Re: CVE Request: vtun: denial-of-service: high CPU usage after SIGHUP

[cve-assign () mitre org]

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> https://bugs.debian.org/818489

Can you describe how this crosses a privilege boundary?


> > When you send a SIGHUP to a vtun client process and it cannot connects
> > to the remote server, vtun try to reconnect without sleep between each attempt.
> > In result, the vtun process uses lot of CPU, and write to syslog without limit.

Is there an important way in which this differs from "The vtun client
is not installed. The attacker simply writes their own program to
reconnect without sleeping and make many syslog calls"?

For example: does vtun's resource consumption belong to the root
account in a common scenario, but SIGHUP is accepted from an
unprivileged user? Are different unprivileged users successfully
sending SIGHUP to one another's vtun client processes? Do you mean
that there's a potentially common attack pattern in which a
man-in-the-middle attacker intentionally blocks connections to the
remote server in order to trick the victim into sending a SIGHUP, and
(in some sense) this man-in-the-middle attacker is thereby able to
trigger the excessive resource consumption?

Sometimes there are CVE IDs for "a client application inadvertently
starts launching a network DoS attack" but this is typically only in
cases where someone can send forged packets to the client application
in order to start the attack.

- -- 
CVE Assignment Team
M/S M300, 202 Burlington Road, Bedford, MA 01730 USA
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