CVE-2020-11091

Published Jun 3, 2020

Last updated 4 years ago

CVSS medium 5.8

Overview

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.
Source: security-advisories@github.com
NVD status: Analyzed

Risk scores

CVSS 3.1

Type: Primary
Base score: 5.8
Impact score: 4
Exploitability score: 1.3
Vector string: CVSS:3.1/AV:N/AC:H/PR:H/UI:N/S:C/C:N/I:H/A:N
Severity: MEDIUM

CVSS 2.0

Type: Primary
Base score: 3.5
Impact score: 2.9
Exploitability score: 6.8
Vector string: AV:N/AC:M/Au:S/C:N/I:P/A:N

Weaknesses

security-advisories@github.com: CWE-350

Hype score: Not currently trending

Configurations

[
  {
    "nodes": [
      {
        "negate": false,
        "cpeMatch": [
          {
            "criteria": "cpe:2.3:a:weave:weave_net:*:*:*:*:*:*:*:*",
            "vulnerable": true,
            "matchCriteriaId": "7C177AA9-82EE-41B6-82E8-B83E18077046",
            "versionEndExcluding": "2.6.3"
          }
        ],
        "operator": "OR"
      }
    ]
  }
]

Overview

Risk scores

CVSS 3.1

CVSS 2.0

Weaknesses

Social media

Configurations

References