Free and open · new CVEs checked every 20 minutesStatusRSSOpen dataContact

CVE-2015-4495: Mozilla Firefox Security Feature Bypass Vulnerability

91
Patch now
HIGH 8.8EXPLOITEDWATCHLISTUPGRADEUPGRADEMITIGATE

CVE-2015-4495 is a high-severity flaw (CVSS 8.8) affecting firefox, firefox os, solaris, reported as exploited in the wild. Below: why it ranks where it does, which versions are affected, what to do, and the exact commands.

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.

Why this priority

  • High severity
  • EPSS top 1%: very likely to be exploited
  • Exploited in the wild (CISA KEV)
  • Public exploit reference
  • On your watchlist

A fixed release or distro patch exists.

Risk facts

CVSS score8.8 (High)
Attack vectorNetwork (remote)
Attack complexityLow
Privileges neededNone
User interactionRequired
EPSS exploit chance68.6% (top 1%)
CISA exploited listYes, fix due 2022-06-15
WeaknessCWE-346
Published2015-08-08
Last modified2026-06-17
Publisher (CNA): Mozilla Corporation · Vendor: canonical · mozilla · oracle · redhat

Share: LinkedIn · X · Reddit

Last updated 2026-06-17 · Sources: CVE Program, NVD, CISA KEV, EPSS and vendor advisories · How we score

Am I affected?

Timeline

mozilla firefox UPGRADE
Affected: < 39.0.3 · >= 38.0 and < 38.1.1
Fixed in: 38.1.1, 39.0.3
Safe to downgrade to: a release before 38.0
1. Check installed version
apt-cache policy firefox || rpm -q firefox || firefox --version
2. UPGRADE to 38.1.1 (Debian / Ubuntu)
sudo apt update && sudo apt install --only-upgrade firefox
2. UPGRADE (RHEL / Amazon Linux / Fedora)
sudo dnf upgrade firefox
Note
Distros often backport fixes without changing the version number. Confirm with the distro advisory or changelog.
3. If no update is available yet, DOWNGRADE to a release before 38.0 (Debian / Ubuntu)
apt-cache madison firefox sudo apt install firefox=<VERSION_BEFORE_38.0> sudo apt-mark hold firefox
3. If no update is available yet, DOWNGRADE (RHEL / Amazon Linux / Fedora)
dnf --showduplicates list firefox sudo dnf downgrade firefox-<VERSION_BEFORE_38.0> sudo dnf versionlock add firefox
Downgrade risk
Downgrading can break dependent software and may reopen older bugs. Read the distro advisory first and test on a non-production host.
After downgrade
Restart the service, and keep the package held until a fixed release ships.
mozilla firefox os UPGRADE
Affected: < 2.2
Fixed in: 2.2
Safe to downgrade to: no unaffected older release
Check your OS release
cat /etc/os-release; uname -r
Debian / Ubuntu
sudo apt update && sudo apt full-upgrade
RHEL / Amazon Linux / Fedora
sudo dnf upgrade --refresh
Windows
Install the latest cumulative update from Windows Update
If no patch exists yet
OS downgrades are not safe. Apply the vendor mitigation from the advisory and restrict exposure.
oracle solaris MITIGATE
Affected: 11.3
Fixed in: no fixed release known
Safe to downgrade to: a release before 11.3
Check your OS release
cat /etc/os-release; uname -r
Debian / Ubuntu
sudo apt update && sudo apt full-upgrade
RHEL / Amazon Linux / Fedora
sudo dnf upgrade --refresh
Windows
Install the latest cumulative update from Windows Update
If no patch exists yet
OS downgrades are not safe. Apply the vendor mitigation from the advisory and restrict exposure.
canonical ubuntu linux MITIGATE
Affected: 12.04 · 14.04 · 15.04
Fixed in: no fixed release known
Safe to downgrade to: a release before 12.04
Check your OS release
cat /etc/os-release; uname -r
Debian / Ubuntu
sudo apt update && sudo apt full-upgrade
RHEL / Amazon Linux / Fedora
sudo dnf upgrade --refresh
Windows
Install the latest cumulative update from Windows Update
If no patch exists yet
OS downgrades are not safe. Apply the vendor mitigation from the advisory and restrict exposure.
redhat enterprise linux desktop MITIGATE
Affected: 5.0 · 6.0 · 7.0
Fixed in: no fixed release known
Safe to downgrade to: a release before 5.0
Check your OS release
cat /etc/os-release; uname -r
Debian / Ubuntu
sudo apt update && sudo apt full-upgrade
RHEL / Amazon Linux / Fedora
sudo dnf upgrade --refresh
Windows
Install the latest cumulative update from Windows Update
If no patch exists yet
OS downgrades are not safe. Apply the vendor mitigation from the advisory and restrict exposure.
redhat enterprise linux eus MITIGATE
Affected: 6.7 · 7.1 · 7.2 · 7.3 · 7.4 · 7.5 · 7.6 · 7.7
Fixed in: no fixed release known
Safe to downgrade to: a release before 6.7
Check your OS release
cat /etc/os-release; uname -r
Debian / Ubuntu
sudo apt update && sudo apt full-upgrade
RHEL / Amazon Linux / Fedora
sudo dnf upgrade --refresh
Windows
Install the latest cumulative update from Windows Update
If no patch exists yet
OS downgrades are not safe. Apply the vendor mitigation from the advisory and restrict exposure.

