Bug 221459 (CVE-2006-6719)

Summary: CVE-2006-6719 Wget attempts to dereference NULL pointer upon response from malicious FTP server
Product: [Other] Security Response Reporter: Lubomir Kundrak <lkundrak>
Component: vulnerabilityAssignee: Red Hat Product Security <security-response-team>
Status: CLOSED CURRENTRELEASE QA Contact:
Severity: low Docs Contact:
Priority: low    
Version: unspecifiedCC: karsten, psplicha
Target Milestone: ---Keywords: Reopened, Security
Target Release: ---   
Hardware: All   
OS: Linux   
URL: http://www.securityfocus.com/bid/21650
Whiteboard:
Fixed In Version: wget-1.10.2-7.el5 Doc Type: Bug Fix
Doc Text:
Story Points: ---
Clone Of: Environment:
Last Closed: 2009-10-07 08:21:56 UTC Type: ---
Regression: --- Mount Type: ---
Documentation: --- CRM:
Verified Versions: Category: ---
oVirt Team: --- RHEL 7.3 requirements from Atomic Host:
Cloudforms Team: --- Target Upstream Version:
Embargoed:
Attachments:
Description Flags
Reproducer for CVE-2006-6719 wget flaw
none
Patch for CVE-2006-6719 wget flaw none

Description Lubomir Kundrak 2007-01-04 18:24:40 UTC 
Description of problem:

NULL pointer dereference occurs in case a numerical FTP repsonse code
is present, but response text is missing while wget is expecting a reply
to SYST command in ftp-basic.c:ftp_syst().

Version-Release number of selected component (if applicable):

Wget in all supported releases seems to contain the flawed code.

How reproducible:

Allways.

Steps to Reproduce:
1. Run the attached perl script, it listens to localhost:21 by default
2. Attempt to wget ftp://localhost/
  
Actual results:

Wget receives a SIGSEGV.

Expected results:

Wget should save us from the time of trial and deliver us from evil.

Additional info:

Upstream didn't fix the issue yet and for it's fairly simple I doubt
they know about it.
Comment 1 Lubomir Kundrak 2007-01-04 18:24:40 UTC 
Created attachment 144827 [details]
Reproducer for CVE-2006-6719 wget flaw
Comment 2 Lubomir Kundrak 2007-01-04 18:29:20 UTC 
Here's the stack trace:

#0  *__GI___strcasecmp (s1=0x0, s2=0x428a79 "VMS") at strcasecmp.c:65
#1  0x000000000040b6bb in ftp_syst (csock=<value optimized out>,
server_type=0x7fff685d6988) at ftp-basic.c:1041
#2  0x0000000000408a88 in getftp (u=0x83a050, len=0x7fff685d6748, restval=0,
con=0x7fff685d6970) at ftp.c:351
#3  0x0000000000409b58 in ftp_loop_internal (u=0x83a050, f=0x0,
con=0x7fff685d6970) at ftp.c:1173
#4  0x000000000040a01c in ftp_get_listing (u=0x83a050, con=0x7fff685d6970,
f=0x7fff685d69a8) at ftp.c:1317
#5  0x000000000040a553 in ftp_loop (u=0x83a050, dt=0x7fff685d6bb0, proxy=<value
optimized out>, recursive=false, glob=false) at ftp.c:1798
#6  0x000000000041eab7 in retrieve_url (origurl=0x83a0c0 "ftp://localhost/",
file=0x7fff685d6ba8, newloc=0x7fff685d6ba0, refurl=0x0, dt=0x7fff685d6bb0,
    recursive=false) at retr.c:691
#7  0x000000000041a740 in main (argc=2, argv=0x7fff685d6cd8) at main.c:961
#8  0x0000003def81da44 in __libc_start_main (main=0x41a050 <main>, argc=2,
ubp_av=0x7fff685d6cd8, init=<value optimized out>, fini=<value optimized out>,
    rtld_fini=<value optimized out>, stack_end=0x7fff685d6cc8) at libc-start.c:231
#9  0x00000000004039b9 in _start ()

And the relevand faulty code:

1033
1034      /* Skip the number (215, but 200 (!!!) in case of VMS) */
1035      strtok (respline, " ");
1036
1037      /* Which system type has been reported (we are interested just in the
1038         first word of the server response)?  */
1039      request = strtok (NULL, " ");

Here request gets set to NULL, as there are no more tokens in the reponse

1040
1041      if (!strcasecmp (request, "VMS"))

And here we compare the NULL string

1042        *server_type = ST_VMS;
1043      else if (!strcasecmp (request, "UNIX"))
1044        *server_type = ST_UNIX;
Comment 3 Lubomir Kundrak 2007-01-04 18:44:38 UTC 
Created attachment 144828 [details]
Patch for CVE-2006-6719 wget flaw

And, because it's Christmas, here's the patch for you.
And please report upstream.
Comment 6 Tomas Hoger 2009-10-07 08:21:56 UTC 
This issue was reviewed by the Red Hat Security Response Team.  Impact of is is limited to a not exploitable application crash caused by a NULL pointer dereference.  When using wget to download files from untrusted and malicious FTP server, or when an attacker is able to modify communication stream with the trusted FTP server, harmless crash has lesser impact than e.g. downloading (and executing) some malware.

This bug was addressed in wget packages in Red Hat Enterprise Linux 5 before the initial released.  It affects wget versions in Red Hat Enterprise Linux 3 and 4, but there's no plan to address it via security update.