CVE-2026-40355Public exploitNetwork attack vector

Unauthenticated process crash via unchecked NegoEx vector

Published Apr 28, 2026 · Updated Apr 28, 2026

NULL pointer dereference in MIT Kerberos 5 1.18 through 1.22.2 allows remote attackers to terminate GSS-API application processes. The NegoEx parse_nego_message function dereferences the second vector_base result without checking whether crafted extension offsets and counts made it NULL. Exploitation requires a GSS-API acceptor and a registered NegoEx mechanism, and it crashes only the process handling the token.

CVSS severity5.9
Medium
EPSS probability0.61%
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 MIT Kerberos 5 1.18 through 1.22.2 allows remote attackers to terminate GSS-API application processes. The NegoEx parse_nego_message function dereferences the second vector_base result without checking whether crafted extension offsets and counts made it NULL. Exploitation requires a GSS-API acceptor and a registered NegoEx mechanism, and it crashes only the process handling the token.

The record

CVE
CVE-2026-40355
Published
Apr 28, 2026
Updated
Apr 28, 2026
Vendor
Massachusetts Institute of Technology
Product
Kerberos 5
Classifications
CWE-476, T1499.004
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Apr 28, 2026CVE publishedPublication date reported by the CVE source.
  2. Apr 28, 2026Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

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Is a vulnerable build present?

Compare these published version ranges with your installed build and any vendor patches.

  1. Affected versionversion=1.18 <1.22.3

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

Massachusetts Institute of Technology · Kerberos 5version=1.18 <1.22.3

Published CVSS scores

5.9MITRECVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:H
7.5NIST NVDCVSS:3.1/AV:N/AC:L/PR:N/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.

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No observations available

Sep 9, 2026Sep 15, 2026
Latest reporting daySep 15, 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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