CVE-2021-1573

Cisco Adaptive Security Appliance Software and Firepower Threat Defense Software Web Services Denial of Service Vulnerability

HIGH

7.5

CVSS Score

Published: January 11, 2022 at 06:55 PM UTC

Updated: August 11, 2026 at 07:37 PM UTC

3 products affected across 1 vendorAdaptive Security ApplianceSecure Firewall Threat DefenseFirepower Threat Defense

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Severity

HIGH7.5

Exploit prediction

EPSS 1%

SSVC

No known exploit

Description

A vulnerability in the web services interface of Cisco Adaptive Security Appliance (ASA) Software and Cisco Firepower Threat Defense (FTD) Software could allow an unauthenticated, remote attacker to trigger a denial of service (DoS) condition. This vulnerability is due to improper input validation when parsing HTTPS requests. An attacker could exploit this vulnerability by sending a malicious HTTPS request to an affected device. A successful exploit could allow the attacker to cause the device to reload, resulting in a DoS condition.

Affected

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

Adaptive Security Appliance · Cisco

95%

v ≤ 9.7v < 6.4.0.139.13 ≤ v < 9.14.39.15 ≤ v < 9.15.1.179.16 ≤ v < 9.16.1.289.8 ≤ v < 9.8.4.409.9 ≤ v < 9.12.4.26

Affected range stops below 6.4.0.13, so it looks safe — our inference, not a vendor statement

Affected range stops below 9.12.4.26, so it looks safe — our inference, not a vendor statement

Affected range stops below 9.14.3, so it looks safe — our inference, not a vendor statement

Affected range stops below 9.15.1.17, so it looks safe — our inference, not a vendor statement

Affected range stops below 9.16.1.28, so it looks safe — our inference, not a vendor statement

Affected range stops below 9.8.4.40, so it looks safe — our inference, not a vendor statement

Secure Firewall Threat Defense · Cisco

95%

v ≤ 6.2.26.2.3 ≤ v < 6.4.0.136.5.0 ≤ v < 6.6.56.7.0 ≤ v < 6.7.0.37.0.0

Firepower Threat Defense · Cisco

60%

v < 6.6.5

Affected range stops below 6.4.0.13, so it looks safe — our inference, not a vendor statement

Affected range stops below 6.6.5, so it looks safe — our inference, not a vendor statement

Affected range stops below 6.7.0.3, so it looks safe — our inference, not a vendor statement

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-asafdt-webvpn-dos-KSqJAKPA

References (1)

Vendor Advisoryx_refsource_CISCO

Source: [email protected]

https://tools.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-asafdt-webvpn-dos-KSqJAKPA

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-121CWE-787

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