CVE-2019-9809 Denial of service in Firefox

What is CVE-2019-9809?

CVE-2019-9809 is a high-severity denial of service vulnerability in Mozilla Firefox, published on 26 Apr 2019. An attacker can exploit it over the internet without logging in, with no action from the victim.

Official description

If the source for resources on a page is through an FTP connection, it is possible to trigger a series of modal alert messages for these resources through invalid credentials or locations. These messages cannot be immediately dismissed, allowing for a denial of service (DOS) attack. This vulnerability affects Firefox < 66.

Weakness: CWE-399

Which versions are affected by CVE-2019-9809?

It affects 1 product.

Products include Mozilla Firefox.

How do I fix CVE-2019-9809?

Upgrade to a fixed version.

Upgrade, then put limits on request size, rate and nesting depth so one client cannot exhaust the service. More about Denial of service.

Is CVE-2019-9809 being exploited?

There is no known exploitation of CVE-2019-9809 in the wild and no public exploit code.

Other vulnerabilities in Mozilla Firefox

• CVE-2019-11708 Mozilla Firefox and Thunderbird Sandbox Escape Exploited Critical 10.0
• CVE-2010-3765 Mozilla Multiple Products Remote Code Execution Exploited Critical 9.8
• CVE-2022-26486 Mozilla Firefox Use-After-Free Exploited Critical 9.6
• CVE-2022-26485 Mozilla Firefox Use-After-Free Exploited High 8.8
• CVE-2019-11707 Mozilla Firefox and Thunderbird Type Confusion Exploited High 8.8

All Mozilla Firefox vulnerabilities

Sources

• CVE record
• NVD
• OSV
• GitHub advisory
• How this page is made

Also known as GHSA-mhpj-9q2x-79mx, UBUNTU-CVE-2019-9809.