Actively exploited vulnerability
Cisco IOS software: denial of service flaw under attack
CVE-2017-12231 · Cisco IOS Software Network Address Translation Denial-of-Service Vulnerability
What is affected
Cisco IOS software is found on ordinary personal computers and phones, so this is not only a problem for companies. If you use it and have not updated since the fix was released, you are exposed.
A vulnerability in the implementation of Network Address Translation (NAT) functionality in Cisco IOS could allow an unauthenticated, remote attacker to cause a denial of 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
- Update Cisco IOS software now. Open the update or "About" screen, install whatever is offered and restart the app or device, because the fix is not active until you do.
- Turn on automatic updates so the next fix arrives without you having to look for it.
- If your device is too old to receive this update, stop using the affected app for anything sensitive and plan a replacement.
Apply updates per vendor instructions.
How urgent is it
CISA added this vulnerability to its Known Exploited Vulnerabilities catalogue on March 3, 2022, which means there is reliable evidence of attacks in the wild. US federal agencies must fix it by March 24, 2022, 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 7.1% probability that this flaw will be exploited somewhere in the next 30 days. That is higher than 94% of all scored vulnerabilities.
Its CVSS severity score is 7.5 out of 10 (high), as recorded in the US National Vulnerability Database.
Technical description
A vulnerability in the implementation of Network Address Translation (NAT) functionality in Cisco IOS 12.4 through 15.6 could allow an unauthenticated, remote attacker to cause a denial of service (DoS) condition on an affected device. The vulnerability is due to the improper translation of H.323 messages that use the Registration, Admission, and Status (RAS) protocol and are sent to an affected device via IPv4 packets. An attacker could exploit this vulnerability by sending a crafted H.323 RAS packet through an affected device. A successful exploit could allow the attacker to cause the affected device to crash and reload, resulting in a DoS condition. This vulnerability affects Cisco devices that are configured to use an application layer gateway with NAT (NAT ALG) for H.323 RAS messages. By default, a NAT ALG is enabled for H.323 RAS messages. Cisco Bug IDs: CSCvc57217.