CVE-2020-3120 [Medium] | Integer Overflow in Firepower Extensible Oper…

A vulnerability in the Cisco Discovery Protocol implementation for Cisco FXOS Software, Cisco IOS XR Software, and Cisco NX-OS Software could allow an unauthenticated, adjacent attacker to cause a reload of an affected device, resulting in a denial of service (DoS) condition. The vulnerability is due to a missing check when the affected software processes Cisco Discovery Protocol messages. An attacker could exploit this vulnerability by sending a malicious Cisco Discovery Protocol packet to an affected device. A successful exploit could allow the attacker to exhaust system memory, causing the device to reload. Cisco Discovery Protocol is a Layer 2 protocol. To exploit this vulnerability, an attacker must be in the same broadcast domain as the affected device (Layer 2 adjacent).

#	Date	Old EPSS score	New EPSS score	Delta (New - Old)
1	2026-06-15	0.32%	2.03%	+1.71%
2	2025-11-21	0.14%	0.32%	+0.17%
3	2025-11-18	—	0.14%	—

Date

Old EPSS score

New EPSS score

Delta (New - Old)

2026-06-15

0.32%

2.03%

+1.71%

2025-11-21

0.14%

0.32%

+0.17%

2025-11-18

—

0.14%

—

Base score	Version	Severity	Vector	Exploitability	Impact	Score source
6.5	3.1	MEDIUM	`CVSS:3.1/AV:A/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H` Click to expand Attack vector (AV:A) Attacker has to be nearby on the network—same office, same link, that vibe—not the whole wide internet. 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:N) No account or special rights needed—anonymous or random user is enough. 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:N) Doesn’t really leak secrets in a meaningful way. Integrity (I:N) Data isn’t meaningfully altered or forged. Availability (A:H) Could take the service down hard or make it unusable for people who depend on it.	2.8	3.6	[email protected]
7.4	3.0	HIGH	`CVSS:3.0/AV:A/AC:L/PR:N/UI:N/S:C/C:N/I:N/A:H` Click to expand Attack vector (AV:A) Attacker has to be nearby on the network—same office, same link, that vibe—not the whole wide internet. 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:N) No account or special rights needed—anonymous or random user is enough. User interaction (UI:N) Nobody has to click “OK” or open a trap file; it can work without a victim helping. Scope (S:C) Breaking this can reach past the original component and bite other resources—bigger blast radius. Confidentiality (C:N) Doesn’t really leak secrets in a meaningful way. Integrity (I:N) Data isn’t meaningfully altered or forged. Availability (A:H) Could take the service down hard or make it unusable for people who depend on it.	2.8	4.0	[email protected]
6.1	2.0	MEDIUM	`AV:A/AC:L/Au:N/C:N/I:N/A:C` Click to expand Access vector (AV:A) Requires access to an adjacent network segment. Access complexity (AC:L) Exploitation conditions are straightforward and predictable. Authentication (AU:N) No authentication is required. Confidentiality impact (C:N) No confidentiality impact. Integrity impact (I:N) No integrity impact. Availability impact (A:C) Complete availability impact.	6.5	6.9	[email protected]

Base score

Version

Severity

Vector

Exploitability

Impact

Score source

6.5

3.1

MEDIUM

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

Attack vector (AV:A): Attacker has to be nearby on the network—same office, same link, that vibe—not the whole wide internet.
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:N): No account or special rights needed—anonymous or random user is enough.
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:N): Doesn’t really leak secrets in a meaningful way.
Integrity (I:N): Data isn’t meaningfully altered or forged.
Availability (A:H): Could take the service down hard or make it unusable for people who depend on it.

2.8

3.6

[email protected]

7.4

3.0

HIGH

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

Attack vector (AV:A): Attacker has to be nearby on the network—same office, same link, that vibe—not the whole wide internet.
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:N): No account or special rights needed—anonymous or random user is enough.
User interaction (UI:N): Nobody has to click “OK” or open a trap file; it can work without a victim helping.
Scope (S:C): Breaking this can reach past the original component and bite other resources—bigger blast radius.
Confidentiality (C:N): Doesn’t really leak secrets in a meaningful way.
Integrity (I:N): Data isn’t meaningfully altered or forged.
Availability (A:H): Could take the service down hard or make it unusable for people who depend on it.

