How severe is CVE-1999-1164?

CVE-1999-1164 has a CVSS 2.0 base score of 5.0, rated medium severity.

Is CVE-1999-1164 being actively exploited?

It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 13% (96th percentile), an estimate of the probability of exploitation in the next 30 days.

What products are affected by CVE-1999-1164?

CVE-1999-1164 primarily affects Microsoft Outlook. In total, 4 product configurations (CPEs) are listed as vulnerable; see the affected-products list for the exact versions.

How do I fix CVE-1999-1164?

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

When was CVE-1999-1164 published?

CVE-1999-1164 was published on 1999-06-25 and last updated on 2026-06-16.

CVE-1999-1164

CVE-1999-1164 is a medium-severity vulnerability in Microsoft Outlook with a CVSS 2.0 base score of 5.0. Its EPSS exploit-prediction score of 13% places it in the 96th percentile, indicating an elevated likelihood of exploitation.

Key facts

Severity: Medium (CVSS 2.0 base score 5.0)
EPSS exploit prediction: 13% (96th percentile)
Actively exploited: Not listed in CISA KEV
Affected product: Microsoft Outlook
Published: 1999-06-25
Last modified: 2026-06-16

Description

Microsoft Outlook client allows remote attackers to cause a denial of service by sending multiple email messages with the same X-UIDL headers, which causes Outlook to hang.

Frequently asked questions

What is CVE-1999-1164?: Microsoft Outlook client allows remote attackers to cause a denial of service by sending multiple email messages with the same X-UIDL headers, which causes Outlook to hang.
How severe is CVE-1999-1164?: CVE-1999-1164 has a CVSS 2.0 base score of 5.0, rated medium severity.
Is CVE-1999-1164 being actively exploited?: It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 13% (96th percentile), an estimate of the probability of exploitation in the next 30 days.
What products are affected by CVE-1999-1164?: CVE-1999-1164 primarily affects Microsoft Outlook. In total, 4 product configurations (CPEs) are listed as vulnerable; see the affected-products list for the exact versions.
How do I fix CVE-1999-1164?: Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround.
When was CVE-1999-1164 published?: CVE-1999-1164 was published on 1999-06-25 and last updated on 2026-06-16.

References

http://marc.info/?l=bugtraq&m=93041631215856&w=2

Affected products (4)

cpe:2.3:a:microsoft:outlook:97:*:*:*:*:*:*:*
cpe:2.3:a:microsoft:outlook:98:*:*:*:*:*:*:*
cpe:2.3:a:microsoft:outlook:2000:*:*:*:*:*:*:*
cpe:2.3:a:microsoft:outlook_express:*:*:*:*:*:*:*:*

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