CVE-2021-36222Public exploitNetwork attack vector

Daemon crash via overwritten error return

Published Jul 22, 2021 · Updated Aug 4, 2024

NULL pointer dereference in the MIT Kerberos 5 KDC before 1.18.4 and 1.19.x before 1.19.2 allows remote attackers to crash the daemon. In ec_verify(), k5memdup0() overwrites an earlier error return when no FAST armor key exists, allowing krb5_c_fx_cf2_simple() to dereference that NULL key. An unauthenticated PA-ENCRYPTED-CHALLENGE request sent without FAST is sufficient, interrupting KDC authentication service until the daemon restarts.

CVSS severity7.5
High
EPSS probability10.28%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

NULL pointer dereference in the MIT Kerberos 5 KDC before 1.18.4 and 1.19.x before 1.19.2 allows remote attackers to crash the daemon. In ec_verify(), k5memdup0() overwrites an earlier error return when no FAST armor key exists, allowing krb5_c_fx_cf2_simple() to dereference that NULL key. An unauthenticated PA-ENCRYPTED-CHALLENGE request sent without FAST is sufficient, interrupting KDC authentication service until the daemon restarts.

The record

CVE
CVE-2021-36222
Published
Jul 22, 2021
Updated
Aug 4, 2024
Vendor
Unknown vendor
Product
Unknown product
Classifications
CWE-476, T1499.004
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Jul 22, 2021CVE publishedPublication date reported by the CVE source.
  2. Aug 4, 2024Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

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Is a vulnerable build present?

Affected buildAffected product and version details are unavailable.

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

Affected products and versions are unavailable in this record.

Published CVSS scores

7.5NIST NVDCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
5.0NIST NVDAV:N/AC:L/Au:N/C:N/I:N/A:P

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.

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No observations available

Sep 10, 2026Sep 16, 2026
Latest reporting daySep 16, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectornetwork
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitPublished

Weakness, pattern, technique

CWE-476NULL Pointer Dereference
T1499.004Application or System Exploitation

Public exploit references

Labels summarize the accepted research assessment. They do not indicate a test against your environment.

Technologies

Your stack

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Your stack

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