Re: a DoS vulnerability associated with conflated Message-IDs?

Subject: Re: a DoS vulnerability associated with conflated Message-IDs?

Date: Sat, 30 Jul 2022 09:41:41 -0300

To: Daniel Kahn Gillmor, Peter Wang, notmuch mailing list


From: David Bremner

Daniel Kahn Gillmor <> writes:

> On Fri 2017-08-04 16:42:54 -0400, David Bremner wrote:
>> Peter Wang <> writes:
>>> On Thu, 08 Mar 2012 11:37:09 -0500, Daniel Kahn Gillmor <> wrote:
>>>> notmuch currently treats all messages with the same Message-ID as
>>>> the same message.  I think this could be a vulnerability :(
>>>> If two messages have the same Message-ID, is there a guarantee of which
>>>> of these messages will be produced during a notmuch show?
>>>> Either way, it seems to create a potential DoS attack on notmuch users.
>>> Yesterday I was expecting a confirmation message which, seemingly, never
>>> came.  It turns out my maildir already contained a message from the
>>> same system.  From three years ago.  With the same Message-ID.
>>> Malice has nothing on incompetence.
>>> Could we distinguish messages with identical Message-IDs based on
>>> some header fields, e.g. Date, From?
>> I wouldn't say this problem is fixed, but we are making some
>> progress. In master all copies of the file are now indexed. It still
>> needs various UI work before we can consider the problem really fixed,
>> but it is now technically possible to detect such an attack (since the
>> "good terms" are also indexed).
> otoh, we now enable some additional (perhaps weirder) attacks, like:
>  * i can make someone else's mail show up in your mailbox with a search
>    term of my choosing by sending you a new mail co-opting their
>    message-id.
> we definitely need some UI for dealing with this, and perhaps some
> explicit de-duping logic or maintenance scripts would be useful too.
>    --dkg

There is now a simple UI for dealing with duplicate messages in the
emacs UI (as of commit 1ef7c75111b84ea19af3186ddc12f2ba434c93de, which
should be part of 0.37). 
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