CVE-2020-3166 [Medium] | Input Validation Bypass in Firepower Threat Defense

A vulnerability in the CLI of Cisco FXOS Software could allow an authenticated, local attacker to read or write arbitrary files on the underlying operating system (OS). The vulnerability is due to insufficient input validation. An attacker could exploit this vulnerability by including crafted arguments to a specific CLI command. A successful exploit could allow the attacker to read or write to arbitrary files on the underlying OS.

#	Date	Old EPSS score	New EPSS score	Delta (New - Old)
1	2025-11-21	0.05%	0.17%	+0.12%
2	2025-11-18	0.17%	0.05%	-0.12%
3	2025-05-15	—	0.17%	—

Date

Old EPSS score

New EPSS score

Delta (New - Old)

2025-11-21

0.05%

0.17%

+0.12%

2025-11-18

0.17%

0.05%

-0.12%

2025-05-15

—

0.17%

—

Base score	Version	Severity	Vector	Exploitability	Impact	Score source
6.7	3.1	MEDIUM	`CVSS:3.1/AV:L/AC:L/PR:H/UI:N/S:U/C:H/I:H/A:H` Click to expand Attack vector (AV:L) They already need access on the box, or another person has to do something wrong; it’s not a remote drive-by. Attack complexity (AC:L) Once they can reach the bug, pulling it off is straightforward—no weird race conditions or rare setup. Privileges required (PR:H) They need powerful rights—admin, root, or similar—before this pays off. User interaction (UI:N) Nobody has to click “OK” or open a trap file; it can work without a victim helping. Scope (S:U) Damage stays in the same “trust bubble” as the broken component—no big spill into unrelated systems. Confidentiality (C:H) Serious risk that confidential data gets exposed in a big way. Integrity (I:H) They could widely tamper with or forge data—trust in the data is badly hurt. Availability (A:H) Could take the service down hard or make it unusable for people who depend on it.	0.8	5.9	[email protected]
4.2	3.0	MEDIUM	`CVSS:3.0/AV:L/AC:L/PR:H/UI:N/S:U/C:L/I:L/A:L` Click to expand Attack vector (AV:L) They already need access on the box, or another person has to do something wrong; it’s not a remote drive-by. Attack complexity (AC:L) Once they can reach the bug, pulling it off is straightforward—no weird race conditions or rare setup. Privileges required (PR:H) They need powerful rights—admin, root, or similar—before this pays off. User interaction (UI:N) Nobody has to click “OK” or open a trap file; it can work without a victim helping. Scope (S:U) Damage stays in the same “trust bubble” as the broken component—no big spill into unrelated systems. Confidentiality (C:L) Some sensitive info could get out, but not a total data dump. Integrity (I:L) Attackers could change some data, but it’s limited—not everything goes. Availability (A:L) Might cause slowdowns, glitches, or partial disruption—not a full brick.	0.8	3.4	[email protected]
4.6	2.0	MEDIUM	`AV:L/AC:L/Au:N/C:P/I:P/A:P` Click to expand Access vector (AV:L) Requires local access to the target system. Access complexity (AC:L) Exploitation conditions are straightforward and predictable. Authentication (AU:N) No authentication is required. Confidentiality impact (C:P) Partial confidentiality impact. Integrity impact (I:P) Partial integrity impact. Availability impact (A:P) Partial availability impact.	3.9	6.4	[email protected]

Base score

Version

Severity

Vector

Exploitability

Impact

Score source

6.7

3.1

MEDIUM

CVSS:3.1/AV:L/AC:L/PR:H/UI:N/S:U/C:H/I:H/A:H Click to expand

Attack vector (AV:L): They already need access on the box, or another person has to do something wrong; it’s not a remote drive-by.
Attack complexity (AC:L): Once they can reach the bug, pulling it off is straightforward—no weird race conditions or rare setup.
Privileges required (PR:H): They need powerful rights—admin, root, or similar—before this pays off.
User interaction (UI:N): Nobody has to click “OK” or open a trap file; it can work without a victim helping.
Scope (S:U): Damage stays in the same “trust bubble” as the broken component—no big spill into unrelated systems.
Confidentiality (C:H): Serious risk that confidential data gets exposed in a big way.
Integrity (I:H): They could widely tamper with or forge data—trust in the data is badly hurt.
Availability (A:H): Could take the service down hard or make it unusable for people who depend on it.

