[AJECT] Softalk IMAP Server 8.5.1 DoS vulnerability

[João Antunes <jantunes () di fc ul pt>]

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Synopsis
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Softalk IMAP Server 8.5.1 is vulnerable to denial-of-service (DoS)  
attacks.
The IMAP server crashes when processing an APPEND command with a  
strange parameter (see details bellow). Other commands may also  
trigger the same behavior.

Product: Softalk Mail Server
Version: 8.5.1.431 and probably the older versions
Vendor: Softalk (www.softalkltd.com)
Type: Denial-of-service
Risk: service disruption
Remote: Yes
Discovered by: João Antunes (AJECT -- Attack Injection Tool) on 05/Jun/ 
2008
Exploit: Not Available
Solution: Not Available
Status: Developers were contacted and should be releasing a corrected  
version soon (8.5.2 beta 2)

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Vulnerability Description
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The vulnerability can be triggered by sending the following messages  
to the imap server:
A001 LOGIN user password
A01 APPEND Ax5000 (UIDNEXT MESSAGES) (…) Ax5000 (UIDNEXT MESSAGES)

For the sake of legibility, the APPEND command was presented above in  
a condensed form.
The "(...)" means that the parameters should be repeated several times  
in the same command (e.g., ten times). Successful exploitation results  
in a remote denial of service.