Actively exploited vulnerability
Mozilla Firefox and Thunderbird: memory corruption flaw under attack
CVE-2019-11707 · Mozilla Firefox and Thunderbird Type Confusion Vulnerability
What is affected
Mozilla Firefox and Thunderbird 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.
Mozilla Firefox and Thunderbird contain a type confusion vulnerability that can occur when manipulating JavaScript objects due to issues in Array.pop, allowing for an exploitable crash.
What an attacker can do
This is a memory corruption flaw. It lets an attacker corrupt the program's memory by feeding it specially crafted content: a web page, a file or a network message. The result ranges from a crash to the attacker running their own code.
- How it is reached
- Over the internet or network
- Access the attacker needs
- No account needed
- Does the victim have to do something?
- Yes, the victim must open or click something
What to do
- Update Mozilla Firefox and Thunderbird 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 May 23, 2022, which means there is reliable evidence of attacks in the wild. US federal agencies must fix it by June 13, 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 38% probability that this flaw will be exploited somewhere in the next 30 days. That is higher than 99% of all scored vulnerabilities.
Its CVSS severity score is 8.8 out of 10 (high), as recorded in the US National Vulnerability Database.
Technical description
A type confusion vulnerability can occur when manipulating JavaScript objects due to issues in Array.pop. This can allow for an exploitable crash. We are aware of targeted attacks in the wild abusing this flaw. This vulnerability affects Firefox ESR < 60.7.1, Firefox < 67.0.3, and Thunderbird < 60.7.2.