CVE-2020-11091 Details

CVE-2020-11091

Published: 2020-06-03
Last Modified: 2020-06-09
CVE Author: NIST National Vulnerability Database
CVE Assigner: security-advisories@github.com
Summary

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.

Analysis
Common Vulnerability Score System v2.0
Severity Low
Base Score 3.5/10
Exploit Score 6.8/10
Access Vector Network
Access Complexity Medium
Authentication Single
Impact Score 2.9/10
Confidentiality Impact None
Availability Impact None
Integrity Impact Partial
Vector String AV:N/AC:M/Au:S/C:N/I:P/A:N
Common Vulnerability Score System v3.1
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
Vector String CVSS:3.1/AV:N/AC:H/PR:H/UI:N/S:C/C:N/I:H/A:N
Products Reported
CPE Vulnerable Start Excluding
cpe:2.3:a:weave:weave_net:*:*:*:*:*:*:*:* Yes - 2.6.3
References

https://github.com/weaveworks/weave/commit/15f21f1899060f7716c70a8555a084e836f39a60
https://github.com/weaveworks/weave/security/advisories/GHSA-59qg-grp7-5r73

CVE ID
CVE-2020-11091
Published
2020-06-03
Modified
2020-06-09
CVSSv2.0
Low
CVSSv3.1
Medium
PCI Compliance
Fail
US-CERT Alert
No
CWE
CWE-350

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