Which products and versions are affected by CVE-2004-0380?

Affected: Outlook Express (Microsoft) versions 5.5, 6.0. The full list is in the CVE brief.

Is CVE-2004-0380 being exploited in the wild?

It is exploited in the wild, listed in Industry KEV feed since Feb 13, 2004.

Is CVE-2004-0380 in the CISA KEV catalog?

No, it is not currently listed in the CISA Known Exploited Vulnerabilities catalog.

Is there a public exploit for CVE-2004-0380?

Public exploit code is available.

Is there a fix for CVE-2004-0380?

No fixed version is listed yet; check the vendor advisory for mitigations.

How urgently should CVE-2004-0380 be patched?

Brandefense priority: patch immediately, because it is listed as exploited in the wild.

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Vulnerability Intelligence

CVE-2004-0380

CriticalExploitedPublic exploit

Published May 4, 2004 · Updated Apr 15, 2026

Key Facts

Patch immediately

CVE-2004-0380 is a critical-severity vulnerability (CVSS 10.0 v2) affecting Outlook Express (Microsoft).
It is exploited in the wild, listed in Industry KEV feed since Feb 13, 2004. Public exploit code is available.
EPSS estimates a 63% probability of exploitation in the next 30 days.
No fixed version is listed yet; check the vendor advisory for mitigations.
Brandefense priority: patch immediately, because it is listed as exploited in the wild.

CVSS v2

10.0

AV:N/AC:L/Au:N/C:C/I:C/A:C

EPSS (30-day exploit likelihood)

63%

Higher than 99.2% of all scored CVEs

Exploited in the wild

Yes

1 catalog listing

Public exploit code

Available

Proof-of-concept or weaponized module

Get the full CVE-2004-0380 brief as a PDF

Every affected product and fixed release, exploitation status and a first 24 hours response checklist, emailed within minutes.

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."

Known-Exploited Catalog Listings

Catalog	Added	Remediation due	Ransomware use
Industry KEV feed	Feb 13, 2004	n/a	Not reported

Required action: Apply remediations or mitigations per vendor instructions or discontinue use of the product if remediation or mitigations are unavailable.

Affected Products

2 affected entries in total

Product	Affected versions	Fixed in
Outlook ExpressMicrosoft	5.5, 6.0	n/a

Timeline

Added to Industry KEV feed
Feb 13, 2004
Publicly disclosed
May 4, 2004
Last updated
Apr 15, 2026

References

12 more references in the full CVE brief

FAQ

Common Questions.

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 su…
Affected: Outlook Express (Microsoft) versions 5.5, 6.0. The full list is in the CVE brief.
It is exploited in the wild, listed in Industry KEV feed since Feb 13, 2004.
No, it is not currently listed in the CISA Known Exploited Vulnerabilities catalog.
Public exploit code is available.
No fixed version is listed yet; check the vendor advisory for mitigations.
Brandefense priority: patch immediately, because it is listed as exploited in the wild.

Is CVE-2004-0380 Running On Your Attack Surface?

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