CVE-2009-3376

CVE-2009-3376 is a critical-severity vulnerability in Mozilla Firefox with a CVSS 2.0 base score of 9.3. It is not currently listed as actively exploited by CISA, and its EPSS exploit-prediction score is low. The underlying weakness is classified as CWE-16.

Key facts

• Severity: Critical (CVSS 2.0 base score 9.3)
• EPSS exploit prediction: 3% (87th percentile)
• Actively exploited: Not listed in CISA KEV
• Weakness: CWE-16
• Affected product: Mozilla Firefox
• Published: 2009-10-29
• Last modified: 2026-06-16

Description

Mozilla Firefox before 3.0.15 and 3.5.x before 3.5.4, and SeaMonkey before 2.0, does not properly handle a right-to-left override (aka RLO or U+202E) Unicode character in a download filename, which allows remote attackers to spoof file extensions via a crafted filename, as demonstrated by displaying a non-executable extension for an executable file.

Frequently asked questions

What is CVE-2009-3376?

Mozilla Firefox before 3.0.15 and 3.5.x before 3.5.4, and SeaMonkey before 2.0, does not properly handle a right-to-left override (aka RLO or U+202E) Unicode character in a download filename, which allows remote attackers to spoof file extensions via a crafted filename, as demonstrated by displaying a non-executable extension for an executable file.

How severe is CVE-2009-3376?

CVE-2009-3376 has a CVSS 2.0 base score of 9.3, rated critical severity.

Is CVE-2009-3376 being actively exploited?

It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 3% (87th percentile), an estimate of the probability of exploitation in the next 30 days.

What products are affected by CVE-2009-3376?

CVE-2009-3376 primarily affects Mozilla Firefox. In total, 52 product configurations (CPEs) are listed as vulnerable; see the affected-products list for the exact versions.

How do I fix CVE-2009-3376?

Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround. Given its critical severity, prioritise patching exposed systems.

When was CVE-2009-3376 published?

CVE-2009-3376 was published on 2009-10-29 and last updated on 2026-06-16.

References

• http://lists.opensuse.org/opensuse-security-announce/2010-06/msg00001.html
• http://secunia.com/advisories/38977
• http://sunsolve.sun.com/search/document.do?assetkey=1-26-272909-1
• http://www.mandriva.com/security/advisories?name=MDVSA-2009:294
• http://www.mozilla.org/security/announce/2009/mfsa2009-62.html
• http://www.redhat.com/support/errata/RHSA-2010-0153.html
• http://www.redhat.com/support/errata/RHSA-2010-0154.html
• http://www.ubuntu.com/usn/USN-915-1
• http://www.vupen.com/english/advisories/2009/3334
• http://www.vupen.com/english/advisories/2010/0648
• http://www.vupen.com/english/advisories/2010/0650
• https://bugzilla.mozilla.org/show_bug.cgi?id=511521
• https://oval.cisecurity.org/repository/search/definition/oval%3Aorg.mitre.oval%3Adef%3A11218
• https://oval.cisecurity.org/repository/search/definition/oval%3Aorg.mitre.oval%3Adef%3A6541

Affected products (52)

• cpe:2.3:a:mozilla:firefox:3.0:beta5:*:*:*:*:*:*
• cpe:2.3:a:mozilla:firefox:3.0.1:*:*:*:*:*:*:*
• cpe:2.3:a:mozilla:firefox:3.0.2:*:*:*:*:*:*:*
• cpe:2.3:a:mozilla:firefox:3.0.3:*:*:*:*:*:*:*
• cpe:2.3:a:mozilla:firefox:3.0.4:*:*:*:*:*:*:*
• cpe:2.3:a:mozilla:firefox:3.0.5:*:*:*:*:*:*:*
• cpe:2.3:a:mozilla:firefox:3.0.6:*:*:*:*:*:*:*
• cpe:2.3:a:mozilla:firefox:3.0.7:*:*:*:*:*:*:*
• cpe:2.3:a:mozilla:firefox:3.0.8:*:*:*:*:*:*:*
• cpe:2.3:a:mozilla:firefox:3.0.9:*:*:*:*:*:*:*
• cpe:2.3:a:mozilla:firefox:3.0.10:*:*:*:*:*:*:*
• cpe:2.3:a:mozilla:firefox:3.0.11:*:*:*:*:*:*:*
• cpe:2.3:a:mozilla:firefox:3.0.12:*:*:*:*:*:*:*
• cpe:2.3:a:mozilla:firefox:3.0.13:*:*:*:*:*:*:*
• cpe:2.3:a:mozilla:firefox:3.5.1:*:*:*:*:*:*:*
• cpe:2.3:a:mozilla:firefox:3.5.2:*:*:*:*:*:*:*
• cpe:2.3:a:mozilla:firefox:3.5.3:*:*:*:*:*:*:*
• cpe:2.3:a:mozilla:seamonkey:*:*:*:*:*:*:*:*
• cpe:2.3:a:mozilla:seamonkey:1.0:*:*:*:*:*:*:*
• cpe:2.3:a:mozilla:seamonkey:1.0:alpha:*:*:*:*:*:*
• cpe:2.3:a:mozilla:seamonkey:1.0:beta:*:*:*:*:*:*
• cpe:2.3:a:mozilla:seamonkey:1.0.1:*:*:*:*:*:*:*
• cpe:2.3:a:mozilla:seamonkey:1.0.2:*:*:*:*:*:*:*
• cpe:2.3:a:mozilla:seamonkey:1.0.3:*:*:*:*:*:*:*
• cpe:2.3:a:mozilla:seamonkey:1.0.4:*:*:*:*:*:*:*
• cpe:2.3:a:mozilla:seamonkey:1.0.5:*:*:*:*:*:*:*
• cpe:2.3:a:mozilla:seamonkey:1.0.6:*:*:*:*:*:*:*
• cpe:2.3:a:mozilla:seamonkey:1.0.7:*:*:*:*:*:*:*
• cpe:2.3:a:mozilla:seamonkey:1.0.8:*:*:*:*:*:*:*
• cpe:2.3:a:mozilla:seamonkey:1.0.9:*:*:*:*:*:*:*
• cpe:2.3:a:mozilla:seamonkey:1.1:*:*:*:*:*:*:*
• cpe:2.3:a:mozilla:seamonkey:1.1:alpha:*:*:*:*:*:*
• cpe:2.3:a:mozilla:seamonkey:1.1:beta:*:*:*:*:*:*
• cpe:2.3:a:mozilla:seamonkey:1.1.1:*:*:*:*:*:*:*
• cpe:2.3:a:mozilla:seamonkey:1.1.2:*:*:*:*:*:*:*
• cpe:2.3:a:mozilla:seamonkey:1.1.3:*:*:*:*:*:*:*
• cpe:2.3:a:mozilla:seamonkey:1.1.4:*:*:*:*:*:*:*
• cpe:2.3:a:mozilla:seamonkey:1.1.5:*:*:*:*:*:*:*
• cpe:2.3:a:mozilla:seamonkey:1.1.6:*:*:*:*:*:*:*
• cpe:2.3:a:mozilla:seamonkey:1.1.7:*:*:*:*:*:*:*

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