PatchTheCVECVE-2013-6671: The nsGfxScrollFrameInner::IsLTR function in Mozilla Firefox before 26.0, Firefox ESR 24.x before 24.2, Thunde
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This week
CRITICAL 9.8REMOTEWATCHLISTUPGRADEUPGRADEUPGRADE
CVE-2013-6671 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.
The nsGfxScrollFrameInner::IsLTR function in Mozilla Firefox before 26.0, Firefox ESR 24.x before 24.2, Thunderbird before 24.2, and SeaMonkey before 2.23 allows remote attackers to execute arbitrary code via crafted use of JavaScript code for ordered list elements.
Why this priority
- Critical severity
- EPSS top 4%: 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 score | 9.8 (Critical) |
| Attack vector | Network (remote) |
| Attack complexity | Low |
| Privileges needed | None |
| User interaction | None |
| EPSS exploit chance | 11.1% (top 4%) |
| CISA exploited list | No |
| Weakness | CWE-94 |
| Published | 2013-12-11 |
| Last modified | 2026-06-17 |
Last updated 2026-06-17 · Sources: CVE Program, NVD, CISA KEV, EPSS and vendor advisories · How we score
Am I affected?
Timeline
- Published CVE record published
- Updated Record last modified
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.
canonical ubuntu linux MITIGATE
Affected: 12.04 · 12.10 · 13.04 · 13.10
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
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: 6.5
Fixed in: no fixed release known
Safe to downgrade to: a release before 6.5
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.
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-2013-6671?
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-2013-6671 being exploited?
CVE-2013-6671 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-2013-6671 affect?
CVE-2013-6671 affects firefox, seamonkey, thunderbird. Severity is critical (CVSS 9.8). The nsGfxScrollFrameInner::IsLTR function in Mozilla Firefox before 26.0, Firefox ESR 24.x before 24.2, Thunderbird before 24.2, and SeaMonkey before 2.23 allows remote attackers to execute arbitrary code via crafted use of JavaScript code
How urgent is CVE-2013-6671?
Priority 73/100. Critical severity; EPSS top 4%: very likely to be exploited; Public exploit reference; Remotely exploitable, no login, no user action; On your watchlist
Software pages
Ubuntu vulnerabilities · Mozilla Firefox vulnerabilities · Mozilla Thunderbird vulnerabilities
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