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CVE-2013-5609: Multiple unspecified vulnerabilities in the browser engine in Mozilla Firefox before 26.0, Firefox ESR 24.x be

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CRITICAL 9.8REMOTEWATCHLISTUPGRADEUPGRADEUPGRADE

CVE-2013-5609 is a critical-severity flaw (CVSS 9.8) affecting firefox, seamonkey, thunderbird. Below: why it ranks where it does, which versions are affected, what to do, and the exact commands.

Multiple unspecified vulnerabilities in the browser engine in Mozilla Firefox before 26.0, Firefox ESR 24.x before 24.2, Thunderbird before 24.2, and SeaMonkey before 2.23 allow remote attackers to cause a denial of service (memory corruption and application crash) or possibly execute arbitrary code via unknown vectors.

Why this priority

  • Critical severity
  • EPSS top 5%: very likely to be exploited
  • Public exploit reference
  • Remotely exploitable, no login, no user action
  • On your watchlist

A fixed release or distro patch exists.

Risk facts

CVSS score9.8 (Critical)
Attack vectorNetwork (remote)
Attack complexityLow
Privileges neededNone
User interactionNone
EPSS exploit chance8.1% (top 5%)
CISA exploited listNo
Published2013-12-11
Last modified2026-06-16
Publisher (CNA): Mozilla Corporation · Vendor: fedoraproject · mozilla · opensuse · suse

Share: LinkedIn · X · Reddit

Last updated 2026-06-16 · Sources: CVE Program, NVD, CISA KEV, EPSS and vendor advisories · How we score

Am I affected?

Timeline

mozilla firefox UPGRADE
Affected: < 26.0 · >= 24.0 and < 24.2
Fixed in: 24.2, 26.0
Safe to downgrade to: a release before 24.0
1. Check installed version
apt-cache policy firefox || rpm -q firefox || firefox --version
2. UPGRADE to 24.2 (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 24.0 (Debian / Ubuntu)
apt-cache madison firefox sudo apt install firefox=<VERSION_BEFORE_24.0> 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_24.0> 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 seamonkey UPGRADE
Affected: < 2.23
Fixed in: 2.23
Safe to downgrade to: no unaffected older release
1. Check installed version
apt-cache policy seamonkey || rpm -q seamonkey || seamonkey --version
2. UPGRADE to 2.23 (Debian / Ubuntu)
sudo apt update && sudo apt install --only-upgrade seamonkey
2. UPGRADE (RHEL / Amazon Linux / Fedora)
sudo dnf upgrade seamonkey
Note
Distros often backport fixes without changing the version number. Confirm with the distro advisory or changelog.
mozilla thunderbird UPGRADE
Affected: < 24.2
Fixed in: 24.2
Safe to downgrade to: no unaffected older release
1. Check installed version
apt-cache policy thunderbird || rpm -q thunderbird || thunderbird --version
2. UPGRADE to 24.2 (Debian / Ubuntu)
sudo apt update && sudo apt install --only-upgrade thunderbird
2. UPGRADE (RHEL / Amazon Linux / Fedora)
sudo dnf upgrade thunderbird
Note
Distros often backport fixes without changing the version number. Confirm with the distro advisory or changelog.
fedoraproject fedora MITIGATE
Affected: 18 · 19 · 20
Fixed in: no fixed release known
Safe to downgrade to: a release before 18
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.
suse suse linux enterprise software development kit DOWNGRADE
Affected: 11.0 sp3
Fixed in: no fixed release known
Safe to downgrade to: a release before 11.0
1. Check installed version
apt-cache policy suse-linux-enterprise-software-development-kit || rpm -q suse-linux-enterprise-software-development-kit || suse-linux-enterprise-software-development-kit --version
2. No fixed release: DOWNGRADE to a release before 11.0 (Debian / Ubuntu)
apt-cache madison suse-linux-enterprise-software-development-kit sudo apt install suse-linux-enterprise-software-development-kit=<VERSION_BEFORE_11.0> sudo apt-mark hold suse-linux-enterprise-software-development-kit
2. No fixed release: DOWNGRADE (RHEL / Amazon Linux / Fedora)
dnf --showduplicates list suse-linux-enterprise-software-development-kit sudo dnf downgrade suse-linux-enterprise-software-development-kit-<VERSION_BEFORE_11.0> sudo dnf versionlock add suse-linux-enterprise-software-development-kit
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.
opensuse opensuse MITIGATE
Affected: 12.2 · 12.3 · 13.1
Fixed in: no fixed release known
Safe to downgrade to: a release before 12.2
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 · rust-ingredients · FIXED · 0.3.3-2.fc46 · FEDORA-2026-0b3d9feffd · source
sudo dnf upgrade --advisory=FEDORA-2026-0b3d9feffd
Fedora ELN · dpkg · FIXED · 1.23.11-2.eln159 · FEDORA-2026-732e4ac21b · source
sudo dnf upgrade --advisory=FEDORA-2026-732e4ac21b
RHEL 5 · firefox · FIXED · firefox-24.2.0-1.el5_10
sudo dnf upgrade --advisory=RHSA-2013:1812 rpm -q firefox
RHEL 5 · thunderbird · FIXED · thunderbird-24.2.0-2.el5_10
sudo dnf upgrade --advisory=RHSA-2013:1823 rpm -q thunderbird
RHEL 6 · firefox · FIXED · firefox-24.2.0-1.el6_5
sudo dnf upgrade --advisory=RHSA-2013:1812 rpm -q firefox
RHEL 6 · thunderbird · FIXED · thunderbird-24.2.0-1.el6_5
sudo dnf upgrade --advisory=RHSA-2013:1823 rpm -q thunderbird
Verify at the official source NVD · CVE Program · 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-2013-5609?

firefox: upgrade to 24.2, 26.0; seamonkey: upgrade to 2.23; thunderbird: upgrade to 24.2. Exact commands for each OS are on this page.

Is CVE-2013-5609 being exploited?

CVE-2013-5609 is not on the CISA Known Exploited Vulnerabilities list at the time of the last update. Check again, as this can change.

What does CVE-2013-5609 affect?

CVE-2013-5609 affects firefox, seamonkey, thunderbird. Severity is critical (CVSS 9.8). Multiple unspecified vulnerabilities in the browser engine in Mozilla Firefox before 26.0, Firefox ESR 24.x before 24.2, Thunderbird before 24.2, and SeaMonkey before 2.23 allow remote attackers to cause a denial of service (memory corrupti

How urgent is CVE-2013-5609?

Priority 73/100. Critical severity; EPSS top 5%: very likely to be exploited; Public exploit reference; Remotely exploitable, no login, no user action; On your watchlist

Software pages

Mozilla Firefox vulnerabilities · Mozilla Thunderbird vulnerabilities

Related CVEs

References

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