# What is CVE-2023-28842?

> CVE-2023-28842 is a medium-severity flaw (CVSS 6.8) in Moby from Mobyproject, published on 4 April 2023. It is not on the list of flaws known to be exploited today. The latest forecast puts its chance of use in the next 30 days at 1.4%. If you run an affected version, plan in the vendor’s fix.

Canonical page: https://www.precursorintelligence.com/what-is/cve-2023-28842

## At a glance

- **Verdict:** Plan it in. No sign of exploitation and a low forecast. Patch it in your normal update cycle.
- **Precursor Intelligence risk score:** 30 out of 100 (Low); action: Monitor. Kept up to date as the evidence changes.
- **Severity:** Medium (CVSS 6.8 out of 10)
- **Known to be exploited:** No, not on the list of flaws known to be exploited today
- **Chance of use in the next 30 days:** 1.4% (latest exploit-likelihood forecast)
- **Published:** 4 April 2023
- **Record last updated:** 15 September 2023
- **Main product:** Moby from Mobyproject
- **Affected products:** 1

## What is CVE-2023-28842? In plain terms

It can be attacked from anywhere on the internet without logging in, and nobody has to click anything. If it works, the attacker can change data.

### The official 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 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.

### What kind of flaw is it?

- CWE-755: Improper Handling of Exceptional Conditions
- CWE-420: Unprotected Alternate Channel
- CWE-636: Not Failing Securely ('Failing Open')

### How an attack on it works

- Where an attacker can be: Anywhere on the internet
- How hard it is to pull off: Hard: conditions must line up
- Login needed first: No login needed
- Does someone have to click: No, nobody has to do anything
- What an attacker gets: Can change data

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

## Is CVE-2023-28842 being exploited? Not that we know of

It is not on the list of flaws known to be exploited today. The latest forecast puts the chance of it being used in the next 30 days at 1.4%. That can change at any time, which is why we keep watching.

Exploit likelihood over the last 7 days: 1.4%, 1.4%, 1.4%, 1.4%, 1.4%, 1.4%, 1.4%.

### Timeline

- 4 April 2023: Published
- 15 September 2023: Record last updated

### How Precursor Intelligence ranks it

CVE-2023-28842 scores **30 out of 100 (Low)**, with the action "Monitor".

Every published flaw gets a risk score from 0 to 100, kept up to date as the evidence changes. Four things go into the score, from the one that counts most to the ones that count less:

- Evidence it is being exploited: biggest factor
- How severe it is: strong factor
- How widely exposed it is: smaller factor
- Threat activity around it: smaller factor

85 and above is Critical. Anything confirmed as exploited is always marked for an emergency patch, whatever its score. When this flaw matches software you track, it lands in your list with its score and the reasons behind it.

## Who is affected by CVE-2023-28842?

The published record lists 1 product. Versions are as published: "1.12.0 to before 20.10.24" means from 1.12.0 up to, but not including, 20.10.24.

- [Moby](https://www.precursorintelligence.com/product/mobyproject/moby) by [Mobyproject](https://www.precursorintelligence.com/vendors/mobyproject) (Application): 1.12.0 to before 20.10.24, 23.0.0 to before 23.0.3

## How do I fix CVE-2023-28842?

1. **Check whether you run it.** Compare your versions with the affected products above. Not sure what you run? Precursor Intelligence can work it out from your public website, or you can pick it from a list.
2. **Apply the vendor’s fix.** Install the update named in the vendor’s advisory. We’ve put the advisories and patch notes first in the list.
3. **If you can’t patch today.** Follow any mitigation the vendor publishes, and limit who can reach the affected system from the internet until the update is in.
4. **Keep an eye on it.** Track the product and we tell you as soon as we spot this flaw on the list of exploited flaws, or a jump in its exploit likelihood.

### References

- [github.com](https://github.com/moby/libnetwork/security/advisories/GHSA-gvm4-2qqg-m333) (Vendor advisory)
- [github.com](https://github.com/moby/moby/security/advisories/GHSA-6wrf-mxfj-pf5p) (Mitigation, Vendor advisory)
- [github.com](https://github.com/moby/moby/security/advisories/GHSA-vwm3-crmr-xfxw) (Vendor advisory)
- [github.com](https://github.com/moby/moby/security/advisories/GHSA-232p-vwff-86mp) (Not applicable)
- [github.com](https://github.com/moby/moby/security/advisories/GHSA-33pg-m6jh-5237) (Not applicable)
- [lists.fedoraproject.org](https://lists.fedoraproject.org/archives/list/package-announce@lists.fedoraproject.org/message/LYZOKMMVX4SIEHPJW3SJUQGMO5YZCPHC/)
- [lists.fedoraproject.org](https://lists.fedoraproject.org/archives/list/package-announce@lists.fedoraproject.org/message/XNF4OLYZRQE75EB5TW5N42FSXHBXGWFE/)
- [lists.fedoraproject.org](https://lists.fedoraproject.org/archives/list/package-announce@lists.fedoraproject.org/message/ZTE4ITXXPIWZEQ4HYQCB6N6GZIMWXDAI/)

## Questions

### What is CVE-2023-28842?

CVE-2023-28842 is a medium-severity flaw in Moby from Mobyproject, published on 4 April 2023. It can be attacked from anywhere on the internet without logging in, and nobody has to click anything. If it works, the attacker can change data.

### How serious is CVE-2023-28842?

It scores 6.8 out of 10 on the CVSS severity scale, which is medium. Our risk score for CVE-2023-28842 is 30 out of 100, which is Low. Its action is "Monitor". No sign of exploitation and a low forecast. Patch it in your normal update cycle.

### Is CVE-2023-28842 being exploited?

It is not on the list of flaws known to be exploited today. The latest forecast puts the chance of it being used in the next 30 days at 1.4%. That can change at any time, which is why we keep watching.

### Which versions does CVE-2023-28842 affect?

For Moby from Mobyproject: 1.12.0 to before 20.10.24, 23.0.0 to before 23.0.3.

### How do I fix CVE-2023-28842?

Install the update the vendor names in its advisory, linked first under "How do I fix" on this page. If you can't patch today, follow the vendor's mitigation and limit who can reach the affected system from the internet.

## Does CVE-2023-28842 affect you?

Precursor Intelligence keeps checking for you:

- **Tell us what you run.** Pick your software from a list, or let us work it out from your website.
- **We match it to every flaw.** Over 400,000 published flaws, checked against your list.
- **Ranked by real-world risk.** Every flaw gets a 0 to 100 risk score, kept up to date, led by evidence criminals are using it.
- **Told as soon as we know.** An alert by email, in the app or by webhook to your own tools.

Start free (no card, nothing to install): https://www.precursorintelligence.com/register
Book a demo: https://www.precursorintelligence.com/contact