CVE-2020-11091 Weave Net clusters susceptible to MitM attacks via IPv6 rogue router advertisements
An attacker with root in a container can send rogue IPv6 router advertisements to intercept host traffic, enabling man-in-the-middle attacks and potential host compromise.
- Exploited in the wild
- Not known
- Login needed
- An administrator
- Attackable
- Over the internet
- Victim action needed
- Not needed
- Fix
- Available
What is CVE-2020-11091?
CVE-2020-11091 is a medium-severity vulnerability in weaveworks Weave, published on 3 Jun 2020. An attacker needs administrator access to exploit it, with no action from the victim.
Official 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.
Weakness: CWE-350
Which versions are affected by CVE-2020-11091?
3 open source packages ship an affected version, including github.com/weaveworks/weave. It affects 1 product.
| Package | Affected | Fixed in |
|---|---|---|
github.com/weaveworks/weave Go | All versions | 2.6.3 |
github.com/weaveworks/weave Go | All versions | 2.6.3 |
github.com/weaveworks/weave Go | All versions | 2.6.3+incompatible |
Products include Weave Weave Net.
How do I fix CVE-2020-11091?
Upgrade github.com/weaveworks/weave to a fixed version for your release line: 2.6.3 or 2.6.3+incompatible.
Is CVE-2020-11091 being exploited?
There is no known exploitation of CVE-2020-11091 in the wild and no public exploit code.
Sources
Also known as GHSA-59qg-grp7-5r73, GO-2022-0794.