CVE-2023-50868: The Closest Encloser Proof aspect of the DNS protocol (in RFC 5155 when RFC 9276 guidance is skipped) allows r

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HIGH 7.5REMOTEWATCHLISTMITIGATEMITIGATEMITIGATE

CVE-2023-50868 is a high-severity flaw (CVSS 7.5) affecting hci baseboard management controller, active iq unified manager, bootstrap os. Below: why it ranks where it does, which versions are affected, what to do, and the exact commands.

The Closest Encloser Proof aspect of the DNS protocol (in RFC 5155 when RFC 9276 guidance is skipped) allows remote attackers to cause a denial of service (CPU consumption for SHA-1 computations) via DNSSEC responses in a random subdomain attack, aka the "NSEC3" issue. The RFC 5155 specification implies that an algorithm must perform thousands of iterations of a hash function in certain situations.

Why this priority

High severity
EPSS top 1%: 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	7.5 (High)
Attack vector	Network (remote)
Attack complexity	Low
Privileges needed	None
User interaction	None
EPSS exploit chance	74.3% (top 1%)
CISA exploited list	No
Weakness	CWE-400
Published	2024-02-14
Last modified	2026-06-17

Publisher (CNA): MITRE · Vendor: debian · netapp · powerdns · redhat

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

Am I affected?

Timeline

2024-02-14 16:15 UTCPublished CVE record published
2026-06-17 06:40 UTCUpdated Record last modified

netapp hci baseboard management controller 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 hci-baseboard-management-controller || rpm -q hci-baseboard-management-controller || hci-baseboard-management-controller --version

No fixed or unaffected release known

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

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 bootstrap os 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.

powerdns recursor UPGRADE

Affected: < 4.8.5 · >= 4.9.0 and < 4.9.3 · >= 5.0.0 and < 5.0.2

Fixed in: 4.8.5, 4.9.3, 5.0.2

Safe to downgrade to: a release before 4.9.0

1. Check installed version

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

2. UPGRADE to 4.8.5 (Debian / Ubuntu)

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

2. UPGRADE (RHEL / Amazon Linux / Fedora)

sudo dnf upgrade recursor

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 4.9.0 (Debian / Ubuntu)

apt-cache madison recursor sudo apt install recursor=<VERSION_BEFORE_4.9.0> sudo apt-mark hold recursor

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

dnf --showduplicates list recursor sudo dnf downgrade recursor-<VERSION_BEFORE_4.9.0> sudo dnf versionlock add recursor

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.

redhat enterprise linux MITIGATE

Affected: 6.0 · 7.0 · 8.0 · 8.2 · 8.4

Fixed in: no fixed release known

Safe to downgrade to: a release before 6.0

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.

debian debian linux MITIGATE

Affected: 10.0 · 11.0

Fixed in: no fixed release known

Safe to downgrade to: a release before 10.0

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 · sbcl · FIXED · 2.6.10-1.fc46 · FEDORA-2026-feab1a81c6 · source

sudo dnf upgrade --advisory=FEDORA-2026-feab1a81c6

Fedora ELN · python-archspec · FIXED · 0.2.7-1.eln159 · FEDORA-2026-e2a8272db6 · source

sudo dnf upgrade --advisory=FEDORA-2026-e2a8272db6

Ubuntu 20.04 · bind9 · FIXED · 1:9.16.48-0ubuntu0.20.04.1

sudo apt update && sudo apt install --only-upgrade bind9 dpkg --compare-versions "$(dpkg-query -W -f='${Version}' bind9)" ge "1:9.16.48-0ubuntu0.20.04.1" && echo PATCHED || echo STILL-VULNERABLE

Ubuntu 22.04 · bind9 · FIXED · 1:9.18.18-0ubuntu0.22.04.2

sudo apt update && sudo apt install --only-upgrade bind9 dpkg --compare-versions "$(dpkg-query -W -f='${Version}' bind9)" ge "1:9.18.18-0ubuntu0.22.04.2" && echo PATCHED || echo STILL-VULNERABLE

Ubuntu 24.04 · bind9 · FIXED · 1:9.18.24-0ubuntu1

sudo apt update && sudo apt install --only-upgrade bind9 dpkg --compare-versions "$(dpkg-query -W -f='${Version}' bind9)" ge "1:9.18.24-0ubuntu1" && echo PATCHED || echo STILL-VULNERABLE

Ubuntu 24.10 · bind9 · FIXED · 1:9.18.24-0ubuntu1

sudo apt update && sudo apt install --only-upgrade bind9 dpkg --compare-versions "$(dpkg-query -W -f='${Version}' bind9)" ge "1:9.18.24-0ubuntu1" && echo PATCHED || echo STILL-VULNERABLE

