Cisco Adaptive Security Appliance (ASA) and Firepower Threat Defense (FTD): privilege escalation 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 privilege escalation vulnerability that can allow local privilege escalation from Administrator to root.

What an attacker can do

This is a privilege escalation flaw. It lets an attacker turn limited access into full administrator control. Attackers pair it with another flaw or a malicious file: once anything of theirs runs on the device, this bug lets it take over completely.

How it is reached

Needs access to the device or a file opened on it

Access the attacker needs

An administrator account

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-pers

How urgent is it

CISA added this vulnerability to its Known Exploited Vulnerabilities catalogue on April 24, 2024, which means there is reliable evidence of attacks in the wild. US federal agencies must fix it by May 1, 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 19% 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 6.0 out of 10 (medium), as recorded in the US National Vulnerability Database.

Technical description

A vulnerability in a legacy capability that allowed for the preloading of VPN clients and plug-ins and that has been available in Cisco Adaptive Security Appliance (ASA) Software and Cisco Firepower Threat Defense (FTD) Software could allow an authenticated, local attacker to execute arbitrary code with root-level privileges. Administrator-level privileges are required to exploit this vulnerability. This vulnerability is due to improper validation of a file when it is read from system flash memory. An attacker could exploit this vulnerability by copying a crafted file to the disk0: file system of an affected device. A successful exploit could allow the attacker to execute arbitrary code on the affected device after the next reload of the device, which could alter system behavior. Because the injected code could persist across device reboots, Cisco has raised the Security Impact Rating (SIR) of this advisory from Medium to High.