How severe is CVE-1999-0993?

CVE-1999-0993 has a CVSS 2.0 base score of 7.5, rated high severity.

Is CVE-1999-0993 being actively exploited?

It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 7% (93rd percentile), an estimate of the probability of exploitation in the next 30 days.

What products are affected by CVE-1999-0993?

CVE-1999-0993 primarily affects Microsoft Exchange Server. In total, 2 product configurations (CPEs) are listed as vulnerable; see the affected-products list for the exact versions.

How do I fix CVE-1999-0993?

Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround. Given its high severity, prioritise patching exposed systems.

When was CVE-1999-0993 published?

CVE-1999-0993 was published on 1999-12-13 and last updated on 2026-06-16.

CVE-1999-0993

CVE-1999-0993 is a high-severity vulnerability in Microsoft Exchange Server with a CVSS 2.0 base score of 7.5. 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-665.

Key facts

Severity: High (CVSS 2.0 base score 7.5)
EPSS exploit prediction: 7% (93rd percentile)
Actively exploited: Not listed in CISA KEV
Weakness: CWE-665
Affected product: Microsoft Exchange Server
Published: 1999-12-13
Last modified: 2026-06-16

Description

Modifications to ACLs (Access Control Lists) in Microsoft Exchange 5.5 do not take effect until the directory store cache is refreshed.

Frequently asked questions

What is CVE-1999-0993?: Modifications to ACLs (Access Control Lists) in Microsoft Exchange 5.5 do not take effect until the directory store cache is refreshed.
How severe is CVE-1999-0993?: CVE-1999-0993 has a CVSS 2.0 base score of 7.5, rated high severity.
Is CVE-1999-0993 being actively exploited?: It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 7% (93rd percentile), an estimate of the probability of exploitation in the next 30 days.
What products are affected by CVE-1999-0993?: CVE-1999-0993 primarily affects Microsoft Exchange Server. In total, 2 product configurations (CPEs) are listed as vulnerable; see the affected-products list for the exact versions.
How do I fix CVE-1999-0993?: Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround. Given its high severity, prioritise patching exposed systems.
When was CVE-1999-0993 published?: CVE-1999-0993 was published on 1999-12-13 and last updated on 2026-06-16.

References

https://exchange.xforce.ibmcloud.com/vulnerabilities/CVE-1999-0993

Affected products (2)

cpe:2.3:a:microsoft:exchange_server:5.0:-:*:*:*:*:*:*
cpe:2.3:a:microsoft:exchange_server:5.5:-:*:*:*:*:*:*

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