CVE-2022-44640: Heimdal before 7.7.1 allows remote attackers to execute arbitrary code because of an invalid free in the ASN.1

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CRITICAL 9.8REMOTEUPGRADEUPGRADE

CVE-2022-44640 is a critical-severity flaw (CVSS 9.8) affecting heimdal, samba. Below: why it ranks where it does, which versions are affected, what to do, and the exact commands.

Heimdal before 7.7.1 allows remote attackers to execute arbitrary code because of an invalid free in the ASN.1 codec used by the Key Distribution Center (KDC).

Why this priority

Critical severity
Remotely exploitable, no login, no user action

A fixed release or distro patch exists.

Risk facts

CVSS score	9.8 (Critical)
Attack vector	Network (remote)
Attack complexity	Low
Privileges needed	None
User interaction	None
EPSS exploit chance	2.3% (top 16%)
CISA exploited list	No
Weakness	CWE-415
Published	2022-12-25
Last modified	2026-06-17

Publisher (CNA): MITRE · Vendor: heimdal project · samba

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

Am I affected?

Timeline

2022-12-25 05:15 UTCPublished CVE record published
2026-06-17 05:08 UTCUpdated Record last modified

heimdal project heimdal UPGRADE

Affected: < 7.7.1

Fixed in: 7.7.1

Safe to downgrade to: no unaffected older release

1. Check installed version

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

2. UPGRADE to 7.7.1 (Debian / Ubuntu)

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

2. UPGRADE (RHEL / Amazon Linux / Fedora)

sudo dnf upgrade heimdal

Note

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

samba samba UPGRADE

Affected: >= 4.15.0 and < 4.15.3 · >= 4.16.0 and < 4.16.8 · >= 4.17.0 and < 4.17.4

Fixed in: 4.15.3, 4.16.8, 4.17.4

Safe to downgrade to: a release before 4.15.0

1. Check installed version

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

2. UPGRADE to 4.15.3 (Debian / Ubuntu)

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

2. UPGRADE (RHEL / Amazon Linux / Fedora)

sudo dnf upgrade samba

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 4.15.0 (Debian / Ubuntu)

apt-cache madison samba sudo apt install samba=<VERSION_BEFORE_4.15.0> sudo apt-mark hold samba

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

dnf --showduplicates list samba sudo dnf downgrade samba-<VERSION_BEFORE_4.15.0> sudo dnf versionlock add samba

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.

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-2022-44640?

heimdal: upgrade to 7.7.1; samba: upgrade to 4.15.3, 4.16.8, 4.17.4. Exact commands for each OS are on this page.

Is CVE-2022-44640 being exploited?

CVE-2022-44640 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-2022-44640 affect?

CVE-2022-44640 affects heimdal, samba. Severity is critical (CVSS 9.8). Heimdal before 7.7.1 allows remote attackers to execute arbitrary code because of an invalid free in the ASN.1 codec used by the Key Distribution Center (KDC).

How urgent is CVE-2022-44640?

Priority 60/100. Critical severity; Remotely exploitable, no login, no user action

Software pages

Samba vulnerabilities

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References

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