Date: Thu, 2 Feb 2023 22:38:23 +0000 From: Qualys Security Advisory <qsa@...lys.com> To: Georgi Guninski <gguninski@...il.com> CC: "oss-security@...ts.openwall.com" <oss-security@...ts.openwall.com> Subject: Re: double-free vulnerability in OpenSSH server 9.1 Hi Georgi, all, On Thu, Feb 02, 2023 at 09:06:19PM +0200, Georgi Guninski wrote: > Nice find :) > This is very complicated codepath, did a human found it "manually" > or some analysis program found it? Good question! Technically, we did not find the double free: we found the underlying bug in compat_kex_proposal() (the "unintended" free of options.kex_algorithms) during a manual code review, and reported it to the OpenSSH developers in July 2022. Unfortunately, back then we (Qualys) mistakenly believed that "this does not seem to lead to a use-after-free or double-free, but the dangling pointer in options.kex_algorithms is probably not ideal." Then, in January 2023, Mantas Mikulenas reported a double free in sshd to the OpenSSH bugzilla, and we immediately realized that this was a direct consequence of the bug in compat_kex_proposal(). Thank you very much for your mail! With best regards, -- the Qualys Security Advisory team
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