Cisco Adaptive Security Appliance (ASA) and Firepower Threat Defense (FTD): denial of service flaw under attack

What is affected

Cisco Adaptive Security Appliance (ASA) and Firepower Threat Defense (FTD) is mostly run by companies, schools and public bodies, not on home computers. You are unlikely to have it yourself, but organisations that hold your data may. Breaches that start with flaws like this one are how personal data ends up leaked.

Cisco Adaptive Security Appliance (ASA) and Firepower Threat Defense (FTD) contain a missing release of resource after effective lifetime vulnerability that could allow an unauthenticated, remote attacker to cause a denial-of-service (DoS) of the RAVPN service.

What an attacker can do

This is a denial of service flaw. It lets an attacker crash the product or make it unavailable to the people who rely on it.

How it is reached

Over the internet or network

Access the attacker needs

No account needed

Does the victim have to do something?

No, works without the victim doing anything

What to do

1. At home: nothing to install. Keep your own devices updated and use a different password for every service, so that a breach at one organisation does not open your other accounts.
2. If you administer Cisco Adaptive Security Appliance (ASA) and Firepower Threat Defense (FTD) at work: apply the vendor's fix or mitigation now and review logs for signs of compromise, because the flaw was being exploited before it was listed.
3. If the product is past its support date and no fix exists, take it off the internet or retire it.

Apply mitigations per vendor instructions or discontinue use of the product if mitigations are unavailable.

Vendor advisories and fixes

• sec.cloudapps.cisco.comsec.cloudapps.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-asaftd-bf-d

How urgent is it

CISA added this vulnerability to its Known Exploited Vulnerabilities catalogue on October 24, 2024, which means there is reliable evidence of attacks in the wild. US federal agencies must fix it by November 14, 2024, a deadline that has already passed. That deadline does not bind anyone else, but it shows how seriously the agency rates it.

The EPSS model estimates a 16% probability that this flaw will be exploited somewhere in the next 30 days. That is higher than 97% of all scored vulnerabilities.

Its CVSS severity score is 5.8 out of 10 (medium), as recorded in the US National Vulnerability Database.

Technical description

A vulnerability in the Remote Access VPN (RAVPN) service of 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) of the RAVPN service. This vulnerability is due to resource exhaustion. An attacker could exploit this vulnerability by sending a large number of VPN authentication requests to an affected device. A successful exploit could allow the attacker to exhaust resources, resulting in a DoS of the RAVPN service on the affected device. Depending on the impact of the attack, a reload of the device may be required to restore the RAVPN service. Services that are not related to VPN are not affected. Cisco Talos discussed these attacks in the blog post Large-scale brute-force activity targeting VPNs, SSH services with commonly used login credentials.