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GHSA-6wrf-mxfj-pf5p CVE-2023-28842 GO-2023-1701

Docker Swarm encrypted overlay network with a single endpoint is unauthenticated

Medium Go
Severity
6.8 / 10
Medium · CVSS 3.1
Exploit chance (EPSS)
1.44%
Chance of exploitation in the next 30 days. Higher than 73.19% of scored vulnerabilities.
Known exploited
No
Not in CISA's catalog
Weakness
CWE-420 Unprotected Alternate Channel
CWE-636 Not Failing Securely ('Failing Open')
Fix
20.10.24
Upgrade github.com/docker/docker to this version or later

Description

Moby is an open source container framework developed by Docker Inc. that is distributed as Docker, Mirantis Container Runtime, and various other downstream projects/products. The Moby daemon component (dockerd), which is developed as moby/moby is commonly referred to as Docker.

Swarm Mode, which is compiled in and delivered by default in dockerd and is thus present in most major Moby downstreams, is a simple, built-in container orchestrator that is implemented through a combination of SwarmKit and supporting network code.

The overlay network driver is a core feature of Swarm Mode, providing isolated virtual LANs that allow communication between containers and services across the cluster. This driver is an implementation/user of VXLAN, which encapsulates link-layer (Ethernet) frames in UDP datagrams that tag the frame with a VXLAN Network ID (VNI) that identifies the originating overlay network. In addition, the overlay network driver supports an optional, off-by-default encrypted mode, which is especially useful when VXLAN packets traverses an untrusted network between nodes.

Encrypted overlay networks function by encapsulating the VXLAN datagrams through the use of the IPsec Encapsulating Security Payload protocol in Transport mode. By deploying IPSec encapsulation, encrypted overlay networks gain the additional properties of source authentication through cryptographic proof, data integrity through check-summing, and confidentiality through encryption.

When setting an endpoint up on an encrypted overlay network, Moby installs three iptables (Linux kernel firewall) rules that enforce both incoming and outgoing IPSec. These rules rely on the u32 iptables extension provided by the xt_u32 kernel module to directly filter on a VXLAN packet's VNI field, so that IPSec guarantees can be enforced on encrypted overlay networks without interfering with other overlay networks or other users of VXLAN.

The overlay driver dynamically and lazily defines the kernel configuration for the VXLAN network on each node as containers are attached and detached. Routes and encryption parameters are only defined for destination nodes that participate in the network. The iptables rules that prevent encrypted overlay networks from accepting unencrypted packets are not created until a peer is available with which to communicate.

Impact

Encrypted overlay networks silently accept cleartext VXLAN datagrams that are tagged with the VNI of an encrypted overlay network. As a result, it is possible to inject arbitrary Ethernet frames into the encrypted overlay network by encapsulating them in VXLAN datagrams. The implications of this can be quite dire, and GHSA-vwm3-crmr-xfxw should be referenced for a deeper exploration.

Patches

Patches are available in Moby releases 23.0.3, and 20.10.24. As Mirantis Container Runtime's 20.10 releases are numbered differently, users of that platform should update to 20.10.16.

Workarounds

  • In multi-node clusters, deploy a global ‘pause’ container for each encrypted overlay network, on every node. For example, use the registry.k8s.io/pause image and a --mode global service.
  • For a single-node cluster, do not use overlay networks of any sort. Bridge networks provide the same connectivity on a single node and have no multi-node features. The Swarm ingress feature is implemented using an overlay network, but can be disabled by publishing ports in host mode instead of ingress mode (allowing the use of an external load balancer), and removing the ingress network.
  • If encrypted overlay networks are in exclusive use, block UDP port 4789 from traffic that has not been validated by IPSec. For example, iptables -A INPUT -m udp —-dport 4789 -m policy --dir in --pol none -j DROP.

Background

Related

Affected versions

Go

PackageVulnerableFixed in
github.com/docker/docker
>= 1.12.0, < 20.10.24
20.10.24
github.com/docker/docker
>= 23.0.0, < 23.0.3
23.0.3
github.com/docker/docker
>= 1.12.0, < 20.10.24+incompatible
>= 23.0.0+incompatible, < 23.0.3+incompatible
20.10.24+incompatible
23.0.3+incompatible

How to fix

Move to the fixed version or later with your package manager, update the lockfile, and run your tests. If the package only arrives through another dependency, upgrade that dependency first. If none of its releases pulls a fixed version yet, force the version with your package manager's override.

github.com/docker/docker Go → 20.10.24

go
go get github.com/docker/docker@v20.10.24 && go mod tidy

Severity breakdown

CVSS 3.1 6.8

CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:C/C:N/I:H/A:N

Attack vector
Network
Attack complexity
High
Privileges required
None
User interaction
None
Scope
Changed
Confidentiality
None
Integrity
High
Availability
None

Weakness

CWE-420: Unprotected Alternate Channel

The product protects a primary channel, but it does not use the same level of protection for an alternate channel.

How to prevent it
  • Architecture and Design: Identify all alternate channels and use the same protection mechanisms that are used for the primary channels.

CWE-636: Not Failing Securely ('Failing Open')

When the product encounters an error condition or failure, its design requires it to fall back to a state that is less secure than other options that are available, such as selecting the weakest encryption algorithm or using the most permissive access control restrictions.

How to prevent it
  • Architecture and Design: Subdivide and allocate resources and components so that a failure in one part does not affect the entire product.

References

Advisories

Packages

Other links

Timeline

  1. Published
  2. Last updated by the source
  3. Latest EPSS score
AdvisorySeverityWhy it's related
GHSA-232p-vwff-86mp
Docker Swarm encrypted overlay network may be unauthenticated
High Linked by the source
GHSA-33pg-m6jh-5237
Docker Swarm encrypted overlay network traffic may be unencrypted
Medium Linked by the source
GHSA-rg2x-37c3-w2rh
Docker: Race condition in docker cp allows bind mount redirection to host path
High Also affects github.com/docker/docker
GHSA-vp62-88p7-qqf5
Docker: Race condition in docker cp allows creation of arbitrary empty files on the host via symlink swap
Medium Also affects github.com/docker/docker
GHSA-x86f-5xw2-fm2r
Docker: `PUT /containers/{id}/archive` executes container binary on the host
High Also affects github.com/docker/docker
GO-2026-4887
Moby has AuthZ plugin bypass when provided oversized request bodies
High Also affects github.com/docker/docker
GHSA-pxq6-2prw-chj9
Moby has an Off-by-one error in its plugin privilege validation
High Also affects github.com/docker/docker
GHSA-4vq8-7jfc-9cvp
Moby firewalld reload removes bridge network isolation
Medium Also affects github.com/docker/docker
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