CVE-2021-1619 [Critical] | Denial of Service in Ios Xe

A vulnerability in the authentication, authorization, and accounting (AAA) function of Cisco IOS XE Software could allow an unauthenticated, remote attacker to bypass NETCONF or RESTCONF authentication and do either of the following: Install, manipulate, or delete the configuration of an affected device Cause memory corruption that results in a denial of service (DoS) on an affected device This vulnerability is due to an uninitialized variable. An attacker could exploit this vulnerability by sending a series of NETCONF or RESTCONF requests to an affected device. A successful exploit could allow the attacker to use NETCONF or RESTCONF to install, manipulate, or delete the configuration of a network device or to corrupt memory on the device, resulting a DoS.

#	Date	Old EPSS score	New EPSS score	Delta (New - Old)
1	2025-12-28	1.11%	0.87%	-0.25%
2	2025-12-27	0.87%	1.11%	+0.25%
3	2025-10-28	—	0.87%	—

Date

Old EPSS score

New EPSS score

Delta (New - Old)

2025-12-28

1.11%

0.87%

-0.25%

2025-12-27

0.87%

1.11%

+0.25%

2025-10-28

—

0.87%

—

Base score	Version	Severity	Vector	Exploitability	Impact	Score source
9.8	3.1	CRITICAL	`CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/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: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.	3.9	5.9	[email protected]
9.1	3.1	CRITICAL	`CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/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: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.	3.9	5.2	[email protected]
6.4	2.0	MEDIUM	`AV:N/AC:L/Au:N/C:N/I:P/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:P) Partial integrity impact. Availability impact (A:P) Partial availability impact.	10.0	4.9	[email protected]

Base score

Version

Severity

Vector

Exploitability

Impact

Score source

9.8

3.1

CRITICAL

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/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: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.

3.9

5.9

[email protected]

9.1

3.1

CRITICAL

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/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: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.

3.9

5.2

[email protected]

6.4

2.0

MEDIUM

AV:N/AC:L/Au:N/C:N/I:P/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:P): Partial integrity impact.
Availability impact (A:P): Partial availability impact.

10.0

4.9

[email protected]

