What is CVE-2021-1501?

CVE-2021-1501 is a high-severity vulnerability in Cisco Adaptive Security Appliance Software, classified under Insufficient Session Expiration. CVSS score: 8.6/10. Published 2021-04-29.

How severe is CVE-2021-1501?

High severity. CVSS v3 base score is 8.6 out of 10.

Vulnerability in Cisco Adaptive Security Appliance Software

CVE-2021-1501

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.

Published 2021-04-29 · last modified 2026-08-11.

CVSS v3 metric

CVSS v3 base score 8.6 (High). Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:N/I:N/A:H.

EPSS exploit prediction

EPSS: 0.013 (70.3th percentile), scored 2026-10-01.

Low probability of exploitation in the next 30 days, but still tracked. 70th percentile — 70.3% of CVEs in the catalogue have a lower EPSS than this one. How to read EPSS.

EPSS over last 30 days · oldest: 0.013 · newest: 0.013 · change: 0.000

Affected products

Weakness classification (CWE)

CWE-613 — Insufficient Session Expiration

References

tools.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-asa-ftd-… (vendor-advisory, Vendor Advisory)

Frequently asked questions

What is CVE-2021-1501?: CVE-2021-1501 is a high-severity vulnerability in Cisco Adaptive Security Appliance Software, classified under Insufficient Session Expiration. CVSS score: 8.6/10. Published 2021-04-29.
How severe is CVE-2021-1501?: High severity. CVSS v3 base score is 8.6 out of 10.