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Kimai has Missing Voter Check that Allows Cross-Team Timesheet Manipulation

Moderate severity GitHub Reviewed Published Apr 27, 2026 in kimai/kimai • Updated May 6, 2026

Package

composer kimai/kimai (Composer)

Affected versions

<= 2.55.0

Patched versions

2.56.0

Description

Summary

Any ROLE_TEAMLEAD user can enumerate, read, modify, and permanently delete timesheets belonging to any other user in the system — regardless of team membership. This enables data destruction (deleted billable hours), data tampering (forged timesheet durations), and full authorization bypass on timesheet resources. Verified against Kimai 2.52.0.

Details

TimesheetVoter::voteOnAttribute() maps permissions to own_timesheet or other_timesheet without checking team membership. The voter's own comment confirms this is a known gap:

// extend me for "team" support later on
if ($subject->getUser()?->getId() === $user->getId()) {
    $permission .= 'own';
} else {
    $permission .= 'other';
}

PoC

Tested against Kimai 2.52.0 Docker instance.

Setup:

  • User A (usera, ROLE_TEAMLEAD) owns timesheet ID 2 with description "Private timesheet - UserA only"
  • User B (userb, ROLE_TEAMLEAD) is NOT on any team with User A

User B reads User A's timesheet data:

GET /api/timesheets/2 HTTP/1.1
X-AUTH-USER: userb
X-AUTH-TOKEN: <userb_api_token>

Response: HTTP 200 — returns full timesheet record including description "Private timesheet - UserA only".

User B deletes User A's timesheet:

DELETE /api/timesheets/3 HTTP/1.1
X-AUTH-USER: userb
X-AUTH-TOKEN: <userb_api_token>

Response: HTTP 204 No Content — timesheet permanently deleted.

User B tampers User A's timesheet:

PATCH /api/timesheets/6 HTTP/1.1
X-AUTH-USER: userb
X-AUTH-TOKEN: <userb_api_token>
Content-Type: application/json

{"begin":"2026-03-24T08:00:00","end":"2026-03-24T18:00:00","project":1,"activity":1,"description":"TAMPERED","exported":false,"billable":false}

Response: HTTP 200 OK — duration inflated from 3600s to 36000s, description overwritten.

Note: ROLE_USER (userc) is correctly blocked — DELETE returns 403 and the actions endpoint returns an empty array. The vulnerability only affects ROLE_TEAMLEAD and above. Timesheet IDs are sequential integers, trivially enumerable.

Impact

Any authenticated user with ROLE_TEAMLEAD or above can:

  1. Permanently delete timesheets belonging to any user system-wide — destroying billable hours, payroll data, and project billing history
  2. Silently alter timesheet descriptions, hours, and billing flags — forging hours up or down, directly affecting invoicing and payroll
  3. Enumerate all timesheet IDs (sequential integers) and access action metadata for arbitrary records

No user interaction required. ROLE_USER accounts are correctly restricted; the vulnerability is specific to ROLE_TEAMLEAD receiving global scope instead of team-scoped access.

Maintainers answer: why this is not eligible for a CVE

The behavior described matches the documented permission model. Per the Kimai documentation, the relevant permissions granted to ROLE_TEAMLEAD are:

  • edit_other_timesheet — Edit existing records of other users
  • delete_other_timesheet — Delete existing records of other users

These permissions were global by design, not team-scoped. The UI surfaces only the teamlead's own team timesheets, but the API has historically honored these permissions as documented: a role holding *_other_timesheet can act on any other user's timesheet. The inline comment // extend me for "team" support later on reflects this accurately — team-scoped enforcement was a planned enhancement, not a security control that existed and failed.

The report frames this as authorization bypass, but no authorization boundary is being crossed: ROLE_TEAMLEAD is operating within its documented permissions.

Kimai acknowledges that this behavior might not be expected, so while it will be treated as a feature request for team-scoped permission enforcement and not a vulnerability, it still track it as having security implications.

Solution

Team-scoped timesheet permission checks were added in 2.56.0.

Operators of Kimai <= 2.55 who need stricter isolation between teamleads should not grant ROLE_TEAMLEAD to users who must not act on other teams' timesheets.

