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Date: Wed, 1 Feb 2017 20:35:01 +0100
From: Bálint Réczey <balint@...intreczey.hu>
To: oss-security@...ts.openwall.com
Subject: CVE request: Use after free in libmysqlclient.so (was: Re: Use after
 free in libmysqlclient.so)

Hi,

I'm adjusting the subject to reflect the content in case the request
was accidentally missed.

Thanks for the report!

Cheers,
Balint

2017-01-27 23:53 GMT+01:00  <pali@...n.org>:
> Hello, I would like to report problem related to MySQL/MariaDB and
> possibly asking for assigning CVE if this list is the right place.
>
> C client library for MySQL (libmysqlclient.so) has use-after-free defect
> which can cause crash of applications using that MySQL client.
>
> Defect occurs by calling mysql_close() function from libmysqlclient.so.
> If mysql_close() is called before calling all mysql_stmt_close() (for
> all allocated stmts), then following mysql_stmt_close() call try to
> write to already released memory. mysql_close() let dangling pointer
> exist for prepared statements. Real problem is in function
> mysql_prune_stmt_list() which incorrectly iterate over elements.
> Function list_add() overwrite ->next pointer of current element which
> overwrite next element for iteration.
>
> Basically it is just wrong usage of linked list structure.
>
> Languages in which is not guaranteed order of executing destructor of
> created objects have a big problem as such writing to memory pointed by
> dangling can cause crash of whole application.
>
> E.g. libmysqlclient.so used by perl DBD::mysql driver cause crash of
> whole perl process with simple script:
>
> perl -MDBI -e '
> $dbh = DBI->connect("dbi:mysql:", "root", undef,
>                     {RaiseError => 1, mysql_server_prepare => 1});
> $sth1 = $dbh->prepare("SELECT 1");
> $sth2 = $dbh->prepare("USE mysql");
> $dbh->disconnect;
> $dbh = undef;
> '
> Segmentation fault
>
> Tested on amd64 Ubuntu 12.04 LTS with perl 5.14.2. To reproduce change
> username, password and host where is running mysql server. Valgrind can
> prove that memory corruption really occurs.
>
> This defect was fixed in MySQL 5.6.21 and MySQL 5.7.5 releases. But is
> present in all MySQL 5.5 versions (and also older) and appropriate older
> 5.6 and 5.7 versions. MySQL 5.5 is still used, supported and included in
> lot of linux distributions.
>
> Moreover this defect is present also in MariaDB releases. I tested all
> last major versions 10.2.3, 10.1.21, 10.0.29, 5.5.54 and all those are
> affected.
>
> MySQL and MariaDB provides also standalone package with only C client
> library libmysqlclient.so (without server) under name "Connector/C" and
> so appropriate versions of it are affected too.
>
> I found that this defected was fixed in MySQL git repository by commit:
> https://github.com/mysql/mysql-server/commit/4797ea0b772d5f4c5889bc552424132806f46e93
>
> That commit can be easily applied to last MySQL 5.5.54 version and fixes
> this defect.
>
> Looks like problem was already reported and is publically available in
> MySQL bug tracker, see more details on links:
> https://bugs.mysql.com/bug.php?id=70429
> https://bugs.mysql.com/bug.php?id=63363
> (tickets are closed despite fact that MySQL 5.5 and older are not fixed)
>
> ---
>
> I reported this problem to Oracle secalert_us@...cle.com two months ago,
> but they did absolutely nothing for fixing it in MySQL 5.5. Instead they
> started resending this problem to some random people with @cpan.org
> address for unknown reason. And told me to not disclose information
> about this defect. Resending does not look like normal handling of
> security related problem! Therefore I suggest other people to not
> wasting time reporting problems to Oracle for open source applications.
>
> As two months is really long time to fix such problem which was already
> fixed in new versions; it is already publically disclosed in MySQL bug
> tracker; fix available in public git; problem is in major MariaDB
> versions; fix is small; and this is open source product included in many
> linux distributions I decided to send information to oss-security.

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