Fastnetmon: Improper Neutralization of Special Elements used in an OS Command
CVE-2026-48695 is a high-severity improper neutralization of special elements used in an OS command vulnerability in Fastnetmon from Pavel-odintsov, with a CVSS 3.1 base score of 8.1 out of 10. It can be exploited remotely over the network by an attacker with a low-privileged account, without any action from a user. Affected Fastnetmon versions: 1.2.9 and earlier. The record does not name a fixed version, so check the vendor advisory. There is no confirmed exploitation so far. EPSS estimates a 1.07% chance of exploitation within 30 days, higher than 65% of scored CVEs.
High severity with no evidence of exploitation so far.
What to do
- Check which version of Fastnetmon you run against the affected versions below, and install the vendor's latest release.
Affected products and versions
| Vendor | Product | Affected versions | Fixed in |
|---|---|---|---|
| Pavel-odintsov | Fastnetmon | 1.2.9 and earlier | Not stated |
Version data comes from NVD's product matching. 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
- LowA basic user account is enough.
- 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
- NoneAvailability is not affected.
Vector: CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:N. Scored by NVD.
| Scoring system | Score | Severity | Scored by |
|---|---|---|---|
| CVSS 3.1 | 8.1 | High | NVD |
| CVSS 3.1 | 8.1 | High | CISA (ADP) |
Official description
FastNetMon Community Edition through 1.2.9 contains an OS command injection vulnerability in the MikroTik router integration plugin. The _log() function in src/mikrotik_plugin/fastnetmon_mikrotik.php (lines 107-108) constructs shell commands by concatenating the $msg parameter directly into exec() calls: exec("echo `date` \"- {FASTNETMON] - " . $msg . " \" >> " . $FILE_LOG_TMP). This is identical in pattern to the Juniper plugin vulnerability. The $msg variable contains unsanitized attack data from command-line arguments. An attacker who can influence argv[] values can inject arbitrary shell commands. The fix is to replace exec() with file_put_contents() or use escapeshellarg().
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).
- Record last changed materially (score, affected products, status or references).
References
Third-party and government advisories
- lorikeetsecurity.com/blog/fastnetmon-cve-2026-48695-mikrotik-cmd-injectionThird Party Advisory
Other references
Other vulnerabilities in Fastnetmon
- 7.5 High severity
- 8.2 High severity
- 7.5 High severity
- 8.2 High severity
- 8.2 High severity
- 9.8 Critical severity
Recent Improper Neutralization of Special Elements used in an OS Command vulnerabilities
- 9.1 Critical severity
- 7.8 High severity
- 9.9 Critical severity
- 9.9 Critical severity
- 9.8 Critical severity
- 9.8 Critical severity
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