# What is CVE-2020-8617?

> CVE-2020-8617 is a medium-severity flaw (CVSS 5.9) in Bind from Isc, published on 19 May 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 93%. If you run an affected version, plan in the vendor’s fix.

Canonical page: https://www.precursorintelligence.com/what-is/cve-2020-8617

## At a glance

- **Verdict:** Fix this soon. Not confirmed as exploited yet, but serious or likely enough that it should not wait for a quiet month.
- **Precursor Intelligence risk score:** 66 out of 100 (Medium); action: Plan remediation. Kept up to date as the evidence changes.
- **Severity:** Medium (CVSS 5.9 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:** 93% (latest exploit-likelihood forecast)
- **Published:** 19 May 2020
- **Record last updated:** 7 November 2023
- **Main product:** Bind from Isc
- **Affected products:** 5

## What is CVE-2020-8617? 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 take it offline.

### The official description

Using a specially-crafted message, an attacker may potentially cause a BIND server to reach an inconsistent state if the attacker knows (or successfully guesses) the name of a TSIG key used by the server. Since BIND, by default, configures a local session key even on servers whose configuration does not otherwise make use of it, almost all current BIND servers are vulnerable. In releases of BIND dating from March 2018 and after, an assertion check in tsig.c detects this inconsistent state and deliberately exits. Prior to the introduction of the check the server would continue operating in an inconsistent state, with potentially harmful results.

### What kind of flaw is it?

- CWE-617: Reachable Assertion

### 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 take it offline

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

## Is CVE-2020-8617 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 93%. That can change at any time, which is why we keep watching.

Exploit likelihood over the last 7 days: 93%, 93%, 93%, 93%, 93%, 93%, 93%.

### Timeline

- 19 May 2020: Published
- 7 November 2023: Record last updated

### How Precursor Intelligence ranks it

CVE-2020-8617 scores **66 out of 100 (Medium)**, with the action "Plan remediation".

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-2020-8617?

The published record lists 5 products.

- [Bind](https://www.precursorintelligence.com/product/isc/bind) by [Isc](https://www.precursorintelligence.com/vendors/isc) (Application): 9.0.0 to 9.11.18, 9.12.0 to 9.12.4, 9.12.4-p1, 9.12.4-p2, 9.13.0 to 9.13.7, 9.14.0 to 9.14.11, 9.15.0 to 9.15.6, 9.16.0 to 9.16.2, 9.17.0 to 9.17.1
- [Ubuntu Linux](https://www.precursorintelligence.com/product/canonical/ubuntu_linux) by [Canonical](https://www.precursorintelligence.com/vendors/canonical) (Operating system): 12.04, 14.04, 16.04, 18.04, 19.10, 20.04
- [Debian Linux](https://www.precursorintelligence.com/product/debian/debian_linux) by [Debian](https://www.precursorintelligence.com/vendors/debian) (Operating system): 8.0, 9.0, 10.0
- [Fedora](https://www.precursorintelligence.com/product/fedoraproject/fedora) by [Fedoraproject](https://www.precursorintelligence.com/vendors/fedoraproject) (Operating system): 31, 32
- [Leap](https://www.precursorintelligence.com/product/opensuse/leap) by [Opensuse](https://www.precursorintelligence.com/vendors/opensuse) (Operating system): 15.1, 15.2

## How do I fix CVE-2020-8617?

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

- [openwall.com](http://www.openwall.com/lists/oss-security/2020/05/19/4) (Mailing list, Patch, Third-party advisory)
- [kb.isc.org](https://kb.isc.org/docs/cve-2020-8617) (Patch, Vendor advisory)
- [lists.opensuse.org](http://lists.opensuse.org/opensuse-security-announce/2020-10/msg00041.html) (Mailing list, Third-party advisory)
- [lists.opensuse.org](http://lists.opensuse.org/opensuse-security-announce/2020-10/msg00044.html) (Mailing list, Third-party advisory)
- [packetstormsecurity.com](http://packetstormsecurity.com/files/157836/BIND-TSIG-Denial-Of-Service.html) (Third-party advisory, Vulnerability database)
- [lists.debian.org](https://lists.debian.org/debian-lts-announce/2020/05/msg00031.html) (Mailing list, Third-party advisory)
- [lists.fedoraproject.org](https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/JKJXVBOKZ36ER3EUCR7VRB7WGHIIMPNJ/)
- [lists.fedoraproject.org](https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/WOGCJS2XQ3SQNF4W6GLZ73LWZJ6ZZWZI/)
- [security.netapp.com](https://security.netapp.com/advisory/ntap-20200522-0002/) (Third-party advisory)
- [usn.ubuntu.com](https://usn.ubuntu.com/4365-1/) (Third-party advisory)
- [usn.ubuntu.com](https://usn.ubuntu.com/4365-2/) (Third-party advisory)
- [debian.org](https://www.debian.org/security/2020/dsa-4689) (Third-party advisory)

## Questions

### What is CVE-2020-8617?

CVE-2020-8617 is a medium-severity flaw in Bind from Isc, published on 19 May 2020. It can be attacked from anywhere on the internet without logging in, and nobody has to click anything. If it works, the attacker can take it offline.

### How serious is CVE-2020-8617?

It scores 5.9 out of 10 on the CVSS severity scale, which is medium. Our risk score for CVE-2020-8617 is 66 out of 100, which is Medium. Its action is "Plan remediation". Not confirmed as exploited yet, but serious or likely enough that it should not wait for a quiet month.

### Is CVE-2020-8617 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 93%. That can change at any time, which is why we keep watching.

### Which versions does CVE-2020-8617 affect?

For Bind from Isc: 9.0.0 to 9.11.18, 9.12.0 to 9.12.4, 9.12.4-p1, 9.12.4-p2, 9.13.0 to 9.13.7, 9.14.0 to 9.14.11 and 3 more. The record lists 5 products in all, each with its versions, under "Who is affected" on this page.

### How do I fix CVE-2020-8617?

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-2020-8617 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.

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