References

@kevinpapst kevinpapst published to kimai/kimai Apr 27, 2026
Published to the GitHub Advisory Database May 6, 2026
Reviewed May 6, 2026
Last updated May 6, 2026

Severity

Moderate

CVSS overall score

This score calculates overall vulnerability severity from 0 to 10 and is based on the Common Vulnerability Scoring System (CVSS).
/ 10

CVSS v4 base metrics

Exploitability Metrics
Attack Vector Network
Attack Complexity Low
Attack Requirements None
Privileges Required Low
User interaction None
Vulnerable System Impact Metrics
Confidentiality None
Integrity High
Availability None
Subsequent System Impact Metrics
Confidentiality None
Integrity None
Availability None

CVSS v4 base metrics

Exploitability Metrics
Attack Vector: This metric reflects the context by which vulnerability exploitation is possible. This metric value (and consequently the resulting severity) will be larger the more remote (logically, and physically) an attacker can be in order to exploit the vulnerable system. The assumption is that the number of potential attackers for a vulnerability that could be exploited from across a network is larger than the number of potential attackers that could exploit a vulnerability requiring physical access to a device, and therefore warrants a greater severity.
Attack Complexity: This metric captures measurable actions that must be taken by the attacker to actively evade or circumvent existing built-in security-enhancing conditions in order to obtain a working exploit. These are conditions whose primary purpose is to increase security and/or increase exploit engineering complexity. A vulnerability exploitable without a target-specific variable has a lower complexity than a vulnerability that would require non-trivial customization. This metric is meant to capture security mechanisms utilized by the vulnerable system.
Attack Requirements: This metric captures the prerequisite deployment and execution conditions or variables of the vulnerable system that enable the attack. These differ from security-enhancing techniques/technologies (ref Attack Complexity) as the primary purpose of these conditions is not to explicitly mitigate attacks, but rather, emerge naturally as a consequence of the deployment and execution of the vulnerable system.
Privileges Required: This metric describes the level of privileges an attacker must possess prior to successfully exploiting the vulnerability. The method by which the attacker obtains privileged credentials prior to the attack (e.g., free trial accounts), is outside the scope of this metric. Generally, self-service provisioned accounts do not constitute a privilege requirement if the attacker can grant themselves privileges as part of the attack.
User interaction: This metric captures the requirement for a human user, other than the attacker, to participate in the successful compromise of the vulnerable system. This metric determines whether the vulnerability can be exploited solely at the will of the attacker, or whether a separate user (or user-initiated process) must participate in some manner.
Vulnerable System Impact Metrics
Confidentiality: This metric measures the impact to the confidentiality of the information managed by the VULNERABLE SYSTEM due to a successfully exploited vulnerability. Confidentiality refers to limiting information access and disclosure to only authorized users, as well as preventing access by, or disclosure to, unauthorized ones.
Integrity: This metric measures the impact to integrity of a successfully exploited vulnerability. Integrity refers to the trustworthiness and veracity of information. Integrity of the VULNERABLE SYSTEM is impacted when an attacker makes unauthorized modification of system data. Integrity is also impacted when a system user can repudiate critical actions taken in the context of the system (e.g. due to insufficient logging).
Availability: This metric measures the impact to the availability of the VULNERABLE SYSTEM resulting from a successfully exploited vulnerability. While the Confidentiality and Integrity impact metrics apply to the loss of confidentiality or integrity of data (e.g., information, files) used by the system, this metric refers to the loss of availability of the impacted system itself, such as a networked service (e.g., web, database, email). Since availability refers to the accessibility of information resources, attacks that consume network bandwidth, processor cycles, or disk space all impact the availability of a system.
Subsequent System Impact Metrics
Confidentiality: This metric measures the impact to the confidentiality of the information managed by the SUBSEQUENT SYSTEM due to a successfully exploited vulnerability. Confidentiality refers to limiting information access and disclosure to only authorized users, as well as preventing access by, or disclosure to, unauthorized ones.
Integrity: This metric measures the impact to integrity of a successfully exploited vulnerability. Integrity refers to the trustworthiness and veracity of information. Integrity of the SUBSEQUENT SYSTEM is impacted when an attacker makes unauthorized modification of system data. Integrity is also impacted when a system user can repudiate critical actions taken in the context of the system (e.g. due to insufficient logging).
Availability: This metric measures the impact to the availability of the SUBSEQUENT SYSTEM resulting from a successfully exploited vulnerability. While the Confidentiality and Integrity impact metrics apply to the loss of confidentiality or integrity of data (e.g., information, files) used by the system, this metric refers to the loss of availability of the impacted system itself, such as a networked service (e.g., web, database, email). Since availability refers to the accessibility of information resources, attacks that consume network bandwidth, processor cycles, or disk space all impact the availability of a system.
CVSS:4.0/AV:N/AC:L/AT:N/PR:L/UI:N/VC:N/VI:H/VA:N/SC:N/SI:N/SA:N/E:P

EPSS score

Weaknesses

Incorrect Authorization

The product performs an authorization check when an actor attempts to access a resource or perform an action, but it does not correctly perform the check. Learn more on MITRE.

CVE ID

No known CVE

GHSA ID

GHSA-9g2q-w3w2-vf7q

Source code

Credits

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