severity and the potential for exploitation. Organizations using Kimai should prioritize patching to version 2.56.0 or later to prevent exploitation. Additionally, organizations should monitor for suspicious activity and implement additional security controls to prevent similar vulnerabilities from being exploited in the future.

Sources

  • National Vulnerability Database (NVD) - CVE-2026-80202