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What is CVE-2023-28841?A medium-severity flaw in Moby, explained.

Medium severity1 affected product
The short answer

CVE-2023-28841 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 0.7%. If you run an affected version, plan in the vendor’s fix.

Check if it affects you →How to fix it

Published 4 April 2023. Record last updated 15 September 2023. We keep this page's data up to date.

What it does

What is CVE-2023-28841? 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 read 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.

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

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 use Swarm encrypted overlay networks to provide confidentiality, which due to this vulnerability this is no longer guaranteed.

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. Close the VXLAN port (by default, UDP port 4789) to outgoing traffic at the Internet boundary in order to prevent unintentionally leaking unencrypted traffic over the Internet, and/or ensure that the `xt_u32` kernel module is available on all nodes of the Swarm cluster.

What kind of flaw is it?

  • CWE-311Missing Encryption of Sensitive Data
  • CWE-636Not Failing Securely ('Failing Open')
  • CWE-755Improper Handling of Exceptional Conditions
CVSS 3.1 scoreMedium · 6.8

How an attack on it works

Read straight from its severity rating, translated out of the shorthand.

  • Where an attacker can beAnywhere on the internet
  • How hard it is to pull offHard: conditions must line up
  • Login needed firstNo login needed
  • Does someone have to clickNo, nobody has to do anything
  • What an attacker getsCan read data

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

Exploitation

Is CVE-2023-28841 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 0.7%. That can change at any time, which is why we keep watching.

Known to be exploitedNoNot on the list of exploited flaws today
Chance of use in the next 30 days0.7%Its EPSS score, from the latest forecast

Timeline

  1. Published
  2. Record last updated
How Precursor Intelligence ranks it
51out of 100Medium

CVE-2023-28841 scores 51. Action: Plan remediation.

We keep the score of every published flaw up to date as the evidence changes. Four things go into the score, and evidence that criminals are actually using it counts most. In order:

  • Evidence it is being exploitedBiggest factor
  • How severe it isStrong factor
  • How widely exposed it isSmaller factor
  • Threat activity around itSmaller factor

85 and above is Critical. Anything confirmed as exploited is always marked for an emergency patch, whatever its score.

When CVE-2023-28841 matches software you track, it lands in your list with its score and the reasons behind it.

See your own ranked list →
Affected products

Who is affected by CVE-2023-28841? One product.

The published record lists 1 product from 1 vendor. Versions are shown as published: "1.12.0 to before 20.10.24" means from 1.12.0 up to, but not including, 20.10.24. If you run one of these, check your version, then go to the fix below.

  • Application

    Moby

    by Mobyproject

    Affected versions
    1.12.0 to before 20.10.2423.0.0 to before 23.0.3
Remediation

How do I fix CVE-2023-28841? Four steps.

  1. Check whether you run itCompare 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 fixInstall 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 todayFollow 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 itTrack 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

11 links
Precursor Intelligence

Does CVE-2023-28841 affect you? We'll keep checking.

Looking flaws up one at a time doesn't scale. Tell us what you run once, and we tell you which flaws matter to you, in what order, and keep watching for new ones.

  1. Tell us what you runPick your software from a list, or let us work it out from your website.
  2. We match it to every flawOver 400,000 published flaws, checked against your list.
  3. Ranked by real-world riskA 0 to 100 score, led by evidence criminals are using it.
  4. Told as soon as we knowAn alert by email, in the app or by webhook to your own tools.
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FAQ

Common questions, answered plainly.

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CVE-2023-28841 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 read data.

It scores 6.8 out of 10 on the CVSS severity scale, which is medium. Our risk score for CVE-2023-28841 is 51 out of 100, which is Medium. Its action is "Plan remediation". No sign of exploitation and a low forecast. Patch it in your normal update cycle.

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 0.7%. That can change at any time, which is why we keep watching.

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

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.

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