Vulnerability in Mozilla Firefox

CVE-2019-11730

A vulnerability exists where if a user opens a locally saved HTML file, this file can use file: URIs to access other files in the same directory or sub-directories if the names are known or guessed. The Fetch API can then be used to read the contents of any files stored in these directories and they may uploaded to a server. It was demonstrated that in combination with a popular Android messaging app, if a malicious HTML attachment is sent to a user and they opened that attachment in Firefox, due to that app's predictable pattern for locally-saved file names, it is possible to read attachments the victim received from other correspondents. This vulnerability affects Firefox ESR < 60.8, Firefox < 68, and Thunderbird < 60.8.

EPSS: 0.203 (97.2th percentile) — read the EPSS interpretation.

CVSS v3 metric

CVSS v3 base score 6.5 (Medium). Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:N/A:N.

Affected products

Public proof-of-concept exploits

References

Frequently asked questions

What is CVE-2019-11730?
CVE-2019-11730 is a medium-severity vulnerability in Mozilla Firefox. CVSS score: 6.5/10. Published 2019-07-23.
How severe is CVE-2019-11730?
Medium severity. CVSS v3 base score is 6.5 out of 10.
Is CVE-2019-11730 known to be exploited?
19 public proof-of-concept repositories are indexed. Not currently listed in the CISA KEV catalog.