Cisco Adaptive Security Appliance Software Release 9.16.1 and Cisco Firepower Threat Defense Software Release 7.0.0 IPsec Denial of Service Vulnerability

published 2021-07-16 5 y ago modified 2026-08-11 2 mo ago also EUVD-2021-6889

cvss: 7.7; version 3.1, CNA
cisa kev: Not listed; not in CISA's catalog
epss: 1.2%; EPSS 1.2% chance of exploitation in 30 days, percentile 68%
public exploits: 0; none known

A vulnerability in the software cryptography module of Cisco Adaptive Security Appliance (ASA) Software and Cisco Firepower Threat Defense (FTD) Software could allow an authenticated, remote attacker or an unauthenticated attacker in a man-in-the-middle position to cause an unexpected reload of the device that results in a denial of service (DoS) condition. The vulnerability is due to a logic error in how the software cryptography module handles specific types of decryption errors. An attacker could exploit this vulnerability by sending malicious packets over an established IPsec connection. A successful exploit could cause the device to crash, forcing it to reload. Important: Successful exploitation of this vulnerability would not cause a compromise of any encrypted data. Note: This vulnerability affects only Cisco ASA Software Release 9.16.1 and Cisco FTD Software Release 7.0.0.

CISA SSVC

Exploitation: none
Automatable: no
Technical impact: partial
Assessed: 2 y ago (2024-11-07)

Exploit prediction

1.20% chance of exploitation in the next 30 days, higher than 68% of all scored CVEs (FIRST EPSS, 2026-11-08).

CVSS scores

assigned by	version	score	vector
CNA	3.1	7.7	CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:C/C:N/I:N/A:H
NVD	3.1	7.7	CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:C/C:N/I:N/A:H
NVD	2.0	6.8	AV:N/AC:L/Au:S/C:N/I:N/A:C

Affected products

Cisco Cisco Adaptive Security Appliance (ASA) Software

Classification

Weakness

CWE-617 Reachable Assertion

References

tools.cisco.com /security/center/content/CiscoSecurityAdvisory/cisco-sa-asa-ftd-ipsec-dos-TFKQbgWC
vendor-advisory

Sources

CVE List CVE-2021-1422
NVD CVE-2021-1422

Fencer Vulns keeps one entry per vulnerability: the CVE id wins, then GHSA, and records that alias each other are merged, except that two CVEs always keep separate entries. The same data is available as JSON.

Summary