CVE-2021-37750Network attack vector

Authenticated KDC crash via missing FAST server field

Published Aug 23, 2021 · Updated Aug 4, 2024

NULL pointer dereference in the MIT Kerberos 5 KDC before 1.18.5 and 1.19.x before 1.19.3 allows remote authenticated users to crash the KDC. After decoding a FAST inner TGS request, process_tgs_req reads sprinc->realm for get_local_tgt even when the request omitted the server principal. A valid Kerberos identity is required; the crafted request terminates the KDC and interrupts authentication service without exposing or modifying data.

CVSS severity6.5
Medium
EPSS probability2.17%
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 1.18.5 and 1.19.x before 1.19.3 allows remote authenticated users to crash the KDC. After decoding a FAST inner TGS request, process_tgs_req reads sprinc->realm for get_local_tgt even when the request omitted the server principal. A valid Kerberos identity is required; the crafted request terminates the KDC and interrupts authentication service without exposing or modifying data.

The record

CVE
CVE-2021-37750
Published
Aug 23, 2021
Updated
Aug 4, 2024
Vendor
Unknown vendor
Product
Unknown product
Classifications
CWE-476, T1499.004
Attack vector
network
Privileges
authenticated

Timeline

How it unfolded

  1. Aug 23, 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 privilegesauthenticated

What is affected?

Affected products and versions are unavailable in this record.

Published CVSS scores

4.0NIST NVDAV:N/AC:L/Au:S/C:N/I:N/A:P
6.5NIST NVDCVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H

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.

Daily unique IPsNo honeypot observations are available for this CVE in the selected window.

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
Privilegesauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

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

Public exploit references

No public exploit references are available in this record.

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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