CVE-2020-3555

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

HIGH

7.5

CVSS Score

Published: October 21, 2020 at 06:41 PM UTC

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

2 products affected across 1 vendorAdaptive Security ApplianceSecure Firewall Threat Defense

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Severity

HIGH7.5

Exploit prediction

EPSS 2%

SSVC

No known exploit

Description

A vulnerability in the SIP inspection process 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 watchdog timeout and crash during the cleanup of threads that are associated with a SIP connection that is being deleted from the connection list. An attacker could exploit this vulnerability by sending a high rate of crafted SIP traffic through an affected device. A successful exploit could allow the attacker to cause a watchdog timeout and crash, resulting in 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%

v < 9.6.4.439.10.0 ≤ v < 9.10.1.439.12.0 ≤ v < 9.12.4.29.13.0 ≤ v < 9.13.1.139.14.0 ≤ v < 9.14.1.199.7.0 ≤ v < 9.8.4.249.9.0 ≤ v < 9.9.2.80

Affected range stops below 9.10.1.43, so it looks safe — our inference, not a vendor statement

Affected range stops below 9.12.4.2, so it looks safe — our inference, not a vendor statement

Affected range stops below 9.13.1.13, so it looks safe — our inference, not a vendor statement

Affected range stops below 9.14.1.19, so it looks safe — our inference, not a vendor statement

Affected range stops below 9.6.4.43, so it looks safe — our inference, not a vendor statement

Affected range stops below 9.8.4.24, so it looks safe — our inference, not a vendor statement

Affected range stops below 9.9.2.80, so it looks safe — our inference, not a vendor statement

Secure Firewall Threat Defense · Cisco

95%

v ≤ 6.2.26.3.0 ≤ v < 6.3.0.66.4.0 ≤ v < 6.4.0.106.5.0 ≤ v < 6.5.0.56.6.0

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-asaftd-sipdos-3DGvdjvg

References (1)

Vendor Advisoryx_refsource_CISCO

Source: [email protected]

https://tools.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-asaftd-sipdos-3DGvdjvg

SSVC — Action Prioritization

SSVCNo known exploitNot automatablePartial 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-404

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