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AUSCERT External Security Bulletin Redistribution
ESB-2000.097 -- FreeBSD-SA-00:08 [REVISED]
Lynx ports contain numerous buffer overflows
18 May 2000
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AusCERT Security Bulletin Summary
---------------------------------
Product: lynx
Vendor: FreeBSD
Operating System: FreeBSD
Unix
Platform: N/A
Impact: Execute Arbitrary Code
Access Required: Remote
Ref: ESB-2000.048
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FreeBSD-SA-00:08 Security Advisory
FreeBSD, Inc.
Topic: Lynx ports contain numerous buffer overflows
Category: ports
Module: lynx/lynx-current/lynx-ssl/ja-lynx/ja-lynx-current
Announced: 2000-03-15
Revised: 2000-05-17
Affects: Ports collection before the correction date.
Corrected: 2000-04-16 [lynx-current]
2000-04-21 [lynx]
FreeBSD only: NO
I. Background
Lynx is a popular text-mode WWW browser, available in several versions
including SSL support and Japanese language localization.
II. Problem Description
Versions of the lynx software prior to version 2.8.3pre.5 were written
in a very insecure style and contain 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 3200 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.
III. Impact
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.
IV. Workaround
Remove the lynx/lynx-current/lynx-ssl/ja-lynx/ja-lynx-current ports,
if you you have installed them.
V. Solution
Upgrade to lynx or lynx-current after the correction date.
After the initial release of this advisory, the Lynx development team
conducted an audit of the source code, and have corrected the known
vulnerabilities in lynx as well as increasing the robustness of the
string-handling code. As of lynx-2.8.3pre.5, we consider it safe
enough to use again.
Note that there may be undiscovered vulnerabilities remaining in the
code, as with all software - but should any further vulnerabilities be
discovered a new advisory will be issued.
At this time the lynx-ssl/ja-lynx/ja-lynx-current ports are not yet
updated to a safe version of lynx: this advisory will be reissued
again once they are.
1) Upgrade your entire ports collection and rebuild the lynx or
lynx-current port.
2) Reinstall a lynx new package dated after the correction date,
obtained from:
ftp://ftp.FreeBSD.org/pub/FreeBSD/ports/i386/packages-3-stable/www/lynx-2.8.3.1.tgz
ftp://ftp.FreeBSD.org/pub/FreeBSD/ports/i386/packages-4-stable/www/lynx-2.8.3.1.tgz
ftp://ftp.FreeBSD.org/pub/FreeBSD/ports/alpha/packages-4-stable/www/lynx-2.8.3.1.tgz
ftp://ftp.FreeBSD.org/pub/FreeBSD/ports/i386/packages-5-current/www/lynx-2.8.3.1.tgz
ftp://ftp.FreeBSD.org/pub/FreeBSD/ports/alpha/packages-5-current/www/lynx-2.8.3.1.tgz
Note that the lynx-current port is not automatically built as a package.
3) download a new port skeleton for the lynx/lynx-current port from:
http://www.freebsd.org/ports/
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:
ftp://ftp.freebsd.org/pub/FreeBSD/ports/packages/devel/portcheckout-1.0.tgz
VI. Revision History
v1.0 2000-03-15 Initial release
v1.1 2000-05-17 Update to note fix of lynx and lynx-current ports.
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