How severe is CVE-2009-1840?

CVE-2009-1840 has a CVSS 2.0 base score of 9.3, rated critical severity.

Is CVE-2009-1840 being actively exploited?

It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 2% (81st percentile), an estimate of the probability of exploitation in the next 30 days.

What products are affected by CVE-2009-1840?

CVE-2009-1840 primarily affects Mozilla Firefox. In total, 18 product configurations (CPEs) are listed as vulnerable; see the affected-products list for the exact versions.

How do I fix CVE-2009-1840?

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-2009-1840 published?

CVE-2009-1840 was published on 2009-06-12 and last updated on 2026-06-16.

CVE-2009-1840

CVE-2009-1840 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-264.

Key facts

Severity: Critical (CVSS 2.0 base score 9.3)
EPSS exploit prediction: 2% (81st percentile)
Actively exploited: Not listed in CISA KEV
Weakness: CWE-264
Affected product: Mozilla Firefox
Published: 2009-06-12
Last modified: 2026-06-16

Description

Mozilla Firefox before 3.0.11, Thunderbird, and SeaMonkey do not check content policy before loading a script file into a XUL document, which allows remote attackers to bypass intended access restrictions via a crafted HTML document, as demonstrated by a "web bug" in an e-mail message, or web script or an advertisement in a web page.

Frequently asked questions

What is CVE-2009-1840?: Mozilla Firefox before 3.0.11, Thunderbird, and SeaMonkey do not check content policy before loading a script file into a XUL document, which allows remote attackers to bypass intended access restrictions via a crafted HTML document, as demonstrated by a "web bug" in an e-mail message, or web script or an advertisement in a web page.
How severe is CVE-2009-1840?: CVE-2009-1840 has a CVSS 2.0 base score of 9.3, rated critical severity.
Is CVE-2009-1840 being actively exploited?: It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 2% (81st percentile), an estimate of the probability of exploitation in the next 30 days.
What products are affected by CVE-2009-1840?: CVE-2009-1840 primarily affects Mozilla Firefox. In total, 18 product configurations (CPEs) are listed as vulnerable; see the affected-products list for the exact versions.
How do I fix CVE-2009-1840?: 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-2009-1840 published?: CVE-2009-1840 was published on 2009-06-12 and last updated on 2026-06-16.

References

Affected products (18)

cpe:2.3:a:mozilla:firefox:*:*:*:*:*:*:*:*
cpe:2.3:a:mozilla:firefox:3.0:*:*:*:*:*:*:*
cpe:2.3:a:mozilla:firefox:3.0:alpha:*:*:*:*:*:*
cpe:2.3:a:mozilla:firefox:3.0:beta2:*:*:*:*:*:*
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:3.0beta5:*:*:*:*:*:*:*
cpe:2.3:a:mozilla:firefox:3.1:beta1:*:*:*:*:*:*
cpe:2.3:a:mozilla:seamonkey:*:*:*:*:*:*:*:*
cpe:2.3:a:mozilla:thunderbird:*:*:*:*:*:*:*:*

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