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AUSCERT External Security Bulletin Redistribution
ESB-2001.291 -- FreeBSD-SA-01:47.xinetd
xinetd contains multiple vulnerabilities
12 July 2001
AusCERT Security Bulletin Summary
Vendor: FreeBSD Ports Collection
Operating System: FreeBSD
Impact: Denial of Service
Access Required: Remote
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FreeBSD-SA-01:47 Security Advisory
Topic: xinetd contains multiple vulnerabilities
Affects: Ports collection prior to the correction date.
Vendor status: Updated version released
FreeBSD only: NO
xinetd is a replacement for inetd, the internet super-server.
II. Problem Description
The xinetd port, versions prior to xinetd-2.3.0, contains a
potentially exploitable buffer overflow in the logging routines.
If xinetd is configured to log the userid of remote clients obtained
via the RFC1413 ident service, a remote user may be able to cause
xinetd to crash by returning a specially-crafted ident response. This
may also potentially execute arbitrary code as the user running
xinetd, normally root.
In addition, xinetd used a default umask of 0. This may
inadvertently cause applications started by xinetd to create
world-writable files unless the applications explicitely set the
The xinetd 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 5400 third-party applications in a ready-to-install
format. The ports collection shipped with FreeBSD 4.3 is vulnerable
to this problem since it was discovered after its release.
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 be able to cause xinetd to crash and potentially
execute arbitrary code as the user running xinetd.
Processes started by xinetd may inadvertently use a umask of 0, causing
files created by these processes to by world-writable.
If you have not chosen to install the xinetd port/package, then
your system is not vulnerable to this problem.
Deinstall the xinetd port/package if you have installed it.
One of the following:
1) Upgrade your entire ports collection and rebuild the xinetd port.
2) Deinstall the old package and install a new package dated after the
correction date, obtained from the following directories:
Packages are not automatically generated for the alpha architecture at
this time due to lack of build resources.
3) download a new port skeleton for the xinetd 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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