Affected software / configurations for CVE-2021-1619

Vendor	Product	Version	Raw CPE
cisco	ios_xe	16.3.1	cpe:2.3:o:cisco:ios_xe:16.3.1:::::::*
cisco	ios_xe	16.3.1a	cpe:2.3:o:cisco:ios_xe:16.3.1a:::::::*
cisco	ios_xe	16.3.2	cpe:2.3:o:cisco:ios_xe:16.3.2:::::::*
cisco	ios_xe	16.3.3	cpe:2.3:o:cisco:ios_xe:16.3.3:::::::*
cisco	ios_xe	16.3.4	cpe:2.3:o:cisco:ios_xe:16.3.4:::::::*
cisco	ios_xe	16.3.5	cpe:2.3:o:cisco:ios_xe:16.3.5:::::::*
cisco	ios_xe	16.3.5b	cpe:2.3:o:cisco:ios_xe:16.3.5b:::::::*
cisco	ios_xe	16.3.6	cpe:2.3:o:cisco:ios_xe:16.3.6:::::::*
cisco	ios_xe	16.3.7	cpe:2.3:o:cisco:ios_xe:16.3.7:::::::*
cisco	ios_xe	16.3.8	cpe:2.3:o:cisco:ios_xe:16.3.8:::::::*
cisco	ios_xe	16.3.9	cpe:2.3:o:cisco:ios_xe:16.3.9:::::::*
cisco	ios_xe	16.3.10	cpe:2.3:o:cisco:ios_xe:16.3.10:::::::*
cisco	ios_xe	16.3.11	cpe:2.3:o:cisco:ios_xe:16.3.11:::::::*
cisco	ios_xe	16.4.1	cpe:2.3:o:cisco:ios_xe:16.4.1:::::::*
cisco	ios_xe	16.4.2	cpe:2.3:o:cisco:ios_xe:16.4.2:::::::*
cisco	ios_xe	16.4.3	cpe:2.3:o:cisco:ios_xe:16.4.3:::::::*
cisco	ios_xe	16.5.1	cpe:2.3:o:cisco:ios_xe:16.5.1:::::::*
cisco	ios_xe	16.5.1a	cpe:2.3:o:cisco:ios_xe:16.5.1a:::::::*
cisco	ios_xe	16.5.1b	cpe:2.3:o:cisco:ios_xe:16.5.1b:::::::*
cisco	ios_xe	16.5.2	cpe:2.3:o:cisco:ios_xe:16.5.2:::::::*
cisco	ios_xe	16.5.3	cpe:2.3:o:cisco:ios_xe:16.5.3:::::::*
cisco	ios_xe	16.6.1	cpe:2.3:o:cisco:ios_xe:16.6.1:::::::*
cisco	ios_xe	16.6.2	cpe:2.3:o:cisco:ios_xe:16.6.2:::::::*
cisco	ios_xe	16.6.3	cpe:2.3:o:cisco:ios_xe:16.6.3:::::::*
cisco	ios_xe	16.6.4	cpe:2.3:o:cisco:ios_xe:16.6.4:::::::*
cisco	ios_xe	16.6.4a	cpe:2.3:o:cisco:ios_xe:16.6.4a:::::::*
cisco	ios_xe	16.6.4s	cpe:2.3:o:cisco:ios_xe:16.6.4s:::::::*
cisco	ios_xe	16.6.5	cpe:2.3:o:cisco:ios_xe:16.6.5:::::::*
cisco	ios_xe	16.6.5a	cpe:2.3:o:cisco:ios_xe:16.6.5a:::::::*
cisco	ios_xe	16.6.5b	cpe:2.3:o:cisco:ios_xe:16.6.5b:::::::*
cisco	ios_xe	16.6.6	cpe:2.3:o:cisco:ios_xe:16.6.6:::::::*
cisco	ios_xe	16.6.7	cpe:2.3:o:cisco:ios_xe:16.6.7:::::::*
cisco	ios_xe	16.6.7a	cpe:2.3:o:cisco:ios_xe:16.6.7a:::::::*
cisco	ios_xe	16.6.8	cpe:2.3:o:cisco:ios_xe:16.6.8:::::::*
cisco	ios_xe	16.6.9	cpe:2.3:o:cisco:ios_xe:16.6.9:::::::*
cisco	ios_xe	16.7.1	cpe:2.3:o:cisco:ios_xe:16.7.1:::::::*
cisco	ios_xe	16.7.1a	cpe:2.3:o:cisco:ios_xe:16.7.1a:::::::*
cisco	ios_xe	16.7.1b	cpe:2.3:o:cisco:ios_xe:16.7.1b:::::::*
cisco	ios_xe	16.7.2	cpe:2.3:o:cisco:ios_xe:16.7.2:::::::*
cisco	ios_xe	16.7.3	cpe:2.3:o:cisco:ios_xe:16.7.3:::::::*
cisco	ios_xe	16.7.4	cpe:2.3:o:cisco:ios_xe:16.7.4:::::::*
cisco	ios_xe	16.8.1	cpe:2.3:o:cisco:ios_xe:16.8.1:::::::*
cisco	ios_xe	16.8.1a	cpe:2.3:o:cisco:ios_xe:16.8.1a:::::::*
cisco	ios_xe	16.8.1b	cpe:2.3:o:cisco:ios_xe:16.8.1b:::::::*
