CVE-2019-12677

What it is

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.

At a glance

Exploitability

Can be exploited over the network with a low-privilege account. High risk of service disruption.

Exploit odds

1.5% chance of exploitation in the next 30 days (EPSS).

Fix

A patch, advisory or fixed version is referenced. Upgrade or apply it.

Timeline

1. 2019-10-02 19:15 UTC PublishedDisclosed publicly on CVE.org and NVD
2. 2026-06-17 02:15 UTC Last updatedMost recent change to the record

Why it ranks here

• Exploited in the wild: no, CISA does not list it.
• Exploit odds: 1.5% in the next 30 days (EPSS).
• Severity: 6.5 MEDIUM (CVSS).
• Fix: a patch or advisory is linked.

Details

Published

2019-10-02 19:15 UTC

Last modified

2026-06-17 02:15 UTC

Exploit probability

1.5% · EPSS, next 30 days

Weakness

CWE-172

Record status

Modified

Affected

• Cisco Adaptive Security Appliance Software < 9.3.3.9
• Cisco Adaptive Security Appliance Software < 9.1.7.4
• Cisco Adaptive Security Appliance Software < 9.2.4.8
• Cisco Adaptive Security Appliance Software < 9.4.2.11
• Cisco Adaptive Security Appliance Software < 9.5.2.5
• Cisco Adaptive Security Appliance Software < 9.6.2

Attack profile CVSS 3.1 · 6.5

Attack vector

Network

Complexity

Low

Privileges needed

Low

User interaction

None

Scope

Unchanged

Confidentiality

None

Integrity

None

Availability

High

Is it in your code?

Hand this to your coding agent. It searches your project for the affected products and checks versions. Nothing leaves your machine.

Read https://cve-list.com/agent/cve/CVE-2019-12677.md and follow it. Check whether this project is affected by CVE-2019-12677. Read only. Don't change anything and don't upload my code. Tell me yes, no or not sure, with the file as proof.

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