How severe is CVE-2009-4129?

CVE-2009-4129 has a CVSS 2.0 base score of 5.8, rated medium severity.

Is CVE-2009-4129 being actively exploited?

It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 1% (51st percentile), an estimate of the probability of exploitation in the next 30 days.

What products are affected by CVE-2009-4129?

CVE-2009-4129 affects Mozilla Firefox. See the affected-products list for the exact vulnerable versions.

How do I fix CVE-2009-4129?

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

When was CVE-2009-4129 published?

CVE-2009-4129 was published on 2009-12-14 and last updated on 2026-06-16.

CVE-2009-4129

CVE-2009-4129 is a medium-severity vulnerability in Mozilla Firefox with a CVSS 2.0 base score of 5.8. 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-362.

Key facts

Severity: Medium (CVSS 2.0 base score 5.8)
EPSS exploit prediction: 1% (51st percentile)
Actively exploited: Not listed in CISA KEV
Weakness: CWE-362
Affected product: Mozilla Firefox
Published: 2009-12-14
Last modified: 2026-06-16

Description

Race condition in Mozilla Firefox allows remote attackers to produce a JavaScript message with a spoofed domain association by writing the message in between the document request and document load for a web page in a different domain.

Frequently asked questions

What is CVE-2009-4129?: Race condition in Mozilla Firefox allows remote attackers to produce a JavaScript message with a spoofed domain association by writing the message in between the document request and document load for a web page in a different domain.
How severe is CVE-2009-4129?: CVE-2009-4129 has a CVSS 2.0 base score of 5.8, rated medium severity.
Is CVE-2009-4129 being actively exploited?: It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 1% (51st percentile), an estimate of the probability of exploitation in the next 30 days.
What products are affected by CVE-2009-4129?: CVE-2009-4129 affects Mozilla Firefox. See the affected-products list for the exact vulnerable versions.
How do I fix CVE-2009-4129?: Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround.
When was CVE-2009-4129 published?: CVE-2009-4129 was published on 2009-12-14 and last updated on 2026-06-16.

References

Affected products (1)

cpe:2.3:a:mozilla:firefox:*:*:*:*:*:*:*:*

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