How severe is CVE-2001-0509?

CVE-2001-0509 has a CVSS 2.0 base score of 5.0, rated medium severity.

Is CVE-2001-0509 being actively exploited?

It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 17% (97th percentile), an estimate of the probability of exploitation in the next 30 days.

What products are affected by CVE-2001-0509?

CVE-2001-0509 primarily affects Microsoft Exchange Server. In total, 9 product configurations (CPEs) are listed as vulnerable; see the affected-products list for the exact versions.

How do I fix CVE-2001-0509?

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

When was CVE-2001-0509 published?

CVE-2001-0509 was published on 2001-09-20 and last updated on 2026-06-16.

CVE-2001-0509

CVE-2001-0509 is a medium-severity vulnerability in Microsoft Exchange Server with a CVSS 2.0 base score of 5.0. Its EPSS exploit-prediction score of 17% places it in the 97th percentile, indicating an elevated likelihood of exploitation. The underlying weakness is classified as CWE-20.

Key facts

Severity: Medium (CVSS 2.0 base score 5.0)
EPSS exploit prediction: 17% (97th percentile)
Actively exploited: Not listed in CISA KEV
Weakness: CWE-20
Affected product: Microsoft Exchange Server
Published: 2001-09-20
Last modified: 2026-06-16

Description

Vulnerabilities in RPC servers in (1) Microsoft Exchange Server 2000 and earlier, (2) Microsoft SQL Server 2000 and earlier, (3) Windows NT 4.0, and (4) Windows 2000 allow remote attackers to cause a denial of service via malformed inputs.

Frequently asked questions

What is CVE-2001-0509?: Vulnerabilities in RPC servers in (1) Microsoft Exchange Server 2000 and earlier, (2) Microsoft SQL Server 2000 and earlier, (3) Windows NT 4.0, and (4) Windows 2000 allow remote attackers to cause a denial of service via malformed inputs.
How severe is CVE-2001-0509?: CVE-2001-0509 has a CVSS 2.0 base score of 5.0, rated medium severity.
Is CVE-2001-0509 being actively exploited?: It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 17% (97th percentile), an estimate of the probability of exploitation in the next 30 days.
What products are affected by CVE-2001-0509?: CVE-2001-0509 primarily affects Microsoft Exchange Server. In total, 9 product configurations (CPEs) are listed as vulnerable; see the affected-products list for the exact versions.
How do I fix CVE-2001-0509?: Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround.
When was CVE-2001-0509 published?: CVE-2001-0509 was published on 2001-09-20 and last updated on 2026-06-16.

References

Affected products (9)

cpe:2.3:a:microsoft:exchange_server:5.0:-:*:*:*:*:*:*
cpe:2.3:a:microsoft:exchange_server:5.5:-:*:*:*:*:*:*
cpe:2.3:a:microsoft:exchange_server:2000:-:*:*:*:*:*:*
cpe:2.3:a:microsoft:sql_server:7.0:-:*:*:*:*:*:*
cpe:2.3:a:microsoft:sql_server:2000:-:*:*:*:*:*:*
cpe:2.3:a:microsoft:windows_nt:4.0:*:*:*:*:*:*:*
cpe:2.3:o:microsoft:windows_2000:-:-:*:*:*:*:*:*
cpe:2.3:o:microsoft:windows_2000:*:*:*:*:*:*:*:*
cpe:2.3:o:microsoft:windows_nt:4.0:*:*:*:*:*:*:*

More vulnerabilities in Microsoft Exchange Server

CVE-2007-0213 — Critical (CVSS 10.0): Microsoft Exchange Server 2000 SP3, 2003 SP1 and SP2, and 2007 does not properly decode certain MIME encoded e-mails,…
CVE-2004-0840 — Critical (CVSS 10.0): The SMTP (Simple Mail Transfer Protocol) component of Microsoft Windows XP 64-bit Edition, Windows Server 2003, Windows…
CVE-2004-0574 — Critical (CVSS 10.0): The Network News Transfer Protocol (NNTP) component of Microsoft Windows NT Server 4.0, Windows 2000 Server, Windows…
CVE-1999-0385 — Critical (CVSS 10.0): The LDAP bind function in Exchange 5.5 has a buffer overflow that allows a remote attacker to conduct a denial of…
CVE-2024-21410 — Critical (CVSS 9.8): Microsoft Exchange Server Elevation of Privilege Vulnerability
CVE-2023-21709 — Critical (CVSS 9.8): Microsoft Exchange Server Elevation of Privilege Vulnerability

All CVEs affecting Microsoft Exchange Server →

Other CWE-20 (Improper Input Validation) vulnerabilities

CVE-2026-48316 — Critical (CVSS 10.0): ColdFusion versions 2025.9, 2023.20 and earlier are affected by an Improper Input Validation vulnerability that could…
CVE-2026-48281 — Critical (CVSS 10.0): ColdFusion versions 2025.9, 2023.20 and earlier are affected by an Improper Input Validation vulnerability that could…
CVE-2026-48277 — Critical (CVSS 10.0): ColdFusion versions 2025.9, 2023.20 and earlier are affected by an Improper Input Validation vulnerability that could…
CVE-2026-48055 — Critical (CVSS 10.0): Streambert is a cross-platform Electron Desktop App to stream and download any video media. In versions 2.4.0 and…
CVE-2026-34910 — Critical (CVSS 10.0): A malicious actor with access to the network could exploit an Improper Input Validation vulnerability found in UniFi OS…
CVE-2026-33587 — Critical (CVSS 10.0): Lack of user input sanitisation in Open Notebook v1.8.3 allows the application user to execute Python code (and…

Browse all CWE-20 (Improper Input Validation) vulnerabilities →