cisco	ios_xe	16.8.1c	cpe:2.3:o:cisco:ios_xe:16.8.1c:::::::*
cisco	ios_xe	16.8.1d	cpe:2.3:o:cisco:ios_xe:16.8.1d:::::::*
cisco	ios_xe	16.8.1e	cpe:2.3:o:cisco:ios_xe:16.8.1e:::::::*
cisco	ios_xe	16.8.1s	cpe:2.3:o:cisco:ios_xe:16.8.1s:::::::*
cisco	ios_xe	16.8.2	cpe:2.3:o:cisco:ios_xe:16.8.2:::::::*
cisco	ios_xe	16.8.3	cpe:2.3:o:cisco:ios_xe:16.8.3:::::::*
cisco	ios_xe	16.9.1	cpe:2.3:o:cisco:ios_xe:16.9.1:::::::*
cisco	ios_xe	16.9.1a	cpe:2.3:o:cisco:ios_xe:16.9.1a:::::::*
cisco	ios_xe	16.9.1b	cpe:2.3:o:cisco:ios_xe:16.9.1b:::::::*
cisco	ios_xe	16.9.1c	cpe:2.3:o:cisco:ios_xe:16.9.1c:::::::*
cisco	ios_xe	16.9.1d	cpe:2.3:o:cisco:ios_xe:16.9.1d:::::::*
cisco	ios_xe	16.9.1s	cpe:2.3:o:cisco:ios_xe:16.9.1s:::::::*
cisco	ios_xe	16.9.2	cpe:2.3:o:cisco:ios_xe:16.9.2:::::::*
cisco	ios_xe	16.9.2a	cpe:2.3:o:cisco:ios_xe:16.9.2a:::::::*
cisco	ios_xe	16.9.2s	cpe:2.3:o:cisco:ios_xe:16.9.2s:::::::*
cisco	ios_xe	16.9.3	cpe:2.3:o:cisco:ios_xe:16.9.3:::::::*
cisco	ios_xe	16.9.3a	cpe:2.3:o:cisco:ios_xe:16.9.3a:::::::*
cisco	ios_xe	16.9.3h	cpe:2.3:o:cisco:ios_xe:16.9.3h:::::::*
cisco	ios_xe	16.9.3s	cpe:2.3:o:cisco:ios_xe:16.9.3s:::::::*
cisco	ios_xe	16.9.4	cpe:2.3:o:cisco:ios_xe:16.9.4:::::::*
cisco	ios_xe	16.9.4c	cpe:2.3:o:cisco:ios_xe:16.9.4c:::::::*
cisco	ios_xe	16.9.5	cpe:2.3:o:cisco:ios_xe:16.9.5:::::::*
cisco	ios_xe	16.9.5f	cpe:2.3:o:cisco:ios_xe:16.9.5f:::::::*
cisco	ios_xe	16.9.6	cpe:2.3:o:cisco:ios_xe:16.9.6:::::::*
cisco	ios_xe	16.9.7	cpe:2.3:o:cisco:ios_xe:16.9.7:::::::*
cisco	ios_xe	16.10.1	cpe:2.3:o:cisco:ios_xe:16.10.1:::::::*
cisco	ios_xe	16.10.1a	cpe:2.3:o:cisco:ios_xe:16.10.1a:::::::*
cisco	ios_xe	16.10.1b	cpe:2.3:o:cisco:ios_xe:16.10.1b:::::::*
cisco	ios_xe	16.10.1c	cpe:2.3:o:cisco:ios_xe:16.10.1c:::::::*
cisco	ios_xe	16.10.1d	cpe:2.3:o:cisco:ios_xe:16.10.1d:::::::*
cisco	ios_xe	16.10.1e	cpe:2.3:o:cisco:ios_xe:16.10.1e:::::::*
cisco	ios_xe	16.10.1f	cpe:2.3:o:cisco:ios_xe:16.10.1f:::::::*
cisco	ios_xe	16.10.1g	cpe:2.3:o:cisco:ios_xe:16.10.1g:::::::*
cisco	ios_xe	16.10.1s	cpe:2.3:o:cisco:ios_xe:16.10.1s:::::::*
cisco	ios_xe	16.10.2	cpe:2.3:o:cisco:ios_xe:16.10.2:::::::*
cisco	ios_xe	16.10.3	cpe:2.3:o:cisco:ios_xe:16.10.3:::::::*

References for CVE-2021-1619

URL	Tags
https://tools.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-aaa-Yx47ZT8Q	Vendor Advisory

URL

CVE-2021-1619 | Cisco IOS XE Software NETCONF and RESTCONF Authentication Bypass Vulnerability

Exploit prediction scoring system (EPSS) score for CVE-2021-1619

Common vulnerability scoring system (CVSS) metrics for CVE-2021-1619

Weakness enumeration for CVE-2021-1619

Affected software / configurations for CVE-2021-1619

References for CVE-2021-1619