Checkmk
CVE-2021-40905
HIGH
Vulnerability Assessment
| Weakness |
CWE
OWASP Top 10:2025
A06:2025 - Insecure Design
ASVS 5.0
V5 - File Handling File type validation, storage isolation
MITRE ATT&CK
2 techniques across 2 tactics: Command and Control, Persistence The technique list with ATT&CK links and the kill-chain view is part of the Basic plan and up. |
| Impact | CVSS score of 8.8 (HIGH). Attack characteristics: network attack vector, low complexity, no privileges required, user interaction required. Public proof-of-concept exploit code is available. EPSS exploitation probability: 2.81%. |
| Exploit ScenarioDerived | A remote attacker could upload malicious files that can be executed on the server by sending crafted requests to the affected application. No authentication is required to exploit this vulnerability. |
Get an e-mail when this CVE is exploited, patched or re-scored. Free account.
Alert meAnalysisAI
The web management console of CheckMK Enterprise Edition (versions 1.5.0 to 2.0.0p9) does not properly sanitise the uploading of ".mkp" files, which are Extension Packages, making remote code. Rated high severity (CVSS 8.8), this vulnerability is remotely exploitable, no authentication required, low attack complexity. Public exploit code available and no vendor patch available.
RemediationAI
No vendor patch is available at time of analysis. Monitor vendor advisories for updates. Validate file types server-side, store uploads outside webroot, use random filenames, scan for malware.
Affects your stack
Find out whether the stacks and servers you run are on an affected version.
Checking this CVE against your own stacks and servers is part of the Basic plan and up.
Technical ContextAI · show details
This vulnerability is classified as Unrestricted File Upload (CWE-434), which allows attackers to upload malicious files that can be executed on the server. The web management console of CheckMK Enterprise Edition (versions 1.5.0 to 2.0.0p9) does not properly sanitise the uploading of ".mkp" files, which are Extension Packages, making remote code execution possible. Successful exploitation requires access to the web management interface, either with valid credentials or with a hijacked session of a user with administrator role. NOTE: the vendor states that this is the intended behavior: admins are supposed to be able to execute code in this manner. Affected products include: Checkmk, Tribe29 Checkmk.
Know when Checkmk gets its next vulnerability
- Watch products and get an email when something new is published
- Check this CVE against your own stack and servers
- Exploit and PoC references, threat intelligence from 22 sources
No credit card · 7-day full trial
Severity by source
AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H
Primary rating from NVD · only source for this CVE.
CVSS VectorNVD
DescriptionNVD
The web management console of CheckMK Enterprise Edition (versions 1.5.0 to 2.0.0p9) does not properly sanitise the uploading of ".mkp" files, which are Extension Packages, making remote code execution possible. Successful exploitation requires access to the web management interface, either with valid credentials or with a hijacked session of a user with administrator role. NOTE: the vendor states that this is the intended behavior: admins are supposed to be able to execute code in this manner.
Threat Intelligence Overview
NVD
CVE.org
EPSS
GitHub
VulDB
How this decision was reached
The engine reads each signal below and applies a fixed list of rules from top to bottom. The first rule that matches sets the recommended action – like a statement, every line is shown.
What every action level means
SSVC AssessmentENISA
Priority Score
Attack Technique
Malicious file upload attacks exploit insufficient validation when web applications accept user-provided files.
Remote Code Execution represents the critical moment when an attacker successfully runs arbitrary code on a target system without physical access.
Affected Products (CPE)NVD
Check_MK before 1.2.8p26 mishandles certain errors within the failed-login save feature because of a race condition, whi
The web management console of CheckMK Raw Edition (versions 1.5.0 to 1.6.0) allows a misconfiguration of the web-app Dok
Local privilege escalation in the Checkmk Windows Agent's Windows License plugin allows an authenticated low-privileged
Stored/transmitted cross-site scripting in Checkmk's distributed monitoring lets an attacker who already controls a remo
Authenticated path traversal in Checkmk's report scheduler lets a user with valid application credentials write report f
Improper restriction of excessive authentication attempts on some authentication methods in Checkmk before 2.3.0b5 (beta
The CheckMK management web console (versions 1.5.0 to 2.0.0) does not sanitise user input in various parameters of the W
Local privilege escalation in Checkmk allows site users with high privileges to escalate to root by manipulating site co
Bypass of two factor authentication in RestAPI in Checkmk < 2.3.0p16 and < 2.2.0p34 allows authenticated users to bypass
Improper neutralization of active check command arguments in Checkmk < 2.1.0p32, < 2.0.0p38, < 2.2.0p4 leads to arbitrar
Improper neutralization of livestatus command delimiters in the RestAPI in Checkmk < 2.0.0p36, < 2.1.0p28, and < 2.2.0b8
Insufficient authentication flow in Checkmk before 2.2.0p18, 2.1.0p38 and 2.0.0p39 allows attacker to use locked credent
Exploit-DB