CVE-2009-4444
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…
Does this matter?
EPSS puts the probability of exploitation in the next 30 days at 63.6%, higher than 99% of all known CVEs. Patch or mitigate before the next change window.
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.
- CVSS 2.0
- 6.0 MEDIUMAV:N/AC:M/Au:S/C:P/I:P/A:P
- EPSS
- 63.63% probability · 99th percentile
- Public exploits
- None in Exploit-DB
- CISA KEV
- Not listed
- Affected
- microsoft/internet information services
- Source
- cve@mitre.org
EPSS 63.6% since 26 October 2026; no change recorded yet. The dashed line is the ten per cent mark our analysts treat as “patch before the next change window”. Points are recorded when the score first appears and whenever it moves by a percentage point or more.
References
- http://blogs.technet.com/msrc/archive/2009/12/27/new-reports-of-a-vulnerability-in-iis.aspxBroken Link
- http://secunia.com/advisories/37831Third Party Advisory
- http://securitytracker.com/id?1023387Third Party Advisory, VDB Entry
- http://soroush.secproject.com/downloadable/iis-semicolon-report.pdfThird Party Advisory
- http://www.securityfocus.com/bid/37460Third Party Advisory, VDB Entry
- http://www.vupen.com/english/advisories/2009/3634Third Party Advisory
- http://blogs.technet.com/msrc/archive/2009/12/27/new-reports-of-a-vulnerability-in-iis.aspxBroken Link
- http://secunia.com/advisories/37831Third Party Advisory
- http://securitytracker.com/id?1023387Third Party Advisory, VDB Entry
- http://soroush.secproject.com/downloadable/iis-semicolon-report.pdfThird Party Advisory
- http://www.securityfocus.com/bid/37460Third Party Advisory, VDB Entry
- http://www.vupen.com/english/advisories/2009/3634Third Party Advisory
Source: NVD record, EPSS from FIRST.org, KEV from CISA, exploits from Exploit-DB. Refreshed daily. Download this record as JSON.