NSFOCUS Security Advisory(SA2001-07)

Topic: ActivePerl PerlIS.dll Remote Buffer Overflow Vulnerability

Release DateЈє 2001-11-15

CVE CAN ID : CAN-2001-0815
BUGTRAQ ID : 3526

Affected system:

Activestate ActivePerl 5.6.1.629 and earlier versions

• Microsoft IIS 4.0
• Microsoft IIS 5.0

Not affected system:

Activestate ActivePerl 5.6.1.630

• Microsoft IIS 4.0
• Microsoft IIS 5.0

Impact:

NSFOCUS Security Team has found a exploited buffer overflow vulnerability in
a dynamic link library (perlIS.dll) of ActivePerl when handling overlong
filename. Exploit of it, an attacker could remotely execute arbitrary code.

DescriptionЈє

ActivePerl is a binary package of perl for Linux, Solaris or Windows system
developed by ActiveState. ActivePerl for windows has a dynamic link library,
perlIS.dll, which is a ISAPI extension to provide high-performance perl
interface for Microsoft IIS server.

PerlIS.dl was discovered to handle perl script request sent by user without
correct length check of the URL. In case that an attacker send an overlong URL
request, PerlIS would call strcpy() and copy it to a stack buffer, which would
trigger a buffer overflow. Attacker could overwrite some sensitive data in the
stack like returned address. With well-crafted URL request, the attacker might
be able to execute arbitrary code remotely.

Exploiting this vulnerability successfully, an attack might access
IWAM_machinename account in IIS 5.0 and Local SYSTEM privilege in IIS 4.0.

Exploit:

$ lynx http://host/cgi-bin/`perl -e 'print "A" x 360'`.pl

The remote procedure call failed.

Workaround:

Edit "perlIS.dll" ISAPI extension in Internet Service Manager and check "Check
that file exists" option.

Vendor Status:

2001.10.15 We reported this vulnerability to ActiveState.
2001.10.23 ActiveState informed that the vulnerability has been eliminated in
build 630.

Latest version of ActivePerl is available at

http://www.activestate.com/Products/ActivePerl/download.plex

Additional Information:

The Common Vulnerabilities and Exposures (CVE) project has
assigned the name CAN-2001-0815 to this issue. This is a
candidate for inclusion in the CVE list (http://cve.mitre.org),
which standardizes names for security problems. Candidates
may change significantly before they become official CVE entries.

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NSFOCUS Security Team <[email protected]>
NSFOCUS INFORMATION TECHNOLOGY CO.,LTD
(http://www.nsfocus.com)