Which products and versions are affected by CVE-2009-4444?

Affected: Internet Information Services (Microsoft) versions 5.0, 6.0. The full list is in the CVE brief.

Is CVE-2009-4444 being exploited in the wild?

It is not listed in any known-exploited vulnerabilities catalog.

Is CVE-2009-4444 in the CISA KEV catalog?

No, it is not currently listed in the CISA Known Exploited Vulnerabilities catalog.

Is there a public exploit for CVE-2009-4444?

No public exploit code is known.

Is there a fix for CVE-2009-4444?

No fixed version is listed yet; check the vendor advisory for mitigations.

How urgently should CVE-2009-4444 be patched?

Brandefense priority: patch immediately, because it is very likely to be exploited soon.

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Vulnerability Intelligence

CVE-2009-4444

Medium

Published Dec 29, 2009 · Updated Apr 22, 2026

Key Facts

Patch immediately

CVE-2009-4444 is a medium-severity vulnerability (CVSS 6.0 v2) affecting Internet Information Services (Microsoft).
It is not listed in any known-exploited vulnerabilities catalog. No public exploit code is known.
EPSS estimates a 64% probability of exploitation in the next 30 days.
No fixed version is listed yet; check the vendor advisory for mitigations.
Brandefense priority: patch immediately, because it is very likely to be exploited soon.

CVSS v2

6.0

AV:N/AC:M/Au:S/C:P/I:P/A:P

EPSS (30-day exploit likelihood)

64%

Higher than 99.2% of all scored CVEs

Exploited in the wild

No known

Not in a known-exploited catalog

Public exploit code

None known

Get the full CVE-2009-4444 brief as a PDF

Every affected product and fixed release, exploitation status and a first 24 hours response checklist, emailed within minutes.

Description

Microsoft Internet Information Services (IIS) 5.x and 6.x uses only the portion of a filename before a ; (semicolon) character to determine the file extension, which allows remote attackers to bypass intended extension restrictions of third-party upload applications via a filename with a (1) .asp, (2) .cer, or (3) .asa first extension, followed by a semicolon and a safe extension, as demonstrated by the use of asp.dll to handle a .asp;.jpg file.

Affected Products

2 affected entries in total

Product	Affected versions	Fixed in
Internet Information ServicesMicrosoft	5.0, 6.0	n/a

Timeline

Publicly disclosed
Dec 29, 2009
Last updated
Apr 22, 2026

References

advisory37831
advisory1023387
advisoryhttp://soroush.secproject.com/downloadable/iis-semicolon-report.pdf
advisory37460
advisoryADV-2009-3634

1 more references in the full CVE brief

FAQ

Common Questions.

Microsoft Internet Information Services (IIS) 5.x and 6.x uses only the portion of a filename before a ; (semicolon) character to determine the file extension, which allows remote attackers to bypass intended extension restrictions of third-party upload applications via a filename with a (1) .asp, (2) .cer, or (3) .as…
Affected: Internet Information Services (Microsoft) versions 5.0, 6.0. The full list is in the CVE brief.
It is not listed in any known-exploited vulnerabilities catalog.
No, it is not currently listed in the CISA Known Exploited Vulnerabilities catalog.
No public exploit code is known.
No fixed version is listed yet; check the vendor advisory for mitigations.
Brandefense priority: patch immediately, because it is very likely to be exploited soon.

Is CVE-2009-4444 Running On Your Attack Surface?

Brandefense maps vulnerabilities like this one to your internet-facing assets and tells you exactly where to patch.