QID 982384

QID 982384: Go (go) Security Update for github.com/weaveworks/weave (GHSA-59qg-grp7-5r73)

Security update has been released for github.com/weaveworks/weave to fix the vulnerability.

Note: The preceding description block is extracted directly from the security advisory. Using automation, we have attempted to clean and format it as much as possible without introducing additional issues.

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 its 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 years RCE in apt (CVE-2019-3462), you can now escalate to the host.

CVSS V3 rated as Medium - 5.8 severity.

CVSS V2 rated as Medium - 3.5 severity.

Solution

Weave Net version 2.6.3 (to be released soon) will disable the accept_ra option on the veth devices that it creates.Workaround:
Users should not run containers with CAP_NET_RAW capability. This has been the advice from Weave Net for years.
https://www.weave.works/docs/net/latest/kubernetes/kube-addon/#-securing-the-setup

Vendor References

GHSA-59qg-grp7-5r73 - github.com/advisories/GHSA-59qg-grp7-5r73

CVEs related to QID 982384

CVE-2020-11091 |

Software Advisories

Advisory ID	Software	Component	Link
GHSA-59qg-grp7-5r73	github.com/weaveworks/weave		github.com/advisories/GHSA-59qg-grp7-5r73

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