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CVE-2021-40906

24
FAUCET Score

CVE-2021-40906 is a Reflected Cross-Site Scripting (XSS) vulnerability affecting CheckMK Raw Edition software versions 1.5.0 to 1.6.0, stemming from unsanitized input in an unauthenticated web service parameter. This medium-severity vulnerability (CVSS 6.1) allows an unauthenticated attacker to inject malicious HTML or client-side scripts, potentially leading to backdoor creation or session cookie theft if a user is authenticated. While the attack complexity is low, successful exploitation requires user interaction (UI:R) and access to the web service. There is no evidence of active exploitation, public exploit code (Metasploit, Nuclei, ExploitDB), or significant community discussion or media coverage.

Impacted Technologies

VendorProductVersion(s)CPE
>= 1.5.0, < 1.6.0CPE matchmatch criteria
cpe:2.3:a:checkmk:checkmk:*:*:*:*:*:*:*:*
1.6.0CPE matchmatch criteria
cpe:2.3:a:checkmk:checkmk:1.6.0:-:*:*:*:*:*:*
1.6.0CPE matchmatch criteria
cpe:2.3:a:checkmk:checkmk:1.6.0:b1:*:*:*:*:*:*
1.6.0CPE matchmatch criteria
cpe:2.3:a:checkmk:checkmk:1.6.0:b10:*:*:*:*:*:*
1.6.0CPE matchmatch criteria
cpe:2.3:a:checkmk:checkmk:1.6.0:b12:*:*:*:*:*:*

CVSS Data

CVSS version used by this source: 3.1

6.1MEDIUM

CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N

Attack Vector
NETWORK
Attack Complexity
LOW
Privileges Required
NONE
User Interaction
REQUIRED
Scope
CHANGED
Confidentiality Impact
LOW
Integrity Impact
LOW
Availability Impact
NONE
Exploitability Score
2.8
Impact Score
2.7
CvssVersion
3.1

Exploit Intelligence

EPSS Score
0.97%
Probability of exploitation in next 30 days
EPSS Percentile
58.4%
Percentile rank of EPSS score among Peer Group
As of 2026-07-27
Model: v2026.06.15
This CVE's current EPSS score of 0.0097 is in the 71st percentile among its peer group of 26,234 CVEs.

Social Chatter

The average CVE in this peer group has 0.0 Twitter, 0.0 Reddit, 0.1 Bluesky, 0.0 Mastodon, and 0.1 GitHub mentions.

Media Mentions

No media coverage found for this CVE.

The average CVE in this peer group has 0.1 InfoSec Media, 0.0 Vendor Blog, and 0.0 Security Researcher mentions.

Remediation

Remediation records are not available for this CVE.

References

github.com / Edgarloyola/CVE-2021-40906
Third Party Advisory