Exploited. On CISA's list since 2022-05-25.
Mozilla Firefox Security Feature Bypass Vulnerability
CVE-2015-4495 · Mozilla Firefox · Published 2015-08-08
How bad would it be?
8.8 out of 10
CVSS rates it high.
How likely is it to be used?
69%
Estimated chance of exploitation in the next 30 days, among the top 1% of all scored flaws (EPSS, 2026-10-29).
Is it already being used?
Yes
CISA has seen it exploited in real attacks. For US government agencies the fix is deadline passed 1598 days ago (2022-06-15).
What CISA says to do
Apply updates per vendor instructions.
Moxilla Firefox allows remote attackers to bypass the Same Origin Policy to read arbitrary files or gain privileges.
What the flaw is
The PDF reader in Mozilla Firefox before 39.0.3, Firefox ESR 38.x before 38.1.1, and Firefox OS before 2.2 allows remote attackers to bypass the Same Origin Policy, and read arbitrary files or gain privileges, via vectors involving crafted JavaScript code and a native setter, as exploited in the wild in August 2015.
From the NVD.
Fixes and advisories
Learn this
Explore this week’s weaknesses and all learning topics
Understand the kind of weakness behind this flaw. These resources teach the weakness, rather than reproduce this specific CVE. Follow the vendor's advice above to fix the affected product.
CWE-200 · CISA KEV. We have not selected a close learning match for this label.
CWE-346 · NVD record: 134c704f-9b21-4f2e-91b3-4a467353bcc0. We have not selected a close learning match for this label.
CWE is a catalogue of weakness types. Labels come from the sources shown and can differ or change. Resource matches reviewed 16 October 2026.
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Exploited flaws from CISA's KEV catalogue. Chance of exploitation from EPSS by FIRST. Descriptions and scores from the NVD. This product uses the NVD API but is not endorsed or certified by the NVD.