CVE-2019-12677: A vulnerability in the Secure Sockets Layer (SSL) VPN feature of Cisco Adaptive Security Appliance (ASA) Software could allow an authenticated, remote...

Description

A vulnerability in the Secure Sockets Layer (SSL) VPN feature of Cisco Adaptive Security Appliance (ASA) Software could allow an authenticated, remote attacker to cause a denial of service (DoS) condition that prevents the creation of new SSL/Transport Layer Security (TLS) connections to an affected device. The vulnerability is due to incorrect handling of Base64-encoded strings. An attacker could exploit this vulnerability by opening many SSL VPN sessions to an affected device. The attacker would need to have valid user credentials on the affected device to exploit this vulnerability. A successful exploit could allow the attacker to overwrite a special system memory location, which will eventually result in memory allocation errors for new SSL/TLS sessions to the device, preventing successful establishment of these sessions. A reload of the device is required to recover from this condition. Established SSL/TLS connections to the device and SSL/TLS connections through the device are not affected. Note: Although this vulnerability is in the SSL VPN feature, successful exploitation of this vulnerability would affect all new SSL/TLS sessions to the device, including management sessions.

Metrics

CVSS 3.1

6.5/10

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

EPSS Probability

1.53%

71.5th percentile

Probability of exploitation in the next 30 days. Learn more

Weakness Enumeration

Affected Software

Vendor	Product	Versions
Cisco	Adaptive Security Appliance Software	>= 9.3, < 9.3.3.9
Cisco	Adaptive Security Appliance Software	< 9.1.7.4
Cisco	Adaptive Security Appliance Software	>= 9.2, < 9.2.4.8
Cisco	Adaptive Security Appliance Software	>= 9.4, < 9.4.2.11
Cisco	Adaptive Security Appliance Software	>= 9.5, < 9.5.2.5
Cisco	Adaptive Security Appliance Software	>= 9.6, < 9.6.2

References

Timeline

Published: Oct 2, 2019
Last Modified: Jun 17, 2026
Status: Modified

Frequently Asked Questions

What is CVE-2019-12677?

A vulnerability in the Secure Sockets Layer (SSL) VPN feature of Cisco Adaptive Security Appliance (ASA) Software could allow an authenticated, remote attacker to cause a denial of service (DoS) condition that prevents the creation of new SSL/Transport Layer Security (TLS) connections to an affected device. The vulnerability is due to incorrect handling of Base64-encoded strings. An attacker could exploit this vulnerability by opening many SSL VPN sessions to an affected device. The attacker would need to have valid user credentials on the affected device to exploit this vulnerability. A successful exploit could allow the attacker to overwrite a special system memory location, which will eventually result in memory allocation errors for new SSL/TLS sessions to the device, preventing successful establishment of these sessions. A reload of the device is required to recover from this condition. Established SSL/TLS connections to the device and SSL/TLS connections through the device are not affected. Note: Although this vulnerability is in the SSL VPN feature, successful exploitation of this vulnerability would affect all new SSL/TLS sessions to the device, including management sessions.

How severe is CVE-2019-12677?

CVE-2019-12677 has a CVSS score of 6.5/10 (MEDIUM severity). The EPSS model estimates a 1.53% probability of exploitation in the next 30 days.

How do I fix CVE-2019-12677?

Check the vendor references and advisories linked above for patched versions and mitigation guidance. You can also run a Strix scan to test if your systems are affected.