How severe is CVE-2020-12820?

CVE-2020-12820 has a CVSS 3.x base score of 5.4, rated medium severity. It is exploitable over network with low attack complexity, requires low privileges and no user interaction. Impact on confidentiality is none, integrity low, and availability low.

Is CVE-2020-12820 being actively exploited?

It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 1% (54th percentile), an estimate of the probability of exploitation in the next 30 days.

What products are affected by CVE-2020-12820?

CVE-2020-12820 affects Fortinet Fortios. See the affected-products list for the exact vulnerable versions.

How do I fix CVE-2020-12820?

Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround.

Does CVE-2020-12820 have an EU (EUVD) identifier?

Yes. CVE-2020-12820 is tracked in the ENISA EU Vulnerability Database (EUVD) as EUVD-2020-5103.

When was CVE-2020-12820 published?

CVE-2020-12820 was published on 2024-12-19 and last updated on 2026-06-17.

CVE-2020-12820

CVE-2020-12820 is a medium-severity vulnerability in Fortinet Fortios with a CVSS 3.x base score of 5.4. It is not currently listed as actively exploited by CISA, and its EPSS exploit-prediction score is low. The underlying weakness is classified as CWE-787.

Key facts

Severity: Medium (CVSS 3.x base score 5.4)
EPSS exploit prediction: 1% (54th percentile)
Actively exploited: Not listed in CISA KEV
EU (EUVD) id: EUVD-2020-5103
Weakness: CWE-787
Affected product: Fortinet Fortios
Published: 2024-12-19
Last modified: 2026-06-17

Description

Under non-default configuration, a stack-based buffer overflow in FortiOS version 6.0.10 and below, version 5.6.12 and below may allow a remote attacker authenticated to the SSL VPN to crash the FortiClient NAC daemon (fcnacd) and potentially execute arbitrary code via requesting a large FortiClient file name. We are not aware of proof of concept code successfully achieving the latter.

Frequently asked questions

What is CVE-2020-12820?: Under non-default configuration, a stack-based buffer overflow in FortiOS version 6.0.10 and below, version 5.6.12 and below may allow a remote attacker authenticated to the SSL VPN to crash the FortiClient NAC daemon (fcnacd) and potentially execute arbitrary code via requesting a large FortiClient file name. We are not aware of proof of concept code successfully achieving the latter.
How severe is CVE-2020-12820?: CVE-2020-12820 has a CVSS 3.x base score of 5.4, rated medium severity. It is exploitable over network with low attack complexity, requires low privileges and no user interaction. Impact on confidentiality is none, integrity low, and availability low.
Is CVE-2020-12820 being actively exploited?: It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 1% (54th percentile), an estimate of the probability of exploitation in the next 30 days.
What products are affected by CVE-2020-12820?: CVE-2020-12820 affects Fortinet Fortios. See the affected-products list for the exact vulnerable versions.
How do I fix CVE-2020-12820?: Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround.
Does CVE-2020-12820 have an EU (EUVD) identifier?: Yes. CVE-2020-12820 is tracked in the ENISA EU Vulnerability Database (EUVD) as EUVD-2020-5103.
When was CVE-2020-12820 published?: CVE-2020-12820 was published on 2024-12-19 and last updated on 2026-06-17.

References

https://fortiguard.fortinet.com/psirt/FG-IR-20-083

Affected products (1)

cpe:2.3:o:fortinet:fortios:*:*:*:*:*:*:*:*

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