Bug 201335 - CVE-2006-1168 Possibility to underflow a .bss buffer with attacker controlled data
Summary: CVE-2006-1168 Possibility to underflow a .bss buffer with attacker controlled...
Alias: None
Product: Red Hat Enterprise Linux 4
Classification: Red Hat
Component: ncompress
Version: 4.0
Hardware: All
OS: Linux
Target Milestone: ---
: ---
Assignee: Peter Vrabec
QA Contact: Ben Levenson
Whiteboard: impact=low,source=vendorsec,reported=...
Depends On:
Blocks: CVE-2006-1168
TreeView+ depends on / blocked
Reported: 2006-08-04 14:02 UTC by Marcel Holtmann
Modified: 2011-08-17 17:00 UTC (History)
2 users (show)

Fixed In Version: RHSA-2006-0663
Doc Type: Release Note
Doc Text:
Clone Of:
Last Closed: 2006-09-12 16:47:29 UTC
Target Upstream Version:

Attachments (Terms of Use)
fix candidate (533 bytes, patch)
2006-08-10 10:03 UTC, Peter Vrabec
no flags Details | Diff

System ID Priority Status Summary Last Updated
Red Hat Product Errata RHSA-2006:0663 normal SHIPPED_LIVE Low: ncompress security update 2006-09-12 04:00:00 UTC

Description Marcel Holtmann 2006-08-04 14:02:31 UTC
Report from Tavis Ormandy, Google Security Team:

An audit of ncompress version 4.2.4 uncovered a serious security flaw, this loop
in decompress() (~1749, compress42.c) performs no bounds checking, allowing a
specially crafted datastream to underflow a .bss buffer with attacker controlled
data. Some research reveals that the lzw decompressors from gzip and openbsd
(both derived from the same public domain implementation) have already corrected
this flaw, however ncompress shipped by (at least) gentoo, debian, fedora and
suse seem to still be vulnerable.

              while ((cmp_code_int)code >= (cmp_code_int)256)
              { /* Generate output characters in reverse order */
                  *--stackp = tab_suffixof(code);
                  code = tab_prefixof(code);

In my test environment I've been able to successfully overwirte .got and .dtors
with controlled data. The most simple testcase would be:

$ perl -e 'print "\x1f\x9d\x90","\x01"x"2048"' | compress -d

My suggested fix would be adding  `&& stackp >= htabof(0)` to the loop condition.

Comment 1 Peter Vrabec 2006-08-10 10:03:33 UTC
Created attachment 133926 [details]
fix candidate

I'd like to use this patch, which is based on fix extracted from gzip.

Comment 13 Red Hat Bugzilla 2006-09-12 16:47:29 UTC
An advisory has been issued which should help the problem
described in this bug report. This report is therefore being
closed with a resolution of ERRATA. For more information
on the solution and/or where to find the updated files,
please follow the link below. You may reopen this bug report
if the solution does not work for you.


Note You need to log in before you can comment on or make changes to this bug.