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CVE-2020-11091

CVE information

Published

2 years ago

Last Modified

2 years ago

CVSSv2.0 Severity

Low

CVSSv3.1 Severity

Medium

Impact Analysis

Description

In Weave Net before version 2.6.3, an attacker able to run a process as root in a container is able to respond to DNS requests from the host and thereby insert themselves as a fake service. In a cluster with an IPv4 internal network, if IPv6 is not totally disabled on the host (via ipv6.disable=1 on the kernel cmdline), it will be either unconfigured or configured on some interfaces, but it's pretty likely that ipv6 forwarding is disabled, ie /proc/sys/net/ipv6/conf//forwarding == 0. Also by default, /proc/sys/net/ipv6/conf//accept_ra == 1. The combination of these 2 sysctls means that the host accepts router advertisements and configure the IPv6 stack using them. By sending rogue router advertisements, an attacker can reconfigure the host to redirect part or all of the IPv6 traffic of the host to the attacker controlled container. Even if there was no IPv6 traffic before, if the DNS returns A (IPv4) and AAAA (IPv6) records, many HTTP libraries will try to connect via IPv6 first then fallback to IPv4, giving an opportunity to the attacker to respond. If by chance you also have on the host a vulnerability like last year's RCE in apt (CVE-2019-3462), you can now escalate to the host. Weave Net version 2.6.3 disables the accept_ra option on the veth devices that it creates..

CVSSv2.0 Score

Severity
Low
Base Score
3.5/10
Exploit Score
6.8/10
Access Vector
Network
Access Complexity
Medium
Authentication Required
Single
Impact Score
2.9/10
Confidentiality Impact
None
Availability Impact
None
Integrity Impact
Partial

CVSSv3.1 Score

Severity
Medium
Base Score
5.8/10
Exploit Score
1.3/10
Access Vector
Network
Access Complexity
High
Privileges Required
High
Impact Score
4/10
Confidentiality Impact
None
Availability Impact
None
Integrity Impact
High
Scope
Changed
User Interaction
None

Products Affected

CPE Affected Vulnerable Excluding Edit
cpe:2.3:a:weave:weave_net:*:*:*:*:*:*:*:*
  Yes
- 2.6.3