How severe is CVE-2004-0840?

CVE-2004-0840 has a CVSS 2.0 base score of 10.0, rated critical severity.

Is CVE-2004-0840 being actively exploited?

It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 30% (98th percentile), an estimate of the probability of exploitation in the next 30 days.

What products are affected by CVE-2004-0840?

CVE-2004-0840 primarily affects Microsoft Exchange Server. In total, 4 product configurations (CPEs) are listed as vulnerable; see the affected-products list for the exact versions.

How do I fix CVE-2004-0840?

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-2004-0840 published?

CVE-2004-0840 was published on 2004-11-03 and last updated on 2026-06-16.

CVE-2004-0840

CVE-2004-0840 is a critical-severity vulnerability in Microsoft Exchange Server with a CVSS 2.0 base score of 10.0. Its EPSS exploit-prediction score of 30% places it in the 98th percentile, indicating an elevated likelihood of exploitation. The underlying weakness is classified as CWE-20.

Key facts

Severity: Critical (CVSS 2.0 base score 10.0)
EPSS exploit prediction: 30% (98th percentile)
Actively exploited: Not listed in CISA KEV
Weakness: CWE-20
Affected product: Microsoft Exchange Server
Published: 2004-11-03
Last modified: 2026-06-16

Description

The SMTP (Simple Mail Transfer Protocol) component of Microsoft Windows XP 64-bit Edition, Windows Server 2003, Windows Server 2003 64-bit Edition, and the Exchange Routing Engine component of Exchange Server 2003, allows remote attackers to execute arbitrary code via a malicious DNS response message containing length values that are not properly validated.

Frequently asked questions

What is CVE-2004-0840?: The SMTP (Simple Mail Transfer Protocol) component of Microsoft Windows XP 64-bit Edition, Windows Server 2003, Windows Server 2003 64-bit Edition, and the Exchange Routing Engine component of Exchange Server 2003, allows remote attackers to execute arbitrary code via a malicious DNS response message containing length values that are not properly validated.
How severe is CVE-2004-0840?: CVE-2004-0840 has a CVSS 2.0 base score of 10.0, rated critical severity.
Is CVE-2004-0840 being actively exploited?: It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 30% (98th percentile), an estimate of the probability of exploitation in the next 30 days.
What products are affected by CVE-2004-0840?: CVE-2004-0840 primarily affects Microsoft Exchange Server. In total, 4 product configurations (CPEs) are listed as vulnerable; see the affected-products list for the exact versions.
How do I fix CVE-2004-0840?: 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-2004-0840 published?: CVE-2004-0840 was published on 2004-11-03 and last updated on 2026-06-16.

References

Affected products (4)

cpe:2.3:a:microsoft:exchange_server:2003:-:*:*:*:*:*:*
cpe:2.3:o:microsoft:windows_server_2003:-:*:*:*:*:*:x64:*
cpe:2.3:o:microsoft:windows_server_2003:r2:*:*:*:*:*:*:*
cpe:2.3:o:microsoft:windows_xp:*:*:*:*:*:*:x64:*

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