How severe is CVE-2009-1135?

CVE-2009-1135 has a CVSS 2.0 base score of 9.0, rated critical severity.

Is CVE-2009-1135 being actively exploited?

It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 26% (98th percentile), an estimate of the probability of exploitation in the next 30 days.

What products are affected by CVE-2009-1135?

CVE-2009-1135 primarily affects Microsoft Isa Server. In total, 3 product configurations (CPEs) are listed as vulnerable; see the affected-products list for the exact versions.

How do I fix CVE-2009-1135?

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-2009-1135 published?

CVE-2009-1135 was published on 2009-07-15 and last updated on 2026-06-16.

CVE-2009-1135

CVE-2009-1135 is a critical-severity vulnerability in Microsoft Isa Server with a CVSS 2.0 base score of 9.0. Its EPSS exploit-prediction score of 26% places it in the 98th percentile, indicating an elevated likelihood of exploitation. The underlying weakness is classified as CWE-264.

Key facts

Severity: Critical (CVSS 2.0 base score 9.0)
EPSS exploit prediction: 26% (98th percentile)
Actively exploited: Not listed in CISA KEV
Weakness: CWE-264
Affected product: Microsoft Isa Server
Published: 2009-07-15
Last modified: 2026-06-16

Description

Microsoft Internet Security and Acceleration (ISA) Server 2006 Gold and SP1, when Radius OTP is enabled, uses the HTTP-Basic authentication method, which allows remote attackers to gain the privileges of an arbitrary account, and access published web pages, via vectors involving attempted access to a network resource behind the ISA Server, aka "Radius OTP Bypass Vulnerability."

Frequently asked questions

What is CVE-2009-1135?: Microsoft Internet Security and Acceleration (ISA) Server 2006 Gold and SP1, when Radius OTP is enabled, uses the HTTP-Basic authentication method, which allows remote attackers to gain the privileges of an arbitrary account, and access published web pages, via vectors involving attempted access to a network resource behind the ISA Server, aka "Radius OTP Bypass Vulnerability."
How severe is CVE-2009-1135?: CVE-2009-1135 has a CVSS 2.0 base score of 9.0, rated critical severity.
Is CVE-2009-1135 being actively exploited?: It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 26% (98th percentile), an estimate of the probability of exploitation in the next 30 days.
What products are affected by CVE-2009-1135?: CVE-2009-1135 primarily affects Microsoft Isa Server. In total, 3 product configurations (CPEs) are listed as vulnerable; see the affected-products list for the exact versions.
How do I fix CVE-2009-1135?: 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-2009-1135 published?: CVE-2009-1135 was published on 2009-07-15 and last updated on 2026-06-16.

References

Affected products (3)

cpe:2.3:a:microsoft:isa_server:2006:*:*:*:*:*:*:*
cpe:2.3:a:microsoft:isa_server:2006:sp1:*:*:*:*:*:*
cpe:2.3:a:microsoft:isa_server:2006:supportability:*:*:*:*:*:*

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