CVE-2021-40344
In the Custom Includes section of the Admin panel, an administrator can upload files with arbitrary extensions as long as the MIME type corresponds to an image.
Does this matter?
EPSS puts the probability of exploitation in the next 30 days at 64.8%, higher than 99% of all known CVEs. Patch or mitigate before the next change window.
Description
An issue was discovered in Nagios XI 5.8.5. In the Custom Includes section of the Admin panel, an administrator can upload files with arbitrary extensions as long as the MIME type corresponds to an image. Therefore it is possible to upload a crafted PHP script to achieve remote command execution.
- CVSS 3.1
- 7.2 HIGHCVSS:3.1/AV:N/AC:L/PR:H/UI:N/S:U/C:H/I:H/A:H
- EPSS
- 64.80% probability · 99th percentile
- Public exploits
- None in Exploit-DB
- CISA KEV
- Not listed
- Weakness
- CWE-434
- Affected
- nagios/nagios xi
- Source
- cve@mitre.org
EPSS moved from 64.8% on 20 September 2026 to 64.8% on 3 November 2026. The dashed line is the ten per cent mark our analysts treat as “patch before the next change window”.
References
- https://assets.nagios.com/downloads/nagiosxi/CHANGES-5.TXTRelease Notes, Vendor Advisory
- https://synacktiv.comNot Applicable
- https://www.synacktiv.com/sites/default/files/2021-10/Nagios_XI_multiple_vulnerabilities_0.pdfExploit, Third Party Advisory
- https://assets.nagios.com/downloads/nagiosxi/CHANGES-5.TXTRelease Notes, Vendor Advisory
- https://synacktiv.comNot Applicable
- https://www.synacktiv.com/sites/default/files/2021-10/Nagios_XI_multiple_vulnerabilities_0.pdfExploit, Third Party Advisory
Source: NVD record, EPSS from FIRST.org, KEV from CISA, exploits from Exploit-DB. Refreshed daily. Download this record as JSON.