CVE-2020-8616: A malicious actor who intentionally exploits this lack of effective limitation on the number of fetches perfor

This week

HIGH 8.6REMOTEWATCHLISTUPGRADEMITIGATE

CVE-2020-8616 is a high-severity flaw (CVSS 8.6) affecting bind, debian linux. Below: why it ranks where it does, which versions are affected, what to do, and the exact commands.

A malicious actor who intentionally exploits this lack of effective limitation on the number of fetches performed when processing referrals can, through the use of specially crafted referrals, cause a recursing server to issue a very large number of fetches in an attempt to process the referral. This has at least two potential effects: The performance of the recursing server can potentially be degraded by the additional work required to perform t

Why this priority

High severity
EPSS top 4%: very likely to be exploited
Public exploit reference
Remotely exploitable, no login, no user action
On your watchlist

A fixed release or distro patch exists.

Risk facts

CVSS score	8.6 (High)
Attack vector	Network (remote)
Attack complexity	Low
Privileges needed	None
User interaction	None
EPSS exploit chance	10.9% (top 4%)
CISA exploited list	No
Weakness	CWE-400
Published	2020-05-19
Last modified	2026-06-17

Publisher (CNA): Internet Systems Consortium (ISC) · Vendor: debian · isc

Last updated 2026-06-17 · Sources: CVE Program, NVD, CISA KEV, EPSS and vendor advisories · How we score

Am I affected?

Timeline

2020-05-19 14:15 UTCPublished CVE record published
2026-06-17 03:26 UTCUpdated Record last modified

isc bind UPGRADE

Affected: >= 9.0.0 and <= 9.11.18 · >= 9.12.0 and <= 9.12.4 · >= 9.13.0 and <= 9.13.7 · >= 9.14.0 and <= 9.14.11 · >= 9.15.0 and <= 9.15.6 · >= 9.16.0 and <= 9.16.2 · >= 9.17.0 and <= 9.17.1 · 9.12.4 p1

Fixed in: newer than 9.17.1

Safe to downgrade to: a release before 9.0.0

1. Check installed version

apt-cache policy bind || rpm -q bind || bind --version

2. UPGRADE to newer than 9.17.1 (Debian / Ubuntu)

sudo apt update && sudo apt install --only-upgrade bind

2. UPGRADE (RHEL / Amazon Linux / Fedora)

sudo dnf upgrade bind

Note

Distros often backport fixes without changing the version number. Confirm with the distro advisory or changelog.

3. If no update is available yet, DOWNGRADE to a release before 9.0.0 (Debian / Ubuntu)

apt-cache madison bind sudo apt install bind=<VERSION_BEFORE_9.0.0> sudo apt-mark hold bind

3. If no update is available yet, DOWNGRADE (RHEL / Amazon Linux / Fedora)

dnf --showduplicates list bind sudo dnf downgrade bind-<VERSION_BEFORE_9.0.0> sudo dnf versionlock add bind

Downgrade risk

Downgrading can break dependent software and may reopen older bugs. Read the distro advisory first and test on a non-production host.

After downgrade

Restart the service, and keep the package held until a fixed release ships.

debian debian linux MITIGATE

Affected: 9.0 · 10.0

Fixed in: no fixed release known

Safe to downgrade to: a release before 9.0

Check your OS release

cat /etc/os-release; uname -r

Debian / Ubuntu

sudo apt update && sudo apt full-upgrade

RHEL / Amazon Linux / Fedora

sudo dnf upgrade --refresh

Windows

Install the latest cumulative update from Windows Update

If no patch exists yet

OS downgrades are not safe. Apply the vendor mitigation from the advisory and restrict exposure.

Exact fixes by distribution

A distro patch exists: prefer upgrading over downgrading.

