CVE-2023-28842
Official description Straight from the sourceThe vendor's or NVD's own wording, published unedited. Authoritative, but often terse — it says what broke, rarely what to do.
NVD · uneditedMoby) 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 the VXLAN metadata, including 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. 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 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. Some workarounds are available. In multi-node clusters, deploy a global ‘pause’ container for each encrypted overlay network, on every node. 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.
Technical summary Written by usOur analysis, written from the advisory, the CVSS vector and the affected-version data. It adds context the advisory leaves out, and never invents facts that are not in the source.
dbcve analysis · high confidenceIn Moby's overlay network driver, the iptables rules that prevent encrypted overlay networks from accepting unencrypted VXLAN traffic are only created when a peer is available to communicate with. This creates a window where encrypted overlay networks silently accept cleartext VXLAN datagrams tagged with the encrypted network's VNI, allowing injection of arbitrary Ethernet frames and bypassing the expected IPSec protections.
Verify against the referenced sources before acting — the references below are authoritative for this CVE, this summary is not.
Affected products & versions What the vendor confirmedThe version ranges the vendor confirmed as vulnerable. If your version sits inside a range here, treat yourself as exposed until you have upgraded.
NVD · CPE data>= 1.12.0, < 20.10.24>= 23.0.0, < 23.0.3CVSS breakdown How the score is builtThe industry scoring standard. It rates how the flaw is reached, what it takes to exploit, and what an attacker gains — the score is derived from those, not the other way round.
From the vector- Attack vector
- Network
- Complexity
- High
- Privileges
- None
- User interaction
- None
- Scope
- Changed
- Confidentiality
- None
- Integrity
- High
- Availability
- None
CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:C/C:N/I:H/A:N
Am I affected? How to checkSteps we derive from the advisory and the affected-version data, so you can decide whether this CVE reaches your setup. They are a guide, not a scan — your own configuration is the authority.
dbcve checksWork through these to decide whether this CVE applies to you.
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Check the installed Moby or Docker Engine versionRun `docker version --format '{{.Server.Version}}'` or check the package manager for moby/docker versionAffected if The version is >= 1.12.0 and < 20.10.24, OR >= 23.0.0 and < 23.0.3
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Identify encrypted overlay networksRun `docker network ls --filter type=overlay` and for each overlay network, inspect it with `docker network inspect <network-name>` to check if `encrypted` is true in the optionsAffected if There exists an overlay network with the `encrypted` option set to true
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Verify peer nodes exist on the encrypted overlay networkRun `docker network inspect <encrypted-network>` and check the `Peers` array in the endpoint information; or run `docker node ls` to confirm multi-node swarm setupAffected if The encrypted overlay network has no peer nodes (empty Peers array) or the environment is a single-node setup without swarm peers
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Inspect iptables rules for the encrypted network VNIRun `sudo iptables -L -n -v | grep -i vxlan` or specifically `sudo iptables -L DOCKER -n --line-numbers` to look for rules matching the encrypted network's VNI; the rule should DROP VXLAN traffic with that VNI from non-encrypted sourcesAffected if No DROP rule exists for the encrypted overlay network's VNI, or rules are missing entirely for that network
You are affected if you run a vulnerable Moby/Docker version (pre-20.10.24 or pre-23.0.3) AND have encrypted overlay networks with no peer nodes, where the protective iptables DROP rules for VXLAN traffic are missing.
Generated from the published advisory. Verify against your own configuration.
Remediation Closing itWhat it takes to close this. Where a vendor fix exists we point at it; where none exists we say so plainly, and can build one. Effort estimates are scoped from the advisory, not from your codebase.
dbcve · scoped20.10.2423.0.3
Update to Moby 23.0.3/20.10.24 or Mirantis Container Runtime 20.10.16 to patch the missing iptables rule installation. As a workaround, ensure each node has a peer by deploying a global pause container before using encrypted overlay networks.
Moby 23.0.3 or later / Moby 20.10.24 or later / Mirantis Container Runtime 20.10.16
- Upgrade Moby to version 23.0.3 or later if using the 23.x release line
- OR upgrade Moby to version 20.10.24 or later if using the 20.10.x release line
- For Mirantis Container Runtime users, upgrade to version 20.10.16
- After upgrading, restart the dockerd daemon to apply the changes
- Verify that encrypted overlay networks are functioning correctly post-upgrade
Generated from the published advisory — verify against the referenced sources before acting.
- Consultation2.0 h
- Implementation4.0 h
- Testing3.0 h
- Review / QA1.0 h
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References Go to the primary sourcePrimary sources — vendor advisories, patches and trackers. Where our summary and a reference disagree, the reference wins.
Primary sourcesPractitioner notes
ContributedPeer-ranked notes from engineers who’ve handled CVE-2023-28842 in production — separate from our analysis above.
The advisory tells you what broke. It rarely tells you what actually worked. If you’ve dealt with this one, that detail is what the next engineer is searching for.
- The version that genuinely resolved it — not the one the vendor claimed
- A config change or rule that shut the vector down
- A gotcha in the upgrade path that cost you an afternoon
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