Skip to content
Log inStart free trial

GHSA-33pg-m6jh-5237 CVE-2023-28841 GO-2023-1700

Docker Swarm encrypted overlay network traffic may be unencrypted

Medium Go
Severity
6.8 / 10
Medium · CVSS 3.1
Exploit chance (EPSS)
0.69%
Chance of exploitation in the next 30 days. Higher than 52.83% of scored vulnerabilities.
Known exploited
No
Not in CISA's catalog
Weakness
CWE-311 Missing Encryption of Sensitive Data
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.

An iptables rule designates outgoing VXLAN datagrams with a VNI that corresponds to an encrypted overlay network for IPsec encapsulation.

On Red Hat Enterprise Linux and derivatives such as CentOS and Rocky, the xt_u32 module has been:

This rule is not created when xt_u32 is unavailable, even though the container is still attached to the network.

Impact

Encrypted overlay networks on affected platforms silently transmit unencrypted data. As a result, overlay networks may appear to be functional, passing traffic as expected, but without any of the expected confidentiality or data integrity guarantees.

It is possible for an attacker sitting in a trusted position on the network to read all of the application traffic that is moving across the overlay network, resulting in unexpected secrets or user data disclosure. Thus, because many database protocols, internal APIs, etc. are not protected by a second layer of encryption, a user may rely on Swarm encrypted overlay networks to provide confidentiality, which due to this vulnerability is no longer guaranteed.

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

  • Close the VXLAN port (by default, UDP port 4789) to outgoing traffic at the Internet boundary (see GHSA-vwm3-crmr-xfxw) in order to prevent unintentionally leaking unencrypted traffic over the Internet.
  • Ensure that the xt_u32 kernel module is available on all nodes of the Swarm cluster.

Background

  • #43382 partially discussed this concern, but did not consider the security implications.
  • Mirantis FIELD-5788 essentially duplicates #43382, and was created six months earlier; it similarly overlooked the security implications.
  • #45118 is the ancestor of the final patches, and was where the security implications were discovered.

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:H/I:N/A:N

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

Weakness

CWE-311: Missing Encryption of Sensitive Data

The product does not encrypt sensitive or critical information before storage or transmission.

How to prevent it
  • Requirements: Clearly specify which data or resources are valuable enough that they should be protected by encryption. Require that any transmission or storage of this data/resource should use well-vetted encryption algorithms.
  • Architecture and Design: Ensure that encryption is properly integrated into the system design, including but not necessarily limited to: Encryption that is needed to store or transmit private data of the users of the system Encryption that is needed to protect the system itself from unauthorized disclosure or tampering Identify the separate needs and contexts for encryption: One-way (i.e., only the user or recipient needs to have the key). This can be achieved using public key cryptography, or other techniques in which the encrypting party (i.e., the product) does not need to have access to a private key. Two-way (i.e., the encryption can be automatically performed on behalf of a user, but the key must be available so that the plaintext can be automatically recoverable by that user). This requires storage of the private key in a format that is recoverable only by the user (or perhaps by the operating system) in a way that cannot be recovered by others. Using threat modeling or other techniques, assume that data can be compromised through a separate vulnerability or weakness, and determine where encryption will be most effective. Ensure that data that should be private is not being inadvertently exposed using weaknesses such as insecure permissions (CWE-732). [REF-7]
  • Architecture and Design: When there is a need to store or transmit sensitive data, use strong, up-to-date cryptographic algorithms to encrypt that data. Select a well-vetted algorithm that is currently considered to be strong by experts in the field, and use well-tested implementations. As with all cryptographic mechanisms, the source code should be available for analysis. For example, US government systems require FIPS 140-2 certification. Do not develop custom or private cryptographic algorithms. They will likely be exposed to attacks that are well-understood by cryptographers. Reverse engineering techniques are mature. If the algorithm can be compromised if attackers find out how it works, then it is especially weak. Periodically ensure that the cryptography has not become obsolete. Some older algorithms, once thought to require a billion years of computing time, can now be broken in days or hours. This includes MD4, MD5, SHA1, DES, and other algorithms that were once regarded as strong. [REF-267]
  • Architecture and Design: Compartmentalize the system to have "safe" areas where trust boundaries can be unambiguously drawn. Do not allow sensitive data to go outside of the trust boundary and always be careful when interfacing with a compartment outside of the safe area. Ensure that appropriate compartmentalization is built into the system design, and the compartmentalization allows for and reinforces privilege separation functionality. Architects and designers should rely on the principle of least privilege to decide the appropriate time to use privileges and the time to drop privileges.
  • Implementation, Architecture and Design: When using industry-approved techniques, use them correctly. Don't cut corners by skipping resource-intensive steps (CWE-325). These steps are often essential for preventing common attacks.
  • Implementation: Use naming conventions and strong types to make it easier to spot when sensitive data is being used. When creating structures, objects, or other complex entities, separate the sensitive and non-sensitive data as much as possible.

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-6wrf-mxfj-pf5p
Docker Swarm encrypted overlay network with a single endpoint is unauthenticated
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
Is this in your code?

MergeHarbor checks every repository's dependencies against this database, ranks what matters by exploitability and reachability, routes it to the owning team and opens the fix pull request.

Check your repos with MergeHarbor