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AUSCERT External Security Bulletin Redistribution
ESB-2000.321 -- FreeBSD-SA-00:60
boa web server allows arbitrary file access/execution
31 October 2000
AusCERT Security Bulletin Summary
Vendor: FreeBSD Ports Collection
Operating System: FreeBSD
Impact: Read-only Data Access
Execute Arbitrary Code/Commands
Access Required: Remote
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FreeBSD-SA-00:60 Security Advisory
Topic: boa web server allows arbitrary file access/execution
Credits: Lluis Mora <llmora@S21SEC.COM>
Affects: Ports collection prior to the correction date.
Vendor status: Updated version released
FreeBSD only: NO
Boa is a high-performance web server.
II. Problem Description
The boa port, versions after 0.92 but prior to 0.94.8.3, contains a
vulnerability which allows remote users to view arbitrary files
outside the document root. The vulnerability is that boa does not
correctly restrict URL-encoded requests containing ".." in the path.
In addition, if the administrator has enabled CGI extension support, a
request for any file ending in .cgi will result in the file being
executed with the privileges of the user id running the web server.
Since the .cgi file may reside outside the document root, this may
result in untrusted binaries/scripts being executed. If an attacker
can upload files to the system, e.g. via anonymous FTP, they can cause
arbitrary code to be executed by the user running the web server.
The boa port is not installed by default, nor is it "part of FreeBSD"
as such: it is part of the FreeBSD ports collection, which contains
over 4000 third-party applications in a ready-to-install format.
The ports collections shipped with FreeBSD 3.5.1 and 4.1.1 contain
this problem since it was discovered after the releases.
FreeBSD makes no claim about the security of these third-party
applications, although an effort is underway to provide a security
audit of the most security-critical ports.
Remote users may view any file on the system that is accessible by the
webserver account. In addition, the webserver account may be
compromised due to the execution of arbitrary files outside the
If you have not chosen to install the boa port/package, then your
system is not vulnerable to this problem.
Deinstall the boa port/package, if you you have installed it.
One of the following:
1) Upgrade your entire ports collection and rebuild the boa port.
2) Deinstall the old package and install a new package dated after the
correction date, obtained from:
3) download a new port skeleton for the cvsweb port from:
and use it to rebuild the port.
4) Use the portcheckout utility to automate option (3) above. The
portcheckout port is available in /usr/ports/devel/portcheckout or the
package can be obtained from:
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