How severe is CVE-2008-4066?

CVE-2008-4066 has a CVSS 2.0 base score of 4.3, rated medium severity.

Is CVE-2008-4066 being actively exploited?

It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 2% (75th percentile), an estimate of the probability of exploitation in the next 30 days.

What products are affected by CVE-2008-4066?

CVE-2008-4066 primarily affects Mozilla Firefox. In total, 3 product configurations (CPEs) are listed as vulnerable; see the affected-products list for the exact versions.

How do I fix CVE-2008-4066?

Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround.

When was CVE-2008-4066 published?

CVE-2008-4066 was published on 2008-09-24 and last updated on 2026-06-16.

CVE-2008-4066

CVE-2008-4066 is a medium-severity vulnerability in Mozilla Firefox with a CVSS 2.0 base score of 4.3. 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-79.

Key facts

Severity: Medium (CVSS 2.0 base score 4.3)
EPSS exploit prediction: 2% (75th percentile)
Actively exploited: Not listed in CISA KEV
Weakness: CWE-79
Affected product: Mozilla Firefox
Published: 2008-09-24
Last modified: 2026-06-16

Description

Mozilla Firefox 2.0.0.14, and other versions before 2.0.0.17, allows remote attackers to bypass cross-site scripting (XSS) protection mechanisms and conduct XSS attacks via HTML-escaped low surrogate characters that are ignored by the HTML parser, as demonstrated by a "jav&#56325ascript" sequence, aka "HTML escaped low surrogates bug."

Frequently asked questions

What is CVE-2008-4066?: Mozilla Firefox 2.0.0.14, and other versions before 2.0.0.17, allows remote attackers to bypass cross-site scripting (XSS) protection mechanisms and conduct XSS attacks via HTML-escaped low surrogate characters that are ignored by the HTML parser, as demonstrated by a "jav&#56325ascript" sequence, aka "HTML escaped low surrogates bug."
How severe is CVE-2008-4066?: CVE-2008-4066 has a CVSS 2.0 base score of 4.3, rated medium severity.
Is CVE-2008-4066 being actively exploited?: It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 2% (75th percentile), an estimate of the probability of exploitation in the next 30 days.
What products are affected by CVE-2008-4066?: CVE-2008-4066 primarily affects Mozilla Firefox. In total, 3 product configurations (CPEs) are listed as vulnerable; see the affected-products list for the exact versions.
How do I fix CVE-2008-4066?: Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround.
When was CVE-2008-4066 published?: CVE-2008-4066 was published on 2008-09-24 and last updated on 2026-06-16.

References

Affected products (3)

cpe:2.3:a:mozilla:firefox:2.0.0.14:*:*:*:*:*:*:*
cpe:2.3:a:mozilla:firefox:2.0.0.15:*:*:*:*:*:*:*
cpe:2.3:a:mozilla:firefox:2.0.0.16:*:*:*:*:*:*:*

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