CVE-2021-36222: ec_verify in kdc/kdc_preauth_ec.c in the Key Distribution Center (KDC) in MIT Kerberos 5 (aka krb5) before 1.1

This week

HIGH 7.5REMOTEWATCHLISTUPGRADEMITIGATEMITIGATE

CVE-2021-36222 is a high-severity flaw (CVSS 7.5) affecting kerberos 5, debian linux, active iq unified manager. Below: why it ranks where it does, which versions are affected, what to do, and the exact commands.

ec_verify in kdc/kdc_preauth_ec.c in the Key Distribution Center (KDC) in MIT Kerberos 5 (aka krb5) before 1.18.4 and 1.19.x before 1.19.2 allows remote attackers to cause a NULL pointer dereference and daemon crash. This occurs because a return value is not properly managed in a certain situation.

Why this priority

High severity
EPSS top 4%: very likely to be exploited
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	10.5% (top 4%)
CISA exploited list	No
Weakness	CWE-476
Published	2021-07-22
Last modified	2026-10-14

Publisher (CNA): MITRE · Vendor: debian · mit · netapp

Last updated 2026-10-14 · Sources: CVE Program, NVD, CISA KEV, EPSS and vendor advisories · How we score

Am I affected?

Timeline

2021-07-22 18:15 UTCPublished CVE record published
2026-10-14 12:17 UTCUpdated Record last modified

mit kerberos 5 UPGRADE

Affected: < 1.18.4 · >= 1.19.0 and < 1.19.2

Fixed in: 1.18.4, 1.19.2

Safe to downgrade to: a release before 1.19.0

1. Check installed version

apt-cache policy kerberos-5 || rpm -q kerberos-5 || kerberos-5 --version

2. UPGRADE to 1.18.4 (Debian / Ubuntu)

sudo apt update && sudo apt install --only-upgrade kerberos-5

2. UPGRADE (RHEL / Amazon Linux / Fedora)

sudo dnf upgrade kerberos-5

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 1.19.0 (Debian / Ubuntu)

apt-cache madison kerberos-5 sudo apt install kerberos-5=<VERSION_BEFORE_1.19.0> sudo apt-mark hold kerberos-5

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

dnf --showduplicates list kerberos-5 sudo dnf downgrade kerberos-5-<VERSION_BEFORE_1.19.0> sudo dnf versionlock add kerberos-5

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: 10.0

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.

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 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 oncommand insight 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 oncommand-insight || rpm -q oncommand-insight || oncommand-insight --version

No fixed or unaffected release known

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

netapp oncommand workflow automation 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 oncommand-workflow-automation || rpm -q oncommand-workflow-automation || oncommand-workflow-automation --version

No fixed or unaffected release known

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

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-2021-36222?

kerberos 5: upgrade to 1.18.4, 1.19.2; debian linux: mitigate or apply the listed mitigation; active iq unified manager: mitigate or apply the listed mitigation. Exact commands for each OS are on this page.

Is CVE-2021-36222 being exploited?

CVE-2021-36222 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-2021-36222 affect?

CVE-2021-36222 affects kerberos 5, debian linux, active iq unified manager. Severity is high (CVSS 7.5). ec_verify in kdc/kdc_preauth_ec.c in the Key Distribution Center (KDC) in MIT Kerberos 5 (aka krb5) before 1.18.4 and 1.19.x before 1.19.2 allows remote attackers to cause a NULL pointer dereference and daemon crash. This occurs because a r

How urgent is CVE-2021-36222?

Priority 60/100. High severity; EPSS top 4%: very likely to be exploited; Remotely exploitable, no login, no user action; On your watchlist

Software pages

Debian vulnerabilities

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References

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