Bug 514957 (CVE-2009-2694)

Summary: CVE-2009-2694 pidgin: insufficient input validation in msn_slplink_process_msg()
Product: [Other] Security Response Reporter: Tomas Hoger <thoger>
Component: vulnerabilityAssignee: Red Hat Product Security <security-response-team>
Status: CLOSED ERRATA QA Contact:
Severity: urgent Docs Contact:
Priority: urgent    
Version: unspecifiedCC: bressers, jlieskov, kreilly, rcvalle, wtogami
Target Milestone: ---Keywords: Security
Target Release: ---   
Hardware: All   
OS: Linux   
Whiteboard: impact=critical,source=upstream,reported=20090731,public=20090818,cvss2=7.5/AV:N/AC:L/Au:N/C:P/I:P/A:P,cwe=CWE-228->CWE-119
Fixed In Version: Doc Type: Bug Fix
Doc Text:
Story Points: ---
Clone Of: Environment:
Last Closed: 2009-08-24 03:32:28 EDT Type: ---
Regression: --- Mount Type: ---
Documentation: --- CRM:
Verified Versions: Category: ---
oVirt Team: --- RHEL 7.3 requirements from Atomic Host:
Cloudforms Team: ---
Bug Depends On: 515723, 515724, 515725, 515726, 515727, 833961    
Bug Blocks:    

Description Tomas Hoger 2009-07-31 12:22:16 EDT
Core Security Technologies reported that previous upstream fixes addressing insufficient input validation flaw in pidgin / libpurple in function msn_slplink_process_msg() are inefficient and can be bypassed.  This flaw allows an attacker to overwrite pidgin's memory and possibly execute arbitrary code with the privileges of the user running application using libpurple.

This issue was previously tracked as CVE-2008-2927 (bug #453764) and CVE-2009-1376 (bug #500493, incomplete fix).
Comment 4 Tomas Hoger 2009-08-13 08:31:56 EDT

Users can lower the impact of this flaw by making sure their privacy settings only allow Pidgin to accept messages from the users on their buddy list.  This will prevent exploitation of this flaw by other random MSN users.
Comment 5 Tomas Hoger 2009-08-13 08:39:01 EDT
Technically, this is not really an incomplete fix of the previous integer overflow issues, rather a new issue affecting same code part as previous issues.

In the new attack, attacker aims to exploit a NULL pointer dereference flaw.  This is achieved by sending message with non-0 offset.  When such message is processed in msn_slplink_process_msg(), msn_slplink_message_find() is called to find previous parts of the message sent within the same session.  With specially crafted previous messages, msn_slplink_message_find() may return a structure for ACK message, rather than request message, that later triggers NULL pointer dereference in:

  memcpy(slpmsg->buffer + offset, data, len);

In ACK message, slpmsg->buffer is NULL and attacker supplied offset can be used to control what memory area will be overwritten.
Comment 8 errata-xmlrpc 2009-08-18 14:00:57 EDT
This issue has been addressed in following products:

  Red Hat Enterprise Linux 3
  Red Hat Enterprise Linux 4
  Red Hat Enterprise Linux 5

Via RHSA-2009:1218 https://rhn.redhat.com/errata/RHSA-2009-1218.html
Comment 9 Jan Lieskovsky 2009-08-21 04:58:49 EDT
MITRE's CVE-2009-2694 record:

The msn_slplink_process_msg function in
libpurple/protocols/msn/slplink.c in libpurple, as used in Pidgin
(formerly Gaim) before 2.5.9 and Adium 1.3.5 and earlier, allows
remote attackers to execute arbitrary code or cause a denial of
service (memory corruption and application crash) by sending multiple
crafted SLP (aka MSNSLP) messages to trigger an overwrite of an
arbitrary memory location. NOTE: this issue reportedly exists because
of an incomplete fix for CVE-2009-1376.

Comment 10 Tomas Hoger 2009-08-24 03:32:28 EDT
All current Fedora versions are now updated to 2.6.0+ too.