FortiSandbox: Path Traversal: '../filedir'
CVE-2026-39813 is a critical-severity path traversal: '../filedir' vulnerability in FortiSandbox from Fortinet, with a CVSS 3.1 base score of 9.8 out of 10. It can be exploited remotely over the network by an unauthenticated attacker, without any action from a user. Affected FortiSandbox versions: 5.0.0 through 5.0.5; 4.4.0 through 4.4.8. The record does not name a fixed version, so check the vendor advisory. There is no confirmed exploitation so far. EPSS estimates a 44% chance of exploitation within 30 days, which is in the top 1.23% of all scored CVEs.
Critical severity: a successful attack would have severe impact.
What to do
- Check which version of FortiSandbox you run against the affected versions below, and install the vendor's latest release.
- Read the advisory on fortiguard.fortinet.com for workarounds and exact fixed builds.
- Until you can update, restrict network access to the affected service so it is not reachable from untrusted networks.
Affected products and versions
| Vendor | Product | Affected versions | Fixed in |
|---|---|---|---|
| Fortinet | FortiSandbox | 5.0.0 through 5.0.5; 4.4.0 through 4.4.8 | Not stated |
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
- NoneNo account or login is needed.
- 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:N/UI:N/S:U/C:H/I:H/A:H. Scored by CNA (fortinet.com).
Official description
A path traversal: '../filedir' vulnerability in Fortinet FortiSandbox 5.0.0 through 5.0.5, FortiSandbox 4.4.0 through 4.4.8 may allow attacker to escalation of privilege via specially crafted HTTP requests.
Source: the CVE record as published by its numbering authority, via NVD and CVE.org.
The underlying weakness: Path Traversal: '../filedir'
The product uses external input to construct a pathname that should be within a restricted directory, but it does not properly neutralize../ sequences that can resolve to a location that is outside of that directory.
How developers prevent this class of flaw
- Inputs should be decoded and canonicalized to the application's current internal representation before being validated (CWE-180). Make sure that the application does not decode the same input twice (CWE-174). Such errors could be used to bypass allowlist validation schemes by introducing dangerous inputs after they have been checked.
Timeline
- CVE record published.
- CISA published its SSVC assessment (exploitation: none, automatable: yes, technical impact: total).
- Record last changed materially (score, affected products, status or references).
References
Other vulnerabilities in FortiSandbox
- 8.8 High severity
- 9.8 Critical severity
- 7.2 High severity
- 9.9 Critical severity
- 8.6 High severity
- 9.8 Critical severity
Recent Path Traversal: '../filedir' vulnerabilities
- 7.5 High severity
- 9.1 Critical severity
- 7.5 High severity
- 8.2 High severity
- 8.3 High severity
- 8.6 High severity
Spotted an error? Tell us.