CVE-2024-20353Cisco ASA and FTD Denial of Service Vulnerability
CVE-2024-20353 is a infinite loop in Cisco Adaptive Security Appliance (ASA) and Firepower Threat Defense (FTD), rated high (8.6 on CVSS 3.1).
Why this priority: Exploited in the wild: listed in CISA's KEV catalog.
Published · Updated · NVD status: Analyzed
What it is
Crafted input sends the software into a loop it never leaves.
How it is reached
An attacker can exploit it over the network, without an account, and nobody has to click anything.
What an attacker gains
A successful attack can take it offline. In practice, this kind of flaw lets an attacker exhaust CPU, memory or connections until the service stops answering. The damage can spread past the vulnerable component into others.
Is it being exploited?
CISA added it to the Known Exploited Vulnerabilities catalog on 2024-04-24: it is being exploited in the wild. It can be exploited automatically, at scale. EPSS estimates a 70% chance of exploitation activity in the next 30 days, higher than 99% of scored CVEs.
What to do
- Treat it as urgent: it is on CISA's KEV list. CISA's deadline for US federal agencies: 2024-05-01.
- Upgrade Cisco Adaptive Security Appliance (ASA) and Firepower Threat Defense (FTD) to 9.14.4.23 or later.
- Until it is patched, keep it off the internet or behind a VPN, allowlist or authenticating proxy.
- Check exposed instances for signs of compromise, not only for the version.
Description from NVD
A vulnerability in the management and VPN web servers for Cisco Adaptive Security Appliance (ASA) Software and Cisco Firepower Threat Defense (FTD) Software could allow an unauthenticated, remote attacker to cause the device to reload unexpectedly, resulting in a denial of service (DoS) condition. This vulnerability is due to incomplete error checking when parsing an HTTP header. An attacker could exploit this vulnerability by sending a crafted HTTP request to a targeted web server on a device. A successful exploit could allow the attacker to cause a DoS condition when the device reloads.
What this means for your architecture.
A CVE names a product. Whether it matters depends on where that product sits in your systems: what reaches it, which trust boundary it guards and what it can reach once compromised. Veriom maps your components, their relationships and your trust boundaries from your code, cloud and delivery evidence, so you can see where a component like this sits. The radar itself does not look at your systems.
Components it touches
- Network edge devices: VPNs, firewalls, routers and gateways. They sit between the internet and internal networks, so a flaw in one is often the first step into everything behind it.
- Operating systems on servers, workstations or devices. Everything on the host inherits the flaw.
- Public entry points and shared services that must stay up. The flaw sits between untrusted traffic and shared capacity.
Trust boundaries in play
- Internet-facing entry points. No account is needed. Any instance reachable from outside your perimeter, through a load balancer, gateway, VPN or exposed admin port, is in scope.
- Isolation between components. The impact crosses out of the vulnerable component into others it should be isolated from.
- Between untrusted traffic and shared capacity. An attacker who crosses it can exhaust CPU, memory or connections until the service stops answering.
Questions to answer about your own systems
- Where does Cisco Adaptive Security Appliance (ASA) and Firepower Threat Defense (FTD) run in your systems, and at which version?
- Which of those instances can be reached from the internet or partner networks?
- What can it reach once compromised: which data stores, secrets and services?
Read more
Advisories
Exploits and proofs of concept
Sources
- CVE records and CVSS scores from the NVD CVE API. This product uses the NVD API but is not endorsed or certified by the NVD.
- Exploitation status from CISA’s Known Exploited Vulnerabilities catalog.
- Exploit likelihood from FIRST’s Exploit Prediction Scoring System (EPSS), refreshed daily.
- Explanations are written by Veriom from fixed templates over each record’s data, not by a person reviewing each CVE. Descriptions are quoted from the records as published.