CVE-2020-12820
Under non-default configuration, a stack-based buffer overflow in FortiOS version 6.0.10 and...
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.
Attack profile
How easy it is to exploit
- Attack vector
- Network
- Complexity
- Low
- Privileges needed
- Low
- User interaction
- None
What an attacker can affect
- Confidentiality
- None
- Integrity
- Low
- Availability
- Low
Exploit likelihood
What each source reports
CVE List Score used
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.
- Record
CVE-2020-12820- CVSS 3.1
- 5.4 Medium
CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:L/A:L/E:U/RL:X/RC:X - Weakness
- CWE-121
- Updated
- 2026-11-02
EUVDEUVD-2020-5103
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.
- Record
EUVD-2020-5103- CVSS 3.1
- 5.4 Medium
CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:L/A:L/E:U/RL:X/RC:X - Updated
- 2026-11-03
GitHub AdvisoriesGHSA-8hp7-6mr2-85pv
Under non-default configuration, a stack-based buffer overflow in FortiOS version 6.0.10 and...
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.
- Record
GHSA-8hp7-6mr2-85pv- CVSS 3.1
- 5.4 Medium
CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:L/A:L - Weakness
- CWE-121, CWE-787
- Updated
- 2026-11-02
NVD
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.
- Record
CVE-2020-12820- CVSS 3.1
- 5.4 Medium
CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:L/A:L - CVSS 3.1
- 8.8 High
CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H - Weakness
- CWE-121, CWE-787
- Updated
- 2026-11-02
Affected products
History
| Recorded | Changed | Sources |
|---|---|---|
| aliases, published | EUVD | |
| first indexed | CVE List, GitHub Advisories, NVD |
Dates are when Every CVE recorded each change. Upstream dates may differ.
In short
CVE-2020-12820 is a medium vulnerability (CVSS 5.4) in Fortinet Fortios, published December 19, 2024. No source lists public exploit code. EPSS puts the chance of exploitation in the next 30 days at 0.89%, the 59th percentile. No source names a fixed version.