CVE-2022-20756 [High] | Denial of Service in Identity Services Engine

A vulnerability in the RADIUS feature of Cisco Identity Services Engine (ISE) could allow an unauthenticated, remote attacker to cause the affected system to stop processing RADIUS packets. This vulnerability is due to improper handling of certain RADIUS requests. An attacker could exploit this vulnerability by attempting to authenticate to a network or a service where the access server is using Cisco ISE as the RADIUS server. A successful exploit could allow the attacker to cause Cisco ISE to stop processing RADIUS requests, causing authentication/authorization timeouts, which would then result in legitimate requests being denied access. Note: To recover the ability to process RADIUS packets, a manual restart of the affected Policy Service Node (PSN) is required. See the Details section for more information.

#	Date	Old EPSS score	New EPSS score	Delta (New - Old)
1	2026-06-15	1.13%	1.39%	+0.26%
2	2025-04-24	1.61%	1.13%	-0.48%
3	2025-04-20	—	1.61%	—

Date

Old EPSS score

New EPSS score

Delta (New - Old)

2026-06-15

1.13%

1.39%

+0.26%

2025-04-24

1.61%

1.13%

-0.48%

2025-04-20

—

1.61%

—

Base score	Version	Severity	Vector	Exploitability	Impact	Score source
8.6	3.1	HIGH	`CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:N/I:N/A:H` Click to expand Attack vector (AV:N) Could be attacked over the internet or any normal routed network—not just someone sitting at the machine. 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.	3.9	4.0	[email protected]
7.5	3.1	HIGH	`CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H` Click to expand Attack vector (AV:N) Could be attacked over the internet or any normal routed network—not just someone sitting at the machine. 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.	3.9	3.6	[email protected]
5.0	2.0	MEDIUM	`AV:N/AC:L/Au:N/C:N/I:N/A:P` Click to expand Access vector (AV:N) Can be exploited remotely over network reachability. 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:P) Partial availability impact.	10.0	2.9	[email protected]

Base score

Version

Severity

Vector

Exploitability

Impact

Score source

8.6

3.1

HIGH

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

Attack vector (AV:N): Could be attacked over the internet or any normal routed network—not just someone sitting at the machine.
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.

3.9

4.0

[email protected]

7.5

3.1

HIGH

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

Attack vector (AV:N): Could be attacked over the internet or any normal routed network—not just someone sitting at the machine.
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.

3.9

3.6

[email protected]

5.0

2.0

MEDIUM

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

Access vector (AV:N): Can be exploited remotely over network reachability.
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:P): Partial availability impact.

10.0

2.9

[email protected]

Affected software / configurations for CVE-2022-20756

Vendor	Product	Version	Raw CPE
cisco	identity_services_engine	2.2.0	cpe:2.3:a:cisco:identity_services_engine:2.2.0:patch17::::::
cisco	identity_services_engine	2.4.0	cpe:2.3:a:cisco:identity_services_engine:2.4.0:patch12::::::
cisco	identity_services_engine	2.4.0	cpe:2.3:a:cisco:identity_services_engine:2.4.0:patch13::::::
cisco	identity_services_engine	2.4.0	cpe:2.3:a:cisco:identity_services_engine:2.4.0:patch14::::::
cisco	identity_services_engine	2.6.0	cpe:2.3:a:cisco:identity_services_engine:2.6.0:patch10::::::
cisco	identity_services_engine	2.6.0	cpe:2.3:a:cisco:identity_services_engine:2.6.0:patch5::::::
cisco	identity_services_engine	2.6.0	cpe:2.3:a:cisco:identity_services_engine:2.6.0:patch6::::::
cisco	identity_services_engine	2.6.0	cpe:2.3:a:cisco:identity_services_engine:2.6.0:patch7::::::
cisco	identity_services_engine	2.6.0	cpe:2.3:a:cisco:identity_services_engine:2.6.0:patch8::::::
cisco	identity_services_engine	2.6.0	cpe:2.3:a:cisco:identity_services_engine:2.6.0:patch9::::::
cisco	identity_services_engine	2.7.0	cpe:2.3:a:cisco:identity_services_engine:2.7.0:patch2::::::
cisco	identity_services_engine	2.7.0	cpe:2.3:a:cisco:identity_services_engine:2.7.0:patch3::::::
cisco	identity_services_engine	2.7.0	cpe:2.3:a:cisco:identity_services_engine:2.7.0:patch4::::::
cisco	identity_services_engine	2.7.0.356	cpe:2.3:a:cisco:identity_services_engine:2.7.0.356:patch1::::::
cisco	identity_services_engine	3.0.0	cpe:2.3:a:cisco:identity_services_engine:3.0.0:-::::::
cisco	identity_services_engine	3.1	cpe:2.3:a:cisco:identity_services_engine:3.1:-::::::

References for CVE-2022-20756

URL	Tags
https://tools.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-ise-dos-JLh9TxBp	Vendor Advisory

URL

CVE-2022-20756 | Cisco Identity Services Engine RADIUS Service Denial of Service Vulnerability

Exploit prediction scoring system (EPSS) score for CVE-2022-20756

Common vulnerability scoring system (CVSS) metrics for CVE-2022-20756

Weakness enumeration for CVE-2022-20756

Affected software / configurations for CVE-2022-20756

References for CVE-2022-20756