Fedora 46 · root · FIXED · 6.40.04-7.fc46 · FEDORA-2026-7329868400 · source

sudo dnf upgrade --advisory=FEDORA-2026-7329868400

Ubuntu 20.04 · bind9 · FIXED · 1:9.16.1-0ubuntu2.1

sudo apt update && sudo apt install --only-upgrade bind9 dpkg --compare-versions "$(dpkg-query -W -f='${Version}' bind9)" ge "1:9.16.1-0ubuntu2.1" && echo PATCHED || echo STILL-VULNERABLE

Debian 12 · bind9 · FIXED · 1:9.16.3-1

sudo apt update && sudo apt install --only-upgrade bind9 dpkg --compare-versions "$(dpkg-query -W -f='${Version}' bind9)" ge "1:9.16.3-1" && echo PATCHED || echo STILL-VULNERABLE

Debian 13 · bind9 · FIXED · 1:9.16.3-1

sudo apt update && sudo apt install --only-upgrade bind9 dpkg --compare-versions "$(dpkg-query -W -f='${Version}' bind9)" ge "1:9.16.3-1" && echo PATCHED || echo STILL-VULNERABLE

RHEL 6 · bind · FIXED · bind-9.8.2-0.68.rc1.el6_10.7

sudo dnf upgrade --advisory=RHSA-2020:2383 rpm -q bind

RHEL 6.5 Advanced Update Support · bind · FIXED · bind-9.8.2-0.23.rc1.el6_5.9

sudo dnf upgrade --advisory=RHSA-2020:3379 rpm -q bind

RHEL 6.6 Advanced Update Support · bind · FIXED · bind-9.8.2-0.30.rc1.el6_6.11

sudo dnf upgrade --advisory=RHSA-2020:3378 rpm -q bind

RHEL 7 · bind · FIXED · bind-9.11.4-16.P2.el7_8.6

sudo dnf upgrade --advisory=RHSA-2020:2344 rpm -q bind

RHEL 7.2 Advanced Update Support · bind · FIXED · bind-9.9.4-29.el7_2.9

sudo dnf upgrade --advisory=RHSA-2020:3471 rpm -q bind

Alpine 3.20 · bind · FIXED · bind-9.14.12-r0

apk add --upgrade bind apk info -v bind

Alpine 3.21 · bind · FIXED · bind-9.14.12-r0

apk add --upgrade bind apk info -v bind

Alpine 3.22 · bind · FIXED · bind-9.14.12-r0

apk add --upgrade bind apk info -v bind

Alpine 3.23 · bind · FIXED · bind-9.14.12-r0

apk add --upgrade bind apk info -v bind

Amazon Linux 2 · see advisory · FIXED · ALAS2-2020-1426 · source

sudo yum update --advisory=ALAS2-2020-1426

Amazon Linux 1 · see advisory · FIXED · ALAS-2020-1369 · source

sudo yum update --advisory=ALAS-2020-1369

Verify at the official source NVD · CVE Program · Report a problem with this page
Scores and fixes here are computed automatically from those and other public sources. Confirm with the vendor advisory before changing production systems.

Quick answers

How do I fix CVE-2020-8616?

bind: upgrade to newer than 9.17.1; debian linux: mitigate or apply the listed mitigation. Exact commands for each OS are on this page.

Is CVE-2020-8616 being exploited?

CVE-2020-8616 is not on the CISA Known Exploited Vulnerabilities list at the time of the last update. Check again, as this can change.

What does CVE-2020-8616 affect?

CVE-2020-8616 affects bind, debian linux. Severity is high (CVSS 8.6). A malicious actor who intentionally exploits this lack of effective limitation on the number of fetches performed when processing referrals can, through the use of specially crafted referrals, cause a recursing server to issue a very large

How urgent is CVE-2020-8616?

Priority 69/100. High severity; EPSS top 4%: very likely to be exploited; Public exploit reference; Remotely exploitable, no login, no user action; On your watchlist

Software pages

Debian vulnerabilities · BIND DNS vulnerabilities

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References

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