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What is CVE-2020-29569?A high-severity flaw in Xen, explained.

High severity7 affected products
The short answer

CVE-2020-29569 is a high-severity flaw (CVSS 8.8) in Xen, published on 15 December 2020. 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 0.4%. If you run an affected version, plan in the vendor’s fix.

Check if it affects you →How to fix it

Published 15 December 2020. Record last updated 19 January 2023. We keep this page's data up to date.

What it does

What is CVE-2020-29569? In plain terms.

An attacker has to be already on the device with an ordinary user account, and nobody has to click anything. If it works, the attacker can read data, change data and take it offline.

The official description

An issue was discovered in the Linux kernel through 5.10.1, as used with Xen through 4.14.x. The Linux kernel PV block backend expects the kernel thread handler to reset ring->xenblkd to NULL when stopped. However, the handler may not have time to run if the frontend quickly toggles between the states connect and disconnect. As a consequence, the block backend may re-use a pointer after it was freed. A misbehaving guest can trigger a dom0 crash by continuously connecting / disconnecting a block frontend. Privilege escalation and information leaks cannot be ruled out. This only affects systems with a Linux blkback.

What kind of flaw is it?

  • CWE-416Use After Free
CVSS 3.1 scoreHigh · 8.8

How an attack on it works

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

  • Where an attacker can beAlready on the device
  • How hard it is to pull offEasy: no special conditions
  • Login needed firstAn ordinary user account
  • Does someone have to clickNo, nobody has to do anything
  • What an attacker getsCan read data, change data and take it offline

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

Exploitation

Is CVE-2020-29569 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 0.4%. 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 days0.4%Its EPSS score, from the latest forecast

Timeline

  1. Published
  2. Record last updated
How Precursor Intelligence ranks it
47out of 100Medium

CVE-2020-29569 scores 47. 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-2020-29569 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-2020-29569? 7 products.

The published record lists 7 products from 4 vendors. Versions are shown as published: "4.1.44 to before 4.2" means from 4.1.44 up to, but not including, 4.2. If you run one of these, check your version, then go to the fix below.

  • Operating system

    Xen

    by Xen

    Affected versions
    up to 4.14.1
  • Operating system

    Linux kernel

    by Linux

    Affected versions
    4.1.44 to before 4.24.4.80 to before 4.4.2544.9.36 to before 4.9.2494.11.9 to before 4.124.12 to before 4.14.2134.15 to before 4.19.164
  • Operating system

    Debian Linux

    by Debian

    Affected versions
    9.010.0
  • Hardware

    Hci Compute Node

    by Netapp

    Affected versions
    version not specified
  • Operating system

    Hci Compute Node BIOS

    by Netapp

    Affected versions
    version not specified
  • Application

    Solidfire & Hci Management Node

    by Netapp

    Affected versions
    version not specified
  • Application

    Solidfire & Hci Storage Node

    by Netapp

    Affected versions
    version not specified
Remediation

How do I fix CVE-2020-29569? 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 advisory 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

6 links
Precursor Intelligence

Does CVE-2020-29569 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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Common questions, answered plainly.

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CVE-2020-29569 is a high-severity flaw in Xen, published on 15 December 2020. An attacker has to be already on the device with an ordinary user account, and nobody has to click anything. If it works, the attacker can read data, change data and take it offline.

It scores 8.8 out of 10 on the CVSS severity scale, which is high. Our risk score for CVE-2020-29569 is 47 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 0.4%. That can change at any time, which is why we keep watching.

For Xen: up to 4.14.1. The record lists 7 products in all, each with its versions, under "Who is affected" on this page.

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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