2.8

4.0

[email protected]

6.1

2.0

MEDIUM

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

Access vector (AV:A): Requires access to an adjacent network segment.
Access complexity (AC:L): Exploitation conditions are straightforward and predictable.
Authentication (AU:N): No authentication is required.
Confidentiality impact (C:N): No confidentiality impact.
Integrity impact (I:N): No integrity impact.
Availability impact (A:C): Complete availability impact.

6.5

6.9

[email protected]

Affected software / configurations for CVE-2020-3120

Vendor	Product	Version	Raw CPE
cisco	firepower_extensible_operating_system	<= 2.3.1.173	cpe:2.3:o:cisco:firepower_extensible_operating_system::::::::
cisco	firepower_extensible_operating_system	>= 2.6, < 2.6.1.187	cpe:2.3:o:cisco:firepower_extensible_operating_system::::::::
cisco	firepower_extensible_operating_system	>= 2.7, < 2.7.1.106	cpe:2.3:o:cisco:firepower_extensible_operating_system::::::::
cisco	fxos	2.4	cpe:2.3:o:cisco:fxos:2.4:::::::*
cisco	ios_xr	5.2.5	cpe:2.3:o:cisco:ios_xr:5.2.5:::::::*
cisco	ios_xr	6.4.2	cpe:2.3:o:cisco:ios_xr:6.4.2:::::::*
cisco	ios_xr	6.5.3	cpe:2.3:o:cisco:ios_xr:6.5.3:::::::*
cisco	ios_xr	6.6.25	cpe:2.3:o:cisco:ios_xr:6.6.25:::::::*
cisco	ios_xr	7.0.1	cpe:2.3:o:cisco:ios_xr:7.0.1:::::::*
cisco	nx-os	>= 5.2, < 6.2\(29\)	cpe:2.3:o:cisco:nx-os::::::::
cisco	nx-os	>= 7.3, < 8.4\(1a\)	cpe:2.3:o:cisco:nx-os::::::::
cisco	nx-os	>= 5.2, < 5.2\(1\)sv5\(1.3\)	cpe:2.3:o:cisco:nx-os::::::::
cisco	nx-os	<= 5.2	cpe:2.3:o:cisco:nx-os::::::::
cisco	nx-os	< 5.2\(1\)sv3\(4.1b\)	cpe:2.3:o:cisco:nx-os::::::::
cisco	nx-os	>= 7.0\(3\)f2, < 9.3\(2\)	cpe:2.3:o:cisco:nx-os::::::::
cisco	nx-os	>= 7.0\(3\)i, < 7.0\(3\)i7\(8\)	cpe:2.3:o:cisco:nx-os::::::::
cisco	nx-os	< 7.3\(6\)n1\(1\)	cpe:2.3:o:cisco:nx-os::::::::
cisco	nx-os	< 6.2\(24\)	cpe:2.3:o:cisco:nx-os::::::::
cisco	nx-os	>= 7.2, < 7.3\(5\)d1\(1\)	cpe:2.3:o:cisco:nx-os::::::::
cisco	nx-os	>= 8.0, < 8.2\(5\)	cpe:2.3:o:cisco:nx-os::::::::
cisco	nx-os	>= 8.3, < 8.4\(2\)	cpe:2.3:o:cisco:nx-os::::::::
cisco	nx-os	< 13.2\(9b\)	cpe:2.3:o:cisco:nx-os::::::::
cisco	nx-os	>= 14.0, < 14.2\(1j\)	cpe:2.3:o:cisco:nx-os::::::::
cisco	ucs_manager	< 3.2\(3m\)	cpe:2.3:a:cisco:ucs_manager::::::::
cisco	ucs_manager	>= 4.0, < 4.0\(4g\)	cpe:2.3:a:cisco:ucs_manager::::::::

References for CVE-2020-3120

URL	Tags
http://packetstormsecurity.com/files/156203/Cisco-Discovery-Protocol-CDP-Remote-Device-Takeover.html	Third Party Advisory VDB Entry
https://tools.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-20200205-fxnxos-iosxr-cdp-dos	Vendor Advisory

URL

CVE-2020-3120 | Cisco FXOS, IOS XR, and NX-OS Software Cisco Discovery Protocol Denial of Service Vulnerability

Exploit prediction scoring system (EPSS) score for CVE-2020-3120

Common vulnerability scoring system (CVSS) metrics for CVE-2020-3120

Weakness enumeration for CVE-2020-3120

Affected software / configurations for CVE-2020-3120

References for CVE-2020-3120