Ubuntu 25.04 · bind9 · FIXED · 1:9.18.24-0ubuntu1

sudo apt update && sudo apt install --only-upgrade bind9 dpkg --compare-versions "$(dpkg-query -W -f='${Version}' bind9)" ge "1:9.18.24-0ubuntu1" && echo PATCHED || echo STILL-VULNERABLE

Debian 12 · bind9 · FIXED · 1:9.18.24-1

sudo apt update && sudo apt install --only-upgrade bind9 dpkg --compare-versions "$(dpkg-query -W -f='${Version}' bind9)" ge "1:9.18.24-1" && echo PATCHED || echo STILL-VULNERABLE

Debian 13 · bind9 · FIXED · 1:9.19.21-1

sudo apt update && sudo apt install --only-upgrade bind9 dpkg --compare-versions "$(dpkg-query -W -f='${Version}' bind9)" ge "1:9.19.21-1" && echo PATCHED || echo STILL-VULNERABLE

Debian 12 · dnsjava · NO FIX YET

Debian 13 · dnsjava · FIXED · 3.6.2-1

sudo apt update && sudo apt install --only-upgrade dnsjava dpkg --compare-versions "$(dpkg-query -W -f='${Version}' dnsjava)" ge "3.6.2-1" && echo PATCHED || echo STILL-VULNERABLE

RHEL 6 Extended Lifecycle Support - EXTENSION · bind · FIXED · bind-9.8.2-0.68.rc1.el6_10.14

sudo dnf upgrade --advisory=RHSA-2025:0039 rpm -q bind

RHEL 6 Extended Lifecycle Support - EXTENSION · bind-dyndb-ldap · FIXED · bind-dyndb-ldap-2.3-8.el6_10.1

sudo dnf upgrade --advisory=RHSA-2025:0039 rpm -q bind-dyndb-ldap

RHEL 7 · bind · FIXED · bind-9.11.4-26.P2.el7_9.16

sudo dnf upgrade --advisory=RHSA-2024:3741 rpm -q bind

RHEL 7 · bind-dyndb-ldap · FIXED · bind-dyndb-ldap-11.1-7.el7_9.1

sudo dnf upgrade --advisory=RHSA-2024:3741 rpm -q bind-dyndb-ldap

RHEL 7 · dhcp · FIXED · dhcp-4.2.5-83.el7_9.2

sudo dnf upgrade --advisory=RHSA-2024:3741 rpm -q dhcp

Alpine 3.20 · bind · FIXED · bind-9.18.24-r0

apk add --upgrade bind apk info -v bind

Alpine 3.20 · dnsmasq · FIXED · dnsmasq-2.90-r0

apk add --upgrade dnsmasq apk info -v dnsmasq

Alpine 3.20 · unbound · FIXED · unbound-1.19.1-r0

apk add --upgrade unbound apk info -v unbound

Alpine 3.20 · knot-resolver · FIXED · knot-resolver-5.7.1-r0

apk add --upgrade knot-resolver apk info -v knot-resolver

Amazon Linux 2023 · see advisory · FIXED · ALAS2023-2024-553 · source

sudo dnf update --advisory=ALAS2023-2024-553

Amazon Linux 2 · see advisory · FIXED · ALAS2-2024-2530 · source

sudo yum update --advisory=ALAS2-2024-2530

Public exploits and detection

Public code exists for this CVE. Treat unpatched systems as at risk, and only run PoCs in a lab.

GitHub PoC: Goethe-Universitat-Cybersecurity/NSEC3-Encloser-Attack (6 stars)

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-2023-50868?

hci baseboard management controller: mitigate or apply the listed mitigation; active iq unified manager: mitigate or apply the listed mitigation; bootstrap os: mitigate or apply the listed mitigation. Exact commands for each OS are on this page.

Is CVE-2023-50868 being exploited?

CVE-2023-50868 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-2023-50868 affect?

CVE-2023-50868 affects hci baseboard management controller, active iq unified manager, bootstrap os. Severity is high (CVSS 7.5). The Closest Encloser Proof aspect of the DNS protocol (in RFC 5155 when RFC 9276 guidance is skipped) allows remote attackers to cause a denial of service (CPU consumption for SHA-1 computations) via DNSSEC responses in a random subdomain a

How urgent is CVE-2023-50868?

Priority 66/100. High severity; EPSS top 1%: very likely to be exploited; Public exploit reference; Remotely exploitable, no login, no user action; On your watchlist

Software pages

Debian vulnerabilities · Bootstrap vulnerabilities

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References

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