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Vulnerability record · CVE-2015-4495 · published 8 August 2015

CVE-2015-4495: Firefox PDF reader same-origin bypass allows file read and privilege gain

Mozilla · Firefox

The PDF reader in Mozilla Firefox (before 39.0.3), Firefox ESR 38.x (before 38.1.1), and Firefox OS (before 2.2) fails to properly validate origin, letting crafted JavaScript combined with a native setter bypass the Same Origin Policy. This matters because it enables reading arbitrary local files and privilege escalation, and Mozilla confirmed it was exploited in the wild in August 2015.

8.8 CVSS 3.1 High CISA KEV since 25 May 2022 EPSS 69% · top 0.7% CWE-346 · Origin validation error
8.8CVSS 3.1 base score, v2 4.3
69%EPSS exploitation probability, 30 days
YesIn CISA KEV, fix deadline passed
15Affected product versions listed by NVD
35References, 2 tagged exploit
17 Jun 2026Last modified by NVD

Description

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.

CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H

Automated analysis

Generated by VULONE's analysis model from the NVD record, CISA KEV and EPSS data on 17 September 2026. Confidence: high.

critical priorityConfirmed in-the-wild exploitation, CISA KEV listing, and a high EPSS score with high confidentiality, integrity, and availability impact make this an urgent patch target.

What it 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) fails to properly validate origin, letting crafted JavaScript combined with a native setter bypass the Same Origin Policy. This matters because it enables reading arbitrary local files and privilege escalation, and Mozilla confirmed it was exploited in the wild in August 2015.

Impact

An attacker can read arbitrary files on the victim's system and gain privileges, breaking the browser's core isolation boundary. This can expose local secrets and enable further compromise of the host.

Attack surface

Reached remotely over the network through crafted JavaScript in a PDF opened in the affected Firefox PDF reader; the CVSS vector (AV:N/PR:N/UI:R) indicates no authentication is needed but user interaction is required to open the malicious content.

Exploitation

Exploitation is confirmed: the description states it was exploited in the wild in August 2015, it is listed in CISA KEV (added 2022-05-25), and an Exploit-DB entry exists; EPSS is 0.71434 (99.4th percentile).

What to do

  • Update Firefox to 39.0.3 or later, Firefox ESR to 38.1.1 or later, and Firefox OS to 2.2 or later per Mozilla MFSA 2015-78.
  • Apply vendor patches for bundled or derived packages (Red Hat, Ubuntu, SUSE/openSUSE, Oracle Solaris) listed in the advisories.
  • Disable or restrict the built-in PDF viewer where feasible until patching is complete.
  • Block or sandbox untrusted PDF and JavaScript content delivered through the browser.
  • Track CISA KEV remediation due date (2022-06-15) for any remaining unpatched systems.

Detection

  • Monitor for Firefox processes reading unexpected local files outside normal profile paths.
  • Hunt for PDF files containing JavaScript that invoke native setters or attempt cross-origin access.
  • Review proxy and email logs for delivery of PDFs with embedded JavaScript to Firefox users.
  • Alert on Firefox versions below 39.0.3 / ESR 38.1.1 present in the environment.

This assessment is produced automatically and is not human-reviewed. Verify against the vendor advisory before acting on it.

Exploitation in the wild

CISA added CVE-2015-4495 to the Known Exploited Vulnerabilities catalog on 25 May 2022 as "Mozilla Firefox Security Feature Bypass Vulnerability". Required action: Apply updates per vendor instructions. Federal deadline 15 June 2022.

Affected products

15 vulnerable configurations from NVD's CPE data, grouped by vendor and product.

References

LinkTags
http://lists.opensuse.org/opensuse-security-announce/2015-08/msg00009.html Mailing ListThird Party Advisory
http://lists.opensuse.org/opensuse-security-announce/2015-08/msg00010.html Mailing ListThird Party Advisory
http://lists.opensuse.org/opensuse-security-announce/2015-08/msg00014.html Mailing ListThird Party Advisory
http://lists.opensuse.org/opensuse-security-announce/2015-08/msg00015.html Mailing ListThird Party Advisory
http://lists.opensuse.org/opensuse-security-announce/2015-08/msg00021.html Mailing ListThird Party Advisory
http://lists.opensuse.org/opensuse-security-announce/2015-09/msg00016.html Mailing ListThird Party Advisory
http://rhn.redhat.com/errata/RHSA-2015-1581.html Third Party Advisory
http://www.mozilla.org/security/announce/2015/mfsa2015-78.html Vendor Advisory
http://www.oracle.com/technetwork/topics/security/bulletinapr2016-2952098.html PatchThird Party Advisory
http://www.securityfocus.com/bid/76249 Broken LinkThird Party AdvisoryVDB Entry
http://www.securitytracker.com/id/1033216 Broken LinkThird Party AdvisoryVDB Entry
http://www.ubuntu.com/usn/USN-2707-1 Third Party Advisory
https://blog.mozilla.org/security/2015/08/06/firefox-exploit-found-in-the-wild/ Issue TrackingVendor Advisory
https://bugzilla.mozilla.org/show_bug.cgi?id=1178058 Issue Tracking
https://bugzilla.mozilla.org/show_bug.cgi?id=1179262 Issue Tracking
https://security.gentoo.org/glsa/201512-10 Third Party Advisory
https://www.exploit-db.com/exploits/37772/ ExploitThird Party AdvisoryVDB Entry
http://lists.opensuse.org/opensuse-security-announce/2015-08/msg00009.html Mailing ListThird Party Advisory
http://lists.opensuse.org/opensuse-security-announce/2015-08/msg00010.html Mailing ListThird Party Advisory
http://lists.opensuse.org/opensuse-security-announce/2015-08/msg00014.html Mailing ListThird Party Advisory
http://lists.opensuse.org/opensuse-security-announce/2015-08/msg00015.html Mailing ListThird Party Advisory
http://lists.opensuse.org/opensuse-security-announce/2015-08/msg00021.html Mailing ListThird Party Advisory
http://lists.opensuse.org/opensuse-security-announce/2015-09/msg00016.html Mailing ListThird Party Advisory
http://rhn.redhat.com/errata/RHSA-2015-1581.html Third Party Advisory
http://www.mozilla.org/security/announce/2015/mfsa2015-78.html Vendor Advisory
http://www.oracle.com/technetwork/topics/security/bulletinapr2016-2952098.html PatchThird Party Advisory
http://www.securityfocus.com/bid/76249 Broken LinkThird Party AdvisoryVDB Entry
http://www.securitytracker.com/id/1033216 Broken LinkThird Party AdvisoryVDB Entry
http://www.ubuntu.com/usn/USN-2707-1 Third Party Advisory
https://blog.mozilla.org/security/2015/08/06/firefox-exploit-found-in-the-wild/ Issue TrackingVendor Advisory
https://bugzilla.mozilla.org/show_bug.cgi?id=1178058 Issue Tracking
https://bugzilla.mozilla.org/show_bug.cgi?id=1179262 Issue Tracking
https://security.gentoo.org/glsa/201512-10 Third Party Advisory
https://www.exploit-db.com/exploits/37772/ ExploitThird Party AdvisoryVDB Entry
https://www.cisa.gov/known-exploited-vulnerabilities-catalog?field_cve=CVE-2015-4495 US Government Resource

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Source: NIST National Vulnerability Database (record CVE-2015-4495), CISA KEV, FIRST EPSS (scores of 2026-09-26). This page is refreshed as NVD updates the record.