Date: Sat, 30 Apr 2016 11:52:50 +0200 From: Salvatore Bonaccorso <carnil@...ian.org> To: cve-assign@...re.org Cc: oss-security@...ts.openwall.com Subject: Re: CVE Request: vtun: denial-of-service: high CPU usage after SIGHUP Hi, On Wed, Apr 27, 2016 at 05:58:00PM -0400, cve-assign@...re.org wrote: > -----BEGIN PGP SIGNED MESSAGE----- > Hash: SHA256 > > > 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. You are right -- I cannot think of a situation (or seems hard to find a realistic example) right now where this issue would cross a privilege boundary, and thus might just be considered as bug, but not a vulnerability. Thanks for your feedback, I'm fine to not have assigned an identifier for this. Regards, Salvatore
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