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CVE-2021-1446

Cisco IOS XE Software DNS NAT Protocol Application Layer Gateway Denial of Service Vulnerability

HIGH

7.5

CVSS Score

Published: March 24, 2021 at 08:06 PM UTC

Updated: June 17, 2026 at 03:31 AM UTC

1 product affected across 1 vendorIOS Xe

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Severity

HIGH7.5

Exploit prediction

EPSS 2%

SSVC

No known exploit

Description

A vulnerability in the DNS application layer gateway (ALG) functionality used by Network Address Translation (NAT) in Cisco IOS XE Software could allow an unauthenticated, remote attacker to cause an affected device to reload. The vulnerability is due to a logic error that occurs when an affected device inspects certain DNS packets. An attacker could exploit this vulnerability by sending crafted DNS packets through an affected device that is performing NAT for DNS packets. A successful exploit could allow an attacker to cause the device to reload, resulting in a denial of service (DoS) condition on an affected device. The vulnerability can be exploited only by traffic that is sent through an affected device via IPv4 packets. The vulnerability cannot be exploited via IPv6 traffic.

Affected

Our own answer: ranges merged, affected separated from platform-only, with confidence and review flags.

IOS Xe · Cisco

95%

16.1.1 16.1.2 16.1.3 16.10.1 16.10.1a 16.10.1b 16.10.1c 16.10.1d 16.10.1e 16.10.1f 16.10.1g 16.10.1s 16.10.2 16.10.3 16.11.1 16.11.1a 16.11.1b 16.11.1c 16.11.1s 16.11.2 16.12.1 16.12.1a 16.12.1c 16.12.1s 16.12.1t 16.12.1w 16.12.1x 16.12.1y 16.12.1z 16.12.1z1 16.12.1za 16.12.2 16.12.2a 16.12.2s 16.12.2t 16.12.3 16.12.3a 16.12.3s 16.12.4 16.12.4a 16.2.1 16.2.2 16.3.1 16.3.10 16.3.11 16.3.1a 16.3.2 16.3.3 16.3.4 16.3.5 16.3.5b 16.3.6 16.3.7 16.3.8 16.3.9 16.4.1 16.4.2 16.4.3 16.5.1 16.5.1a 16.5.1b 16.5.2 16.5.3 16.6.1 16.6.2 16.6.3 16.6.4 16.6.4a 16.6.4s 16.6.5 16.6.5a 16.6.5b 16.6.6 16.6.7 16.6.7a 16.6.8 16.7.1 16.7.1a 16.7.1b 16.7.2 16.7.3 16.7.4 16.8.1 16.8.1a 16.8.1b 16.8.1c 16.8.1d 16.8.1e 16.8.1s 16.8.2 16.8.3 16.9.1 16.9.1a 16.9.1b 16.9.1c 16.9.1d 16.9.1s 16.9.2 16.9.2a 16.9.2s 16.9.3 16.9.3a 16.9.3h 16.9.3s 16.9.4 16.9.4c 16.9.5 16.9.5f 16.9.6 17.1.1 17.1.1a 17.1.1s 17.1.1t 17.1.2 17.2.1 17.2.1a 17.2.1r 17.2.1v 17.2.2 17.2.3 17.3.1 17.3.1a 17.3.1w 3.10.0s 3.10.10s 3.10.1s 3.10.1xbs 3.10.1xcs 3.10.2as 3.10.2s 3.10.2ts 3.10.3s 3.10.4s 3.10.5s 3.10.6s 3.10.7s 3.10.8as 3.10.8s 3.10.9s 3.11.0s 3.11.1s 3.11.2s 3.11.3s 3.11.4s 3.12.0as 3.12.0s 3.12.1s 3.12.2s 3.12.3s 3.12.4s 3.13.0as 3.13.0s 3.13.10s 3.13.1s 3.13.2as 3.13.2s 3.13.3s 3.13.4s 3.13.5as 3.13.5s 3.13.6as 3.13.6bs 3.13.6s 3.13.7as 3.13.7s 3.13.8s 3.13.9s 3.14.0s 3.14.1s 3.14.2s 3.14.3s 3.14.4s 3.15.0s 3.15.1cs 3.15.1s 3.15.1xbs 3.15.2s 3.15.2xbs 3.15.3s 3.15.4s 3.16.0as 3.16.0bs 3.16.0cs 3.16.0s 3.16.10as 3.16.10s 3.16.1as 3.16.1s 3.16.2as 3.16.2bs 3.16.2s 3.16.3as 3.16.3s 3.16.4as 3.16.4bs 3.16.4cs 3.16.4ds 3.16.4es 3.16.4gs 3.16.4s 3.16.5as 3.16.5bs 3.16.5s 3.16.6bs 3.16.6s 3.16.7as 3.16.7bs 3.16.7s 3.16.8s 3.16.9s 3.17.0s 3.17.1as 3.17.1s 3.17.2s 3.17.3s 3.17.4s 3.18.0as 3.18.0s 3.18.0sp 3.18.1asp 3.18.1bsp 3.18.1csp 3.18.1gsp 3.18.1hsp 3.18.1isp 3.18.1s 3.18.1sp 3.18.2asp 3.18.2s 3.18.2sp 3.18.3asp 3.18.3bsp 3.18.3s 3.18.3sp 3.18.4s 3.18.4sp 3.18.5sp 3.18.6sp 3.18.7sp 3.18.8asp 3.18.8sp 3.7.0bs 3.7.0s 3.7.0xas 3.7.0xbs 3.7.1as 3.7.1s 3.7.2s 3.7.2ts 3.7.3s 3.7.4as 3.7.4s 3.7.5s 3.7.6s 3.7.7s 3.7.8s 3.8.0s 3.8.1s 3.8.2s 3.9.0as 3.9.0s 3.9.0xas 3.9.1as 3.9.1s 3.9.2s

Remediation

No guide yet

No remediation guidance has been written for this CVE yet. What the record does show:

Patch and advisory references

https://tools.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-alg-dos-hbBS7SZE

References (1)

Vendor Advisoryx_refsource_CISCO

Source: [email protected]

https://tools.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-alg-dos-hbBS7SZE

SSVC — Action Prioritization

SSVCNo known exploitAutomatablePartial impact

SSVC signals action urgency (what to patch first), separate from CVSS which measures severity.

CVSS

7.5HIGH[email protected]

Attack Vector: NETWORK
Complexity: LOW
Privileges: NONE
User Interaction: NONE
Scope: UNCHANGED
Confidentiality: NONE
Integrity: NONE
Availability: HIGH

Vector?

Quick Info

StatusMODIFIED

CWE

CWE-754

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