CVE-2023-2911: If the `recursive-clients` quota is reached on a BIND 9 resolver configured with both `stale-answer-enable yes

This month

HIGH 7.5REMOTEWATCHLISTUPGRADEMITIGATEMITIGATE

CVE-2023-2911 is a high-severity flaw (CVSS 7.5) affecting bind, debian linux, fedora. Below: why it ranks where it does, which versions are affected, what to do, and the exact commands.

If the `recursive-clients` quota is reached on a BIND 9 resolver configured with both `stale-answer-enable yes;` and `stale-answer-client-timeout 0;`, a sequence of serve-stale-related lookups could cause `named` to loop and terminate unexpectedly due to a stack overflow. This issue affects BIND 9 versions 9.16.33 through 9.16.41, 9.18.7 through 9.18.15, 9.16.33-S1 through 9.16.41-S1, and 9.18.11-S1 through 9.18.15-S1.

Why this priority

High severity
Remotely exploitable, no login, no user action
On your watchlist

A fixed release or distro patch exists.

Risk facts

CVSS score	7.5 (High)
Attack vector	Network (remote)
Attack complexity	Low
Privileges needed	None
User interaction	None
EPSS exploit chance	2.5% (top 16%)
CISA exploited list	No
Weakness	CWE-787
Published	2023-06-21
Last modified	2026-10-24

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

Last updated 2026-10-24 · Sources: CVE Program, NVD, CISA KEV, EPSS and vendor advisories · How we score

Am I affected?

Timeline

2023-06-21 17:15 UTCPublished CVE record published
2026-10-24 19:10 UTCUpdated Record last modified

isc bind UPGRADE

Affected: >= 9.16.33 and <= 9.16.41 · >= 9.18.7 and <= 9.18.15 · >= 9.18.11 and <= 9.18.15

Fixed in: newer than 9.18.15

Safe to downgrade to: a release before 9.16.33

1. Check installed version

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

2. UPGRADE to newer than 9.18.15 (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 9.16.33 (Debian / Ubuntu)

apt-cache madison bind sudo apt install bind=<VERSION_BEFORE_9.16.33> 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_9.16.33> 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: 11.0 · 12.0

Fixed in: no fixed release known

Safe to downgrade to: a release before 11.0

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.

fedoraproject fedora MITIGATE

Affected: 37 · 38

Fixed in: no fixed release known

Safe to downgrade to: a release before 37

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.

netapp active iq unified manager MITIGATE

Affected: all versions

Fixed in: no fixed release known

Safe to downgrade to: no unaffected older release

1. Check installed version

apt-cache policy active-iq-unified-manager || rpm -q active-iq-unified-manager || active-iq-unified-manager --version

No fixed or unaffected release known

Apply the vendor mitigation from the advisory, disable the affected feature, or restrict network access.

netapp h700s firmware MITIGATE

Affected: all versions

Fixed in: no fixed release known

Safe to downgrade to: no unaffected older release

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.

netapp h300s firmware MITIGATE

Affected: all versions

Fixed in: no fixed release known

Safe to downgrade to: no unaffected older release

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 · conda · FIXED · 26.9.4-2.fc46 · FEDORA-2026-09931756f1 · source

sudo dnf upgrade --advisory=FEDORA-2026-09931756f1

Ubuntu 20.04 · bind9 · FIXED · 1:9.16.1-0ubuntu2.15

sudo apt update && sudo apt install --only-upgrade bind9 dpkg --compare-versions "$(dpkg-query -W -f='${Version}' bind9)" ge "1:9.16.1-0ubuntu2.15" && echo PATCHED || echo STILL-VULNERABLE

Ubuntu 22.04 · bind9 · FIXED · 1:9.18.12-0ubuntu0.22.04.2

sudo apt update && sudo apt install --only-upgrade bind9 dpkg --compare-versions "$(dpkg-query -W -f='${Version}' bind9)" ge "1:9.18.12-0ubuntu0.22.04.2" && echo PATCHED || echo STILL-VULNERABLE

Ubuntu 24.04 · bind9 · FIXED · 1:9.18.12-1ubuntu2

sudo apt update && sudo apt install --only-upgrade bind9 dpkg --compare-versions "$(dpkg-query -W -f='${Version}' bind9)" ge "1:9.18.12-1ubuntu2" && echo PATCHED || echo STILL-VULNERABLE

Ubuntu 24.10 · bind9 · FIXED · 1:9.18.12-1ubuntu2

sudo apt update && sudo apt install --only-upgrade bind9 dpkg --compare-versions "$(dpkg-query -W -f='${Version}' bind9)" ge "1:9.18.12-1ubuntu2" && echo PATCHED || echo STILL-VULNERABLE

Ubuntu 25.04 · bind9 · FIXED · 1:9.18.12-1ubuntu2

sudo apt update && sudo apt install --only-upgrade bind9 dpkg --compare-versions "$(dpkg-query -W -f='${Version}' bind9)" ge "1:9.18.12-1ubuntu2" && echo PATCHED || echo STILL-VULNERABLE

Debian 12 · bind9 · FIXED · 1:9.18.16-1~deb12u1

sudo apt update && sudo apt install --only-upgrade bind9 dpkg --compare-versions "$(dpkg-query -W -f='${Version}' bind9)" ge "1:9.18.16-1~deb12u1" && echo PATCHED || echo STILL-VULNERABLE

Debian 13 · bind9 · FIXED · 1:9.18.16-1

sudo apt update && sudo apt install --only-upgrade bind9 dpkg --compare-versions "$(dpkg-query -W -f='${Version}' bind9)" ge "1:9.18.16-1" && echo PATCHED || echo STILL-VULNERABLE

RHEL 6 · bind · NOT AFFECTED

RHEL 7 · bind · NOT AFFECTED

RHEL 8 · bind · NOT AFFECTED

RHEL 8 · bind9.16 · NOT AFFECTED

RHEL 9 · bind · NOT AFFECTED

Amazon Linux 2023 · see advisory · FIXED · ALAS2023-2023-240 · source

sudo dnf update --advisory=ALAS2023-2023-240

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-2023-2911?

bind: upgrade to newer than 9.18.15; debian linux: mitigate or apply the listed mitigation; fedora: mitigate or apply the listed mitigation. Exact commands for each OS are on this page.

Is CVE-2023-2911 being exploited?

CVE-2023-2911 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-2023-2911 affect?

CVE-2023-2911 affects bind, debian linux, fedora. Severity is high (CVSS 7.5). If the `recursive-clients` quota is reached on a BIND 9 resolver configured with both `stale-answer-enable yes;` and `stale-answer-client-timeout 0;`, a sequence of serve-stale-related lookups could cause `named` to loop and terminate unexp

How urgent is CVE-2023-2911?

Priority 57/100. High severity; Remotely exploitable, no login, no user action; On your watchlist

Software pages

Debian vulnerabilities · BIND DNS vulnerabilities

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CVE-2006-2073 MEDIUM 5.0 DOWNGRADE Unspecified vulnerability in ISC BIND allows remote attackers to cause a denial of service via a crafted DNS m

References

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