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Date: Sat, 18 May 2013 14:55:57 -0600
From: Kurt Seifried <>
CC: Gilles Chehade <>, "Jason A. Donenfeld" <>,
Subject: Re: Re: CVE Request: DoS in OpenSMTPD TLS Support

Hash: SHA1

On 05/18/2013 10:16 AM, Gilles Chehade wrote:
> Erf...
> Not too nice to send a CVE request without ANY coordination with us
> ...
> Just for the record, you contacted us today reporting a bug which
> could be memory corruption and you didn't know if it could be
> exploited. Then I replied telling you that we discovered and fixed
> the bug two days ago and I then explained to you what the bug
> really was (wrong logic in the IO events handling code in our SSL
> layer). I then told you that we made snapshots with the fix applied
> AND that we has planned for a release on *Monday* with the fixes
> backported.
> The snapshot mail, commit log and diffs makes the issue obvious, I
> just don't understand why you had to go and publish *RIGHT AWAY* a
> script on public lists after our mail exchange...
> I'm not mad that you disclosed a bug, we're very open about it, and
> the git history is full of references to crash and security fixes,
> but it's just REALLY not nice how you handled this and are forcing
> me to do this release in a hurry rather than handling it with
> package maintainers.
> Next time, please coordinate a little, just to be nice.
> On Sat, May 18, 2013 at 04:27:22PM +0200, Jason A. Donenfeld
> wrote:
>> Hi Kurt,
>> The SSL handling in the latest OpenSMTPD (5.3.1) misconfigures
>> its sockets in blocking mode, allowing an attacker to prevent all
>> mail delivery simply by holding a socket open.
>> I discovered this accidentally, as I noticed my HP printer's
>> smtp client would keep the connection indefinitely open after an 
>> unsuccessful authentication attempt, causing no more mail to be 
>> delivered until I SIGKILL'd my smtpd process or unplugged my
>> printer.
>> The following reproduces the attack trivially:
>> #!/usr/bin/env python2 import smtplib import time print "[+]
>> Connecting to server and initiating TLS" smtp =
>> smtplib.SMTP("mail.some-vitim-host.blah", 587) smtp.starttls() 
>> print "[+] No clients will be able to connect as long as this
>> remains open." time.sleep(100000000)
>> Apparently this was fixed recently upstream, noting "evil client"
>> in the commit message: 
A snapshot has been posted to , but
>> no patch release has yet been made.
>> Jason

Please use CVE-2013-2125 for this issue.

- -- 
Kurt Seifried Red Hat Security Response Team (SRT)
PGP: 0x5E267993 A90B F995 7350 148F 66BF 7554 160D 4553 5E26 7993
Version: GnuPG v1.4.13 (GNU/Linux)


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