CVE-2019-9809

Severity: high (CVSS 7.5 v3.0)
Exploited in the wild: not listed in CISA KEV
EPSS: 1.6% probability of exploitation in the next 30 days
Public exploit or detection template: yes
Published: 2019-04-26 · updated 2026-06-17
Weakness: CWE-399

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.

Affected products

Mozilla Firefox: before 66.0 — fixed in 66.0

How to fix

Upgrade to a fixed version: Mozilla Firefox 66.0. Check the vendor advisory for mitigations.

References

https://bugzilla.mozilla.org/show_bug.cgi?id=1282430
https://bugzilla.mozilla.org/show_bug.cgi?id=1523249
https://www.mozilla.org/security/advisories/mfsa2019-07/
https://bugzilla.mozilla.org/show_bug.cgi?id=1282430
https://bugzilla.mozilla.org/show_bug.cgi?id=1523249
https://www.mozilla.org/security/advisories/mfsa2019-07/

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