CVE-2004-0380

CVE-2004-0380 is a critical-severity vulnerability in Microsoft Outlook Express with a CVSS 2.0 base score of 10.0. Its EPSS exploit-prediction score of 63% places it in the 99th percentile, indicating an elevated likelihood of exploitation.

Key facts

Description

The MHTML protocol handler in Microsoft Outlook Express 5.5 SP2 through Outlook Express 6 SP1 allows remote attackers to bypass domain restrictions and execute arbitrary code, as demonstrated on Internet Explorer using script in a compiled help (CHM) file that references the InfoTech Storage (ITS) protocol handlers such as (1) ms-its, (2) ms-itss, (3) its, or (4) mk:@MSITStore, aka the "MHTML URL Processing Vulnerability."

Frequently asked questions

What is CVE-2004-0380?
The MHTML protocol handler in Microsoft Outlook Express 5.5 SP2 through Outlook Express 6 SP1 allows remote attackers to bypass domain restrictions and execute arbitrary code, as demonstrated on Internet Explorer using script in a compiled help (CHM) file that references the InfoTech Storage (ITS) protocol handlers such as (1) ms-its, (2) ms-itss, (3) its, or (4) mk:@MSITStore, aka the "MHTML URL Processing Vulnerability."
How severe is CVE-2004-0380?
CVE-2004-0380 has a CVSS 2.0 base score of 10.0, rated critical severity.
Is CVE-2004-0380 being actively exploited?
It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 63% (99th percentile), an estimate of the probability of exploitation in the next 30 days.
What products are affected by CVE-2004-0380?
CVE-2004-0380 primarily affects Microsoft Outlook Express. In total, 2 product configurations (CPEs) are listed as vulnerable; see the affected-products list for the exact versions.
How do I fix CVE-2004-0380?
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-2004-0380 published?
CVE-2004-0380 was published on 2004-05-04 and last updated on 2026-06-16.

References

Affected products (2)

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