CVE-2021-1501

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

HIGH

7.5

CVSS Score

Published: April 29, 2021 at 05:31 PM UTC

Updated: August 11, 2026 at 07:33 PM UTC

2 products affected across 1 vendorAdaptive Security ApplianceSecure Firewall Threat Defense

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Severity

HIGH7.5

Exploit prediction

EPSS 1%

SSVC

No known exploit

Description

A vulnerability in the SIP inspection engine of Cisco Adaptive Security Appliance (ASA) Software and Cisco Firepower Threat Defense (FTD) Software could allow an unauthenticated, remote attacker to cause a crash and reload of an affected device, resulting in a denial of service (DoS) condition.The vulnerability is due to a crash that occurs during a hash lookup for a SIP pinhole connection. An attacker could exploit this vulnerability by sending crafted SIP traffic through an affected device. A successful exploit could allow the attacker to cause a crash and reload of the affected device.

Affected

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

Adaptive Security Appliance · Cisco

95%

9.10 ≤ v < 9.12.4.189.13 ≤ v < 9.13.1.219.14 ≤ v < 9.14.2.139.15 ≤ v < 9.15.1.159.8 ≤ v < 9.8.4.349.9 ≤ v < 9.9.2.85

Affected range stops below 9.12.4.18, so it looks safe — our inference, not a vendor statement

Affected range stops below 9.13.1.21, so it looks safe — our inference, not a vendor statement

Affected range stops below 9.14.2.13, so it looks safe — our inference, not a vendor statement

Affected range stops below 9.15.1.15, so it looks safe — our inference, not a vendor statement

Affected range stops below 9.8.4.34, so it looks safe — our inference, not a vendor statement

Affected range stops below 9.9.2.85, so it looks safe — our inference, not a vendor statement

Secure Firewall Threat Defense · Cisco

95%

6.2.2 ≤ v < 6.4.0.126.5.0 ≤ v < 6.6.46.7.0 ≤ v < 6.7.0.2

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-asa-ftd-sipdos-GGwmMerC

References (1)

Vendor Advisoryx_refsource_CISCO

Source: [email protected]

https://tools.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-asa-ftd-sipdos-GGwmMerC

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-613NVD-CWE-noinfo

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