RHSA-2026:12220
Vulnerability from csaf_redhat - Published: 2026-04-30 09:30 - Updated: 2026-05-04 14:56Summary
Red Hat Security Advisory: Red Hat Hardened Images RPMs bug fix and enhancement update
Severity
Important
Notes
Topic: An update for Red Hat Hardened Images RPMs is now available.
Details: This update includes the following RPMs:
krb5:
* krb5-devel-1.22.2-7.hum1 (aarch64, x86_64)
* krb5-libs-1.22.2-7.hum1 (aarch64, x86_64)
* krb5-pkinit-1.22.2-7.hum1 (aarch64, x86_64)
* krb5-server-1.22.2-7.hum1 (aarch64, x86_64)
* krb5-server-ldap-1.22.2-7.hum1 (aarch64, x86_64)
* krb5-tests-1.22.2-7.hum1 (aarch64, x86_64)
* krb5-workstation-1.22.2-7.hum1 (aarch64, x86_64)
* krb5-xrealmauthz-1.22.2-7.hum1 (aarch64, x86_64)
* libkadm5-1.22.2-7.hum1 (aarch64, x86_64)
* krb5-1.22.2-7.hum1.src (src)
Terms of Use: This content is licensed under the Creative Commons Attribution 4.0 International License (https://creativecommons.org/licenses/by/4.0/). If you distribute this content, or a modified version of it, you must provide attribution to Red Hat Inc. and provide a link to the original.
A flaw was found in MIT Kerberos 5 (krb5). An unauthenticated remote attacker can exploit a NULL pointer dereference vulnerability by calling `gss_accept_sec_context()` on a system with a NegoEx mechanism registered. This can lead to the termination of the process, resulting in a Denial of Service (DoS).
5.9 (Medium)
Vendor Fix
For details on how to apply this update, which includes the changes described in this advisory, refer to:
https://images.redhat.com/
https://access.redhat.com/errata/RHSA-2026:12220
Workaround
To mitigate this issue, remove the NegoEx mechanism registration from the system's GSSAPI configuration if it is not required. This can typically be achieved by removing or commenting out the relevant entry in `/etc/gss/mech`. A restart of services utilizing Kerberos might be necessary for the changes to take effect, which could impact Kerberos-dependent functionality.
A flaw was found in MIT Kerberos 5 (krb5). An unauthenticated remote attacker can exploit an integer