CVE-2026-15227 Overview
CVE-2026-15227 is a missing authorization vulnerability in Checkmk, an IT infrastructure monitoring platform. The flaw allows an authenticated user without the Edit foreign Reports permission to modify reports owned by other users. The issue affects Checkmk versions prior to 2.5.0p10, 2.4.0p35, 2.3.0p49, and the end-of-life 2.2.0 branch. The vulnerability is categorized under [CWE-862] Missing Authorization and is network-exploitable with low privileges required.
Critical Impact
An authenticated Checkmk user can tamper with reports owned by other users, undermining reporting integrity across the monitoring environment.
Affected Products
- Checkmk versions prior to 2.5.0p10
- Checkmk versions prior to 2.4.0p35
- Checkmk versions prior to 2.3.0p49 and Checkmk 2.2.0 (EOL)
Discovery Timeline
- 2026-07-31 - CVE-2026-15227 published to NVD
- 2026-07-31 - Last updated in NVD database
Technical Details for CVE-2026-15227
Vulnerability Analysis
Checkmk enforces a permission model where the Edit foreign Reports capability governs whether a user can modify reports authored by other accounts. The vulnerable code path fails to consult this permission when handling report modification requests. As a result, any authenticated user can issue requests that alter reports belonging to other users, regardless of ownership.
The impact is limited to integrity of report objects. Confidentiality and availability of the underlying monitoring system are not directly affected, which is reflected in the CVSS 4.0 scoring where only the vulnerable system integrity metric is rated Low. The EPSS probability sits at 0.207% (10.903 percentile), consistent with a low-observation, authenticated-access flaw.
Root Cause
The root cause is a missing authorization check [CWE-862] on the report modification handler. The application authenticates the requesting user but does not verify report ownership or the presence of the Edit foreign Reports role permission before applying changes. Authorization was assumed at the user-interface layer rather than enforced at the server-side action endpoint.
Attack Vector
An attacker requires valid credentials to any Checkmk account that can access the reporting interface. Once authenticated, the attacker submits a modification request referencing a report owned by another user. The server processes the request and commits the changes without an ownership or permission check. No user interaction from the victim is required. See the Checkmk Security Advisory Werk 20003 for vendor-supplied technical detail.
Detection Methods for CVE-2026-15227
Indicators of Compromise
- Unexpected modifications to reports whose owner field does not match the acting user recorded in Checkmk audit logs.
- Report edit actions performed by accounts that do not hold the Edit foreign Reports permission.
- Audit log entries showing report changes originating from low-privilege user sessions.
Detection Strategies
- Review Checkmk audit logs (var/log/web.log and audit log entries) for report-edit actions and correlate the actor against the report owner.
- Baseline expected report editors per site and alert on any deviation from that list.
- Monitor HTTP requests to reporting endpoints for POST/PUT methods issued by non-administrative users.
Monitoring Recommendations
- Ingest Checkmk web and audit logs into a centralized log platform and build a rule that flags report modifications by users lacking the Edit foreign Reports role.
- Alert on abnormal volumes of report edits per user account within short time windows.
- Track version and patch level of every Checkmk site to confirm remediated builds are deployed.
How to Mitigate CVE-2026-15227
Immediate Actions Required
- Upgrade Checkmk to 2.5.0p10, 2.4.0p35, or 2.3.0p49 (or later) on all affected sites.
- Retire or migrate 2.2.0 deployments, which are end-of-life and will not receive a patch.
- Audit existing reports for unauthorized modifications and restore known-good versions where tampering is suspected.
Patch Information
Checkmk addressed the missing authorization check in the fixed builds listed in Werk 20003. The patched releases enforce the Edit foreign Reports permission on the server-side report modification handler, rejecting requests from users who do not own the report and lack the required role.
Workarounds
- Restrict access to the reporting interface to trusted operators until upgrades are applied.
- Reduce the number of accounts that can authenticate to the Checkmk GUI to shrink the attacker population.
- Remove or disable non-essential user accounts and enforce least-privilege role assignments across all Checkmk sites.
Disclaimer: This content was generated using AI. While we strive for accuracy, please verify critical information with official sources.
