A vulnerability, which was classified as problematic, has been found in Open vSwitch up to 2.7.6. This issue affects the function ofproto_rule_insert__ of the file ofproto/ofproto.c. The manipulation as part of a Commit leads to a input validation vulnerability. Using CWE to declare the problem leads to CWE-20. The product receives input or data, but it does not validate or incorrectly validates that the input has the properties that are required to process the data safely and correctly. Impacted is availability. The summary by CVE is:

An issue was discovered in Open vSwitch (OvS) 2.7.x through 2.7.6, affecting ofproto_rule_insert__ in ofproto/ofproto.c. During bundle commit, flows that are added in a bundle are applied to ofproto in order. If a flow cannot be added (e.g., the flow action is a go-to for a group id that does not exist), OvS tries to revert back all previous flows that were successfully applied from the same bundle. This is possible since OvS maintains list of old flows that were replaced by flows from the bundle. While reinserting old flows, OvS has an assertion failure due to a check on rule state != RULE_INITIALIZED. This would work for new flows, but for an old flow the rule state is RULE_REMOVED. The assertion failure causes an OvS crash.

The bug was discovered 06/17/2018. The weakness was published 09/19/2018 (Website). The advisory is shared at github.com. The identification of this vulnerability is CVE-2018-17205 since 09/19/2018. The exploitation is known to be easy. The attack may be initiated remotely. No form of authentication is needed for a successful exploitation. Technical details are known, but no exploit is available.

The vulnerability was handled as a non-public zero-day exploit for at least 94 days. During that time the estimated underground price was around $0-$5k. The vulnerability scanner Nessus provides a plugin with the ID 118745 (RHEL 7 : openvswitch (RHSA-2018:3500)), which helps to determine the existence of the flaw in a target environment. It is assigned to the family Red Hat Local Security Checks and running in the context l. The commercial vulnerability scanner Qualys is able to test this issue with plugin 171775 (SUSE Enterprise Linux Security Update for openvswitch (SUSE-SU-2018:4128-1)).

Upgrading eliminates this vulnerability. A possible mitigation has been published 2 months after the disclosure of the vulnerability.

The vulnerability is also documented in the vulnerability database at Tenable (118745). Similar entries are available at VDB-124264 and VDB-124266.

Productinfo

Name

• Open vSwitch

Version

• 2.7.0
• 2.7.1
• 2.7.2
• 2.7.3
• 2.7.4
• 2.7.5
• 2.7.6

License

• open-source

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