How severe is CVE-2021-40117?

CVE-2021-40117 has a CVSS 3.x base score of 8.6, rated high severity. It is exploitable over network with low attack complexity, requires no privileges and no user interaction. Impact on confidentiality is none, integrity none, and availability high.

Is CVE-2021-40117 being actively exploited?

It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 1% (71st percentile), an estimate of the probability of exploitation in the next 30 days.

What products are affected by CVE-2021-40117?

CVE-2021-40117 primarily affects Cisco Adaptive Security Appliance. In total, 19 product configurations (CPEs) are listed as vulnerable; see the affected-products list for the exact versions.

How do I fix CVE-2021-40117?

Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround. Given its high severity, prioritise patching exposed systems.

When was CVE-2021-40117 published?

CVE-2021-40117 was published on 2021-10-27 and last updated on 2026-06-17.

CVE-2021-40117

CVE-2021-40117 is a high-severity vulnerability in Cisco Adaptive Security Appliance with a CVSS 3.x base score of 8.6. It is not currently listed as actively exploited by CISA, and its EPSS exploit-prediction score is low. The underlying weakness is classified as CWE-400.

Key facts

Severity: High (CVSS 3.x base score 8.6)
CVSS v2: 7.8
EPSS exploit prediction: 1% (71st percentile)
Actively exploited: Not listed in CISA KEV
Weakness: CWE-400
Affected product: Cisco Adaptive Security Appliance
Published: 2021-10-27
Last modified: 2026-06-17

Description

A vulnerability in SSL/TLS message handler for Cisco Adaptive Security Appliance (ASA) Software and Cisco Firepower Threat Defense (FTD) Software could allow an unauthenticated, remote attacker to cause a denial of service (DoS) condition on an affected device. This vulnerability exists because incoming SSL/TLS packets are not properly processed. An attacker could exploit this vulnerability by sending a crafted SSL/TLS packet to an affected device. A successful exploit could allow the attacker to cause the affected device to reload, resulting in a DoS condition.

Frequently asked questions

What is CVE-2021-40117?: A vulnerability in SSL/TLS message handler for Cisco Adaptive Security Appliance (ASA) Software and Cisco Firepower Threat Defense (FTD) Software could allow an unauthenticated, remote attacker to cause a denial of service (DoS) condition on an affected device. This vulnerability exists because incoming SSL/TLS packets are not properly processed. An attacker could exploit this vulnerability by sending a crafted SSL/TLS packet to an affected device. A successful exploit could allow the attacker to cause the affected device to reload, resulting in a DoS condition.
How severe is CVE-2021-40117?: CVE-2021-40117 has a CVSS 3.x base score of 8.6, rated high severity. It is exploitable over network with low attack complexity, requires no privileges and no user interaction. Impact on confidentiality is none, integrity none, and availability high.
Is CVE-2021-40117 being actively exploited?: It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 1% (71st percentile), an estimate of the probability of exploitation in the next 30 days.
What products are affected by CVE-2021-40117?: CVE-2021-40117 primarily affects Cisco Adaptive Security Appliance. In total, 19 product configurations (CPEs) are listed as vulnerable; see the affected-products list for the exact versions.
How do I fix CVE-2021-40117?: Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround. Given its high severity, prioritise patching exposed systems.
When was CVE-2021-40117 published?: CVE-2021-40117 was published on 2021-10-27 and last updated on 2026-06-17.

References

https://tools.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-asaftd-dos-4ygzLKU9

Affected products (19)

cpe:2.3:a:cisco:adaptive_security_appliance:*:*:*:*:*:*:*:*
cpe:2.3:a:cisco:firepower_threat_defense:*:*:*:*:*:*:*:*
cpe:2.3:o:cisco:adaptive_security_appliance_software:*:*:*:*:*:*:*:*
cpe:2.3:o:cisco:asa_5512-x_firmware:009.009\(002.085\):*:*:*:*:*:*:*
cpe:2.3:o:cisco:asa_5512-x_firmware:009.014\(002.106\):*:*:*:*:*:*:*
cpe:2.3:o:cisco:asa_5505_firmware:009.009\(002.085\):*:*:*:*:*:*:*
cpe:2.3:o:cisco:asa_5505_firmware:009.014\(002.106\):*:*:*:*:*:*:*
cpe:2.3:o:cisco:asa_5515-x_firmware:009.009\(002.085\):*:*:*:*:*:*:*
cpe:2.3:o:cisco:asa_5515-x_firmware:009.014\(002.106\):*:*:*:*:*:*:*
cpe:2.3:o:cisco:asa_5525-x_firmware:009.009\(002.085\):*:*:*:*:*:*:*
cpe:2.3:o:cisco:asa_5525-x_firmware:009.014\(002.106\):*:*:*:*:*:*:*
cpe:2.3:o:cisco:asa_5545-x_firmware:009.009\(002.085\):*:*:*:*:*:*:*
cpe:2.3:o:cisco:asa_5545-x_firmware:009.014\(002.106\):*:*:*:*:*:*:*
cpe:2.3:o:cisco:asa_5555-x_firmware:009.009\(002.085\):*:*:*:*:*:*:*
cpe:2.3:o:cisco:asa_5555-x_firmware:009.014\(002.106\):*:*:*:*:*:*:*
cpe:2.3:o:cisco:asa_5580_firmware:009.009\(002.085\):*:*:*:*:*:*:*
cpe:2.3:o:cisco:asa_5580_firmware:009.014\(002.106\):*:*:*:*:*:*:*
cpe:2.3:o:cisco:asa_5585-x_firmware:009.009\(002.085\):*:*:*:*:*:*:*
cpe:2.3:o:cisco:asa_5585-x_firmware:009.014\(002.106\):*:*:*:*:*:*:*

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