Exact fixes by distribution

A distro patch exists: prefer upgrading over downgrading.
Fedora 46 · perl-Net-IDN-Encode · FIXED · 2.600-1.fc46 · FEDORA-2026-84eff0ea64 · source
sudo dnf upgrade --advisory=FEDORA-2026-84eff0ea64
Fedora ELN · libXISF · FIXED · 0.2.15-2.eln159 · FEDORA-2026-b9e2d1bda0 · source
sudo dnf upgrade --advisory=FEDORA-2026-b9e2d1bda0
Debian 12 · pdf.js · FIXED · 1.1.366+dfsg-1
sudo apt update && sudo apt install --only-upgrade pdf.js dpkg --compare-versions "$(dpkg-query -W -f='${Version}' pdf.js)" ge "1.1.366+dfsg-1" && echo PATCHED || echo STILL-VULNERABLE
Debian 13 · pdf.js · FIXED · 1.1.366+dfsg-1
sudo apt update && sudo apt install --only-upgrade pdf.js dpkg --compare-versions "$(dpkg-query -W -f='${Version}' pdf.js)" ge "1.1.366+dfsg-1" && echo PATCHED || echo STILL-VULNERABLE
RHEL 5 · firefox · FIXED · firefox-38.1.1-1.el5_11
sudo dnf upgrade --advisory=RHSA-2015:1581 rpm -q firefox
RHEL 6 · firefox · FIXED · firefox-38.1.1-1.el6_7
sudo dnf upgrade --advisory=RHSA-2015:1581 rpm -q firefox
RHEL 7 · firefox · FIXED · firefox-38.1.1-1.ael7b_1
sudo dnf upgrade --advisory=RHSA-2015:1581 rpm -q firefox
RHEL 5 · thunderbird · NOT AFFECTED
RHEL 6 · thunderbird · NOT AFFECTED

Public exploits and detection

Public code exists for this CVE. Treat unpatched systems as at risk, and only run PoCs in a lab.

Verify at the official source NVD · CVE Program · CISA KEV catalog · Report a problem with this page
Scores and fixes here are computed automatically from those and other public sources. Confirm with the vendor advisory before changing production systems.

Quick answers

How do I fix CVE-2015-4495?

firefox: upgrade to 38.1.1, 39.0.3; firefox os: upgrade to 2.2; solaris: mitigate or apply the listed mitigation. Exact commands for each OS are on this page.

Is CVE-2015-4495 being exploited?

Yes. CVE-2015-4495 is on the CISA Known Exploited Vulnerabilities list, so treat it as patch-now.

What does CVE-2015-4495 affect?

CVE-2015-4495 affects firefox, firefox os, solaris. Severity is high (CVSS 8.8). 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

How urgent is CVE-2015-4495?

Priority 91/100. High severity; EPSS top 1%: very likely to be exploited; Exploited in the wild (CISA KEV); Public exploit reference; On your watchlist

Software pages

Ubuntu vulnerabilities · Mozilla Firefox vulnerabilities

Related CVEs

References

← Back to latest CVEs

Get the weekly exploited-CVE digest by emailThe CVEs being attacked this week and how to fix them. No spam, unsubscribe any time.