How severe is CVE-2009-5017?

CVE-2009-5017 has a CVSS 2.0 base score of 4.3, rated medium severity.

Is CVE-2009-5017 being actively exploited?

It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 2% (77th percentile), an estimate of the probability of exploitation in the next 30 days.

What products are affected by CVE-2009-5017?

CVE-2009-5017 primarily affects Mozilla Firefox. In total, 2 product configurations (CPEs) are listed as vulnerable; see the affected-products list for the exact versions.

How do I fix CVE-2009-5017?

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

When was CVE-2009-5017 published?

CVE-2009-5017 was published on 2010-11-12 and last updated on 2026-06-16.

CVE-2009-5017

CVE-2009-5017 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% (77th percentile)
Actively exploited: Not listed in CISA KEV
Weakness: CWE-79
Affected product: Mozilla Firefox
Published: 2010-11-12
Last modified: 2026-06-16

Description

Mozilla Firefox before 3.6 Beta 3 does not properly handle overlong UTF-8 encoding, which makes it easier for remote attackers to bypass cross-site scripting (XSS) protection mechanisms via a crafted string, a different vulnerability than CVE-2010-1210.

Frequently asked questions

What is CVE-2009-5017?: Mozilla Firefox before 3.6 Beta 3 does not properly handle overlong UTF-8 encoding, which makes it easier for remote attackers to bypass cross-site scripting (XSS) protection mechanisms via a crafted string, a different vulnerability than CVE-2010-1210.
How severe is CVE-2009-5017?: CVE-2009-5017 has a CVSS 2.0 base score of 4.3, rated medium severity.
Is CVE-2009-5017 being actively exploited?: It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 2% (77th percentile), an estimate of the probability of exploitation in the next 30 days.
What products are affected by CVE-2009-5017?: CVE-2009-5017 primarily affects Mozilla Firefox. In total, 2 product configurations (CPEs) are listed as vulnerable; see the affected-products list for the exact versions.
How do I fix CVE-2009-5017?: Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround.
When was CVE-2009-5017 published?: CVE-2009-5017 was published on 2010-11-12 and last updated on 2026-06-16.

References

Affected products (2)

cpe:2.3:a:mozilla:firefox:*:beta2:*:*:*:*:*:*
cpe:2.3:a:mozilla:firefox:3.6:beta1:*:*:*:*:*:*

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