0.8

5.9

[email protected]

4.2

3.0

MEDIUM

CVSS:3.0/AV:L/AC:L/PR:H/UI:N/S:U/C:L/I:L/A:L Click to expand

Attack vector (AV:L): They already need access on the box, or another person has to do something wrong; it’s not a remote drive-by.
Attack complexity (AC:L): Once they can reach the bug, pulling it off is straightforward—no weird race conditions or rare setup.
Privileges required (PR:H): They need powerful rights—admin, root, or similar—before this pays off.
User interaction (UI:N): Nobody has to click “OK” or open a trap file; it can work without a victim helping.
Scope (S:U): Damage stays in the same “trust bubble” as the broken component—no big spill into unrelated systems.
Confidentiality (C:L): Some sensitive info could get out, but not a total data dump.
Integrity (I:L): Attackers could change some data, but it’s limited—not everything goes.
Availability (A:L): Might cause slowdowns, glitches, or partial disruption—not a full brick.

0.8

3.4

[email protected]

4.6

2.0

MEDIUM

AV:L/AC:L/Au:N/C:P/I:P/A:P Click to expand

Access vector (AV:L): Requires local access to the target system.
Access complexity (AC:L): Exploitation conditions are straightforward and predictable.
Authentication (AU:N): No authentication is required.
Confidentiality impact (C:P): Partial confidentiality impact.
Integrity impact (I:P): Partial integrity impact.
Availability impact (A:P): Partial availability impact.

3.9

6.4

[email protected]

Affected software / configurations for CVE-2020-3166

Vendor	Product	Version	Raw CPE
cisco	firepower_threat_defense	>= 6.2.2, < 6.2.3.16	cpe:2.3:a:cisco:firepower_threat_defense::::::::
cisco	firepower_threat_defense	>= 6.3.0, < 6.5.0.3	cpe:2.3:a:cisco:firepower_threat_defense::::::::
cisco	adaptive_security_appliance_software	>= 9.8, < 9.9.2.66	cpe:2.3:o:cisco:adaptive_security_appliance_software::::::::
cisco	adaptive_security_appliance_software	>= 9.10, < 9.13.1.5	cpe:2.3:o:cisco:adaptive_security_appliance_software::::::::
cisco	firepower_extensible_operating_system	< 2.2.2.97	cpe:2.3:o:cisco:firepower_extensible_operating_system::::::::
cisco	firepower_extensible_operating_system	>= 2.3, < 2.3.1.155	cpe:2.3:o:cisco:firepower_extensible_operating_system::::::::
cisco	firepower_extensible_operating_system	>= 2.4, < 2.4.1.238	cpe:2.3:o:cisco:firepower_extensible_operating_system::::::::
cisco	firepower_extensible_operating_system	>= 2.6, < 2.6.1.157	cpe:2.3:o:cisco:firepower_extensible_operating_system::::::::

References for CVE-2020-3166

URL	Tags
https://tools.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-20200226-fxos-cli-file	Vendor Advisory

URL

CVE-2020-3166 | Cisco FXOS Software CLI Arbitrary File Read and Write Vulnerability

Exploit prediction scoring system (EPSS) score for CVE-2020-3166

Common vulnerability scoring system (CVSS) metrics for CVE-2020-3166

Weakness enumeration for CVE-2020-3166

Affected software / configurations for CVE-2020-3166

References for CVE-2020-3166