CVE•Published 2021-04-29•Modified 2026-08-11•1 article on news•5 live references•NVD data

CVE-2021-1501Cisco · Secure_firewall_threat_defense

Vulnerability data via NVD (ingested)

CVSS v3.1

8.6

HIGH

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

EPSS percentile

Exploit Prediction Scoring System · top 31% of all CVEs

Weaknesses (CWE)

CWE-613Insufficient Session Expiration

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.

Timeline

Published 2021-04-29

Modified 2026-08-11

External references

NVD MITRE Exploit-DB GitHub PoC VulnCheck

Search for exposed instances

Shodan + Censys queries derived from NVD's CPE data. The vuln tag catches assets Shodan has explicitly linked to this CVE; the product / banner fingerprints find exposed instances even when the vuln tag was never applied (which is common).

Shodan · vuln tag0 hosts

vuln:CVE-2021-1501

Hosts Shodan has explicitly fingerprinted as vulnerable.

Shodan · product

product:"Cisco Secure Firewall Threat Defense"

All exposed Cisco Secure Firewall Threat Defense instances — cross-reference with the CVE's affected-version range.

Shodan · banner/body mention

http.html:"Secure Firewall Threat Defense"

HTTP body or banner mentions "Secure Firewall Threat Defense" — catches deploys Shodan didn't identify as a product.

More intel sources (5)

Shodan report

vuln:CVE-2021-1501