[squid-announce] [ADVISORY] SQUID-2019:12 Multiple issues in ESI Response processing
squid3 at treenet.co.nz
Thu Apr 23 09:03:07 UTC 2020
Squid Proxy Cache Security Update Advisory SQUID-2019:12
Advisory ID: SQUID-2019:12
Date: April 23, 2020
Summary: Multiple issues
in ESI Response processing.
Affected versions: Squid 3.x -> 3.5.28
Squid 4.x -> 4.10
Squid 5.x -> 5.0.1
Fixed in version: Squid 4.11 and 5.0.2
Due to incorrect buffer handling Squid is vulnerable to cache
poisoning, remote execution, and denial of service attacks when
processing ESI responses.
These problems allow a remote server delivering certain ESI
response syntax to trigger a buffer overflow.
On systems with heap overflow protection overflow will shutdown
the proxy causing a denial of service for all clients accessing
the Squid service.
On systems with ESI buffer pooling (the default) overflow will
truncate portions of generated payloads. Poisoning the HTTP
response cache with corrupted objects.
The CVE-2019-12519 issue also overwrites arbitrary attacker
controlled information onto the process stack. Allowing remote
code execution with certain crafted ESI payloads.
These problems are restricted to ESI responses received from an
upstream server. Attackers have to compromise the server or
transmission channel to utilize these vulnerabilities.
This bug is fixed by Squid versions 4.11 and 5.0.2.
In addition, patches addressing this problem for the stable
releases can be found in our patch archives:
If you are using a prepackaged version of Squid then please refer
to the package vendor for availability information on updated
Determining if your version is vulnerable:
All Squid-2.x are not vulnerable.
All Squid built with --disable-esi are not vulnerable.
All Squid-3.0 versions built without --enable-esi are not
All Squid-3.x versions built with --enable-esi are vulnerable.
All Squid-4.x up to and including Squid-4.10 are vulnerable.
Squid-5.0.1 is not vulnerable to the CVE-2019-12519 remote code
Squid-5.0.1 is vulnerable to the CVE-2019-12521 issues.
Build Squid with --disable-esi
Contact details for the Squid project:
For installation / upgrade support on binary packaged versions
of Squid: Your first point of contact should be your binary
If your install and build Squid from the original Squid sources
then the squid-users at lists.squid-cache.org mailing list is your
primary support point. For subscription details see
For reporting of non-security bugs in the latest STABLE release
the squid bugzilla database should be used
For reporting of security sensitive bugs send an email to the
squid-bugs at lists.squid-cache.org mailing list. It's a closed
list (though anyone can post) and security related bug reports
are treated in confidence until the impact has been established.
This vulnerability was discovered by Jeriko One
<jeriko.one at gmx.us>.
Fixed by Amos Jeffries of Treehouse Networks Ltd.
2019-05-14 14:56:49 UTC Initial Report
2019-05-20 11:23:13 UTC Patches Released
2019-06-05 15:52:17 UTC CVE Assignment
2020-04-23 08:00:00 UTC Advisory Released
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