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AUSCERT External Security Bulletin Redistribution
ESB-2000.048 -- FreeBSD-SA-00:08
Lynx ports contain numerous buffer overflows
20 March 2000
The FreeBSD Security Team has released the following security advisory
describing vulnerabilities in the Lynx Web Browser. A malicious web server
may exploit these vulnerabilities in a visiting user's lynx browser which
may allow execution of arbitrary code as the visiting user on the user's
The FreeBSD Security Team recommends removal of the Lynx package if
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FreeBSD-SA-00:08 Security Advisory
Topic: Lynx ports contain numerous buffer overflows
Affects: Ports collection before the correction date.
Corrected: See below.
FreeBSD only: NO
Lynx is a popular text-mode WWW browser, available in several versions
including SSL support and Japanese language localization.
II. Problem Description
The lynx software is written in a very insecure style and contains numerous
potential and several proven security vulnerabilities (publicized on the
BugTraq mailing list) exploitable by a malicious server.
The lynx ports are not installed by default, nor are they "part of FreeBSD"
as such: they are part of the FreeBSD ports collection, which contains over
3100 third-party applications in a ready-to-install format.
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.
A malicious server which is visited by a user with the lynx browser can
exploit the browser security holes in order to execute arbitrary code as
the local user.
If you have not chosen to install any of the
lynx/lynx-current/lynx-ssl/ja-lynx/ja-lynx-current ports/packages, then
your system is not vulnerable.
Remove the lynx/lynx-current/lynx-ssl/ja-lynx/ja-lynx-current ports, if you
you have installed them.
Unfortunately, there is no simple fix to the security problems with the
lynx code: it will require a full review by the lynx development team and
recoding of the affected sections with a more security-conscious attitude.
In the meantime, there are two other text-mode WWW browsers available in
FreeBSD ports: www/w3m (also available in www/w3m-ssl for an SSL-enabled
version, and japanese/w3m for Japanese-localization) and www/links.
Note that the FreeBSD Security Officer does not make any recommendation
about the security of these two browsers - in particular, they both appear
to contain potential security risks, and a full audit has not been
performed, but at present no proven security holes are known. User beware -
please watch for future security advisories which will publicize any such
vulnerabilities discovered in these ports.
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