What is CVE-2018-12402?

CVE-2018-12402 is a medium-severity vulnerability in Mozilla Firefox, classified under Origin Validation Error. CVSS score: 6.5/10. Published 2019-02-28.

How severe is CVE-2018-12402?

Medium severity. CVSS v3 base score is 6.5 out of 10.

Vulnerability in Mozilla Firefox

CVE-2018-12402

The internal WebBrowserPersist code does not use correct origin context for a resource being saved. This manifests when sub-resources are loaded as part of "Save Page As..." functionality. For example, a malicious page could recover a visitor's Windows username and NTLM hash by including resources otherwise unreachable to the malicious page, if they can convince the visitor to save the complete web page. Similarly, SameSite cookies are sent on cross-origin requests when the "Save Page As..." menu item is selected to save a page, which can result in saving the wrong version of resources based on those cookies. This vulnerability affects Firefox < 63.

Published 2019-02-28 · last modified 2026-06-17.

CVSS v3 metric

CVSS v3 base score 6.5 (Medium). Vector: CVSS:3.0/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:N/A:N.

EPSS exploit prediction

EPSS: 0.013 (69.7th percentile), scored 2026-10-01.

Low probability of exploitation in the next 30 days, but still tracked. 70th percentile — 69.7% of CVEs in the catalogue have a lower EPSS than this one. How to read EPSS.

EPSS over last 30 days · oldest: 0.013 · newest: 0.013 · change: 0.000

Affected products

Mozilla Firefox — versions unspecified
Canonical Ubuntu Linux — versions 14.04, 16.04, 18.04

Weakness classification (CWE)

CWE-346 — Origin Validation Error

References

bugzilla.mozilla.org/show_bug.cgi (Vendor Advisory, Permissions Required, Issue Tracking)
bugzilla.mozilla.org/show_bug.cgi (Vendor Advisory, Permissions Required, Issue Tracking)
www.mozilla.org/security/advisories/mfsa2018-26/ (Vendor Advisory)
www.securityfocus.com/bid/105721 (VDB Entry, Third Party Advisory, vdb-entry)
usn.ubuntu.com/3801-1/ (vendor-advisory, Third Party Advisory)
www.securitytracker.com/id/1041944 (VDB Entry, Third Party Advisory, vdb-entry)

Frequently asked questions

What is CVE-2018-12402?: CVE-2018-12402 is a medium-severity vulnerability in Mozilla Firefox, classified under Origin Validation Error. CVSS score: 6.5/10. Published 2019-02-28.
How severe is CVE-2018-12402?: Medium severity. CVSS v3 base score is 6.5 out of 10.