Nagios XI: Improper Neutralization of Special Elements used in an OS Command
CVE-2026-119742 is a high-severity improper neutralization of special elements used in an OS command vulnerability in Nagios XI from Nagios Enterprises, LLC., with a CVSS 3.1 base score of 7.2 out of 10. It can be exploited remotely over the network by an attacker with administrator privileges, without any action from a user. The record lists version 2026R2 as the first without the flaw, so updating Nagios XI to that release or later removes the exposure. There is no confirmed exploitation so far. EPSS estimates a 4.09% chance of exploitation within 30 days, which is in the top 9.11% of all scored CVEs.
High severity with no evidence of exploitation so far.
What to do
- Update Nagios XI to 2026R2 or a later version.
Affected products and versions
| Vendor | Product | Affected versions | Fixed in |
|---|---|---|---|
| Nagios Enterprises | Nagios XI | before 2026R2 | 2026R2 |
Version data comes from the organisation that assigned the CVE. Confirm against the vendor advisory before deciding you are unaffected.
How the severity score breaks down
- Attack vector
- NetworkCan be exploited remotely over a network, including the internet.
- Attack complexity
- LowNo special conditions are needed; the attack works reliably.
- Privileges required
- HighAdministrator-level access is required first.
- User interaction
- NoneNo action by a victim is required.
- Scope
- UnchangedImpact stays within the vulnerable component.
- Confidentiality
- HighAll data handled by the component can be read.
- Integrity
- HighData or code can be modified at will.
- Availability
- HighThe component can be taken down completely.
Vector: CVSS:3.1/AV:N/AC:L/PR:H/UI:N/S:U/C:H/I:H/A:H. Scored by CNA (vulncheck.com).
| Scoring system | Score | Severity | Scored by |
|---|---|---|---|
| CVSS 4.0 | 8.6 | High | CNA (vulncheck.com) |
| CVSS 3.1 | 7.2 | High | CNA (vulncheck.com) |
Official description
Nagios XI before 2026R2 contains an OS command injection vulnerability in the MIB upload feature where the install_mib() function in mibs.php sanitizes uploaded filenames with an incomplete character-substitution filter that omits semicolons, pipes, and non-space IFS whitespace characters before passing them to a grep command run via exec(). An authenticated administrator can upload a MIB file with a crafted filename using tab characters to bypass the deny-list and pipe to sh via a multipart POST request to mibs.php, resulting in arbitrary OS command execution as the web server user.
Source: the CVE record as published by its numbering authority, via NVD and CVE.org.
The underlying weakness: Improper Neutralization of Special Elements used in an OS Command
The product constructs all or part of an OS command using externally-influenced input from an upstream component, but it does not neutralize or incorrectly neutralizes special elements that could modify the intended OS command before it is sent to a downstream component.
How developers prevent this class of flaw
- If at all possible, use library calls rather than external processes to recreate the desired functionality.
- For any data that will be used to generate a command to be executed, keep as much of that data out of external control as possible. For example, in web applications, this may require storing the data locally in the session's state instead of sending it out to the client in a hidden form field.
- For any security checks that are performed on the client side, ensure that these checks are duplicated on the server side, in order to avoid CWE-602. Attackers can bypass the client-side checks by modifying values after the checks have been performed, or by changing the client to remove the client-side checks entirely. Then, these modified values would be submitted to the server.
More Improper Neutralization of Special Elements used in an OS Command vulnerabilities (CWE-78)
Timeline
- CVE record published.
- CISA published its SSVC assessment (exploitation: none, automatable: no, technical impact: total).
References
Other references
Other vulnerabilities in Nagios XI
- 7.5 High severity
- 7.5 High severity
- 7.4 High severity
Recent Improper Neutralization of Special Elements used in an OS Command vulnerabilities
- 7.3 High severity
- 8.8 High severity
- 8.1 High severity
- 7.8 High severity
- 8.8 High severity
- 7.2 High severity
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