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Vulnerabilities

Vulnerability · CVE-2001-0660

Outlook Web Access (OWA) in Microsoft Exchange 5.5, SP4 and earlier, allows remote attackers to identify valid user email addresses by directly accessing a back-end fu…

Published Oct 30, 2001 · catalog updated Jun 16, 2026 · exchange server

Last checked Nov 1, 2026. A connected source was read within the last 7 days.

Check this week

CVE-2001-0660 is not in CISA KEV. FIRST estimates a 21.99% chance of exploitation in the next 30 days. Check whether you run exchange server.

Gaps on this record

  • No vendor fix or required action is stored. Compare the linked advisory before you change production.

Same product and reporting

Severity
Medium5.0
Known exploitation
Not in CISA/VulnCheck KEV
EPSS
21.99%
Remediation
Version ranges on file
Affected products
cpe microsoft/exchange server

Outlook Web Access (OWA) in Microsoft Exchange 5.5, SP4 and earlier, allows remote attackers to identify valid user email addresses by directly accessing a back-end function that processes the global address list (GAL).

Are you affected?

Enter the version you run. The result uses only the ranges stored on this record.

The check returns affected, not affected, or incomplete. It does not guess a version that is missing from the record.

  • cpe microsoft/exchange server<= 5.5

How to fix CVE-2001-0660

  • Upgrade

    CVE-2001-0660 lists a fix boundary at 5.5. Compare the installed build with that boundary before you change production.

  • Version check

    Affected <= 5.5

  • Advisory

    Open the inventory_critical record and follow its fix.

  • Official advisories

What to do

Three questions, each answered from this record only. Confirm the vendor advisory before you patch.

Should you patch?

CVE-2001-0660 is not in CISA KEV. FIRST estimates a 21.99% chance of exploitation in the next 30 days. Check whether you run exchange server.

Which versions are affected?

Compare what you have installed with microsoft/exchange server <= 5.5. Compare the installed version with the linked vendor advisory before you change production.

What should an analyst verify?

No weakness class is stored. EPSS 21.99%. There is no CISA KEV listing. No Exploit-DB or Metasploit reference is linked. Use the source links for the original advisory.

Technology hubs

Microsoft Exchange Server security

Code

The project this record applies to. Exploit listings stay in References.

No public source repository is identified for this product.

Timeline

Detection, updates, and resolution for this record.

  1. Oct 30, 2001 · Monitored products — critical

    Detected

    Outlook Web Access (OWA) in Microsoft Exchange 5.5, SP4 and earlier, allows remote attackers to identify valid user email addresses by directly accessing a back-end function that processes the global address list (GAL).

  2. Jun 16, 2026 · Monitored products — critical

    Updated

    Outlook Web Access (OWA) in Microsoft Exchange 5.5, SP4 and earlier, allows remote attackers to identify valid user email addresses by directly accessing a back-end function that processes the global address list (GAL).

Sources

  • Monitored products — criticalVendor advisoryCVE-2001-0660

    Outlook Web Access (OWA) in Microsoft Exchange 5.5, SP4 and earlier, allows remote attackers to identify valid user email addresses by directly accessing a back-end function that processes the global address list (GAL).

    nvd.nist.gov

References

Freshness

Last verified in this catalog Nov 1, 2026. Significant claims (KEV, EPSS, CVSS, affected ranges) come from the source rows above — open the original publisher for the authoritative advisory.

  • Monitored products — criticalNov 1, 2026