How severe is CVE-2026-39813?

CVE-2026-39813 has a CVSS 3.x base score of 9.8, rated critical severity. It is exploitable over network with low attack complexity, requires no privileges and no user interaction. Impact on confidentiality is high, integrity high, and availability high.

Is CVE-2026-39813 being actively exploited?

It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 17% (97th percentile), an estimate of the probability of exploitation in the next 30 days.

What products are affected by CVE-2026-39813?

CVE-2026-39813 affects Fortinet Fortisandbox. See the affected-products list for the exact vulnerable versions.

How do I fix CVE-2026-39813?

Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround. Given its critical severity, prioritise patching exposed systems.

Does CVE-2026-39813 have an EU (EUVD) identifier?

Yes. CVE-2026-39813 is tracked in the ENISA EU Vulnerability Database (EUVD) as EUVD-2026-22344.

When was CVE-2026-39813 published?

CVE-2026-39813 was published on 2026-04-14 and last updated on 2026-06-18.

CVE-2026-39813

CVE-2026-39813 is a critical-severity vulnerability in Fortinet Fortisandbox with a CVSS 3.x base score of 9.8. Its EPSS exploit-prediction score of 17% places it in the 97th percentile, indicating an elevated likelihood of exploitation. The underlying weakness is classified as CWE-24.

Key facts

Severity: Critical (CVSS 3.x base score 9.8)
EPSS exploit prediction: 17% (97th percentile)
Actively exploited: Not listed in CISA KEV
EU (EUVD) id: EUVD-2026-22344
Weakness: CWE-24
Affected product: Fortinet Fortisandbox
Published: 2026-04-14
Last modified: 2026-06-18

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.

Frequently asked questions

What is CVE-2026-39813?: 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.
How severe is CVE-2026-39813?: CVE-2026-39813 has a CVSS 3.x base score of 9.8, rated critical severity. It is exploitable over network with low attack complexity, requires no privileges and no user interaction. Impact on confidentiality is high, integrity high, and availability high.
Is CVE-2026-39813 being actively exploited?: It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 17% (97th percentile), an estimate of the probability of exploitation in the next 30 days.
What products are affected by CVE-2026-39813?: CVE-2026-39813 affects Fortinet Fortisandbox. See the affected-products list for the exact vulnerable versions.
How do I fix CVE-2026-39813?: Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround. Given its critical severity, prioritise patching exposed systems.
Does CVE-2026-39813 have an EU (EUVD) identifier?: Yes. CVE-2026-39813 is tracked in the ENISA EU Vulnerability Database (EUVD) as EUVD-2026-22344.
When was CVE-2026-39813 published?: CVE-2026-39813 was published on 2026-04-14 and last updated on 2026-06-18.

References

https://fortiguard.fortinet.com/psirt/FG-IR-26-112

Affected products (1)

cpe:2.3:a:fortinet:fortisandbox:*:*:*:*:*:*:*:*

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