oss-security - [ADVISORY] LLDP underflow while parsing malformed Auto Attach TLV (Open vSwitch)

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Date: Tue, 20 Dec 2022 22:39:23 +0100
From: Ilya Maximets <i.maximets@....org>
To: oss-security@...ts.openwall.com, ovs-announce@...nvswitch.org,
 ovs-discuss <ovs-discuss@...nvswitch.org>
Cc: i.maximets@....org, Aaron Conole <aconole@...hat.com>,
 Qian Chen <cq674350529@...il.com>
Subject: [ADVISORY] LLDP underflow while parsing malformed Auto Attach TLV
 (Open vSwitch)

Description
===========

Multiple versions of Open vSwitch are vulnerable to crafted LLDP
packets causing denial of service, and data underflow attacks.
Triggering the vulnerabilities requires LLDP processing to be enabled
for a specific port.  Open vSwitch versions prior to 2.4.0 are not
vulnerable.

The Common Vulnerabilities and Exposures project (cve.mitre.org)
did not assign the identifier to this issue yet.  The identifier will
be communicated separately.  This issue does not affect the `lldpd'
project, although they share a code base.  The issue is related to
parsing the Auto Attach TLVs, which is specific to the Open vSwitch
implementation.

Mitigation
==========

For any version of Open vSwitch, preventing LLDP packets from reaching
Open vSwitch mitigates the vulnerability.  We do not recommend
attempting to mitigate the vulnerability this way because of the
following difficulties:

    - Open vSwitch obtains packets before the iptables host firewall,
      so ebtables on the Open vSwitch host cannot ordinarily block the
      vulnerability.

    - If Open vSwitch is configured to receive and transmit LLDP
      messages, the required functionality will need to be disabled
      potentially disrupting the network.

We have found that Open vSwitch is subject to a denial of service, and
possibly a remote code execution exploit when LLDP processing is enabled
on an interface.  By default, interfaces are not configured to process
LLDP messages.

Fix
===

Patches to fix these vulnerabilities in Open vSwitch 2.13.x and newer are
applied to the appropriate branches, and the original patch is located
at:

   https://mail.openvswitch.org/pipermail/ovs-dev/2022-December/400596.html

Recommendation
==============

We recommend that users of Open vSwitch apply the respective patch, or
upgrade to a known patched version of Open vSwitch.  These include:

* 3.0.3
* 2.17.5
* 2.16.6
* 2.15.7
* 2.14.8
* 2.13.10

Acknowledgments
===============

The Open vSwitch team wishes to thank the reporter:

  Qian Chen <cq674350529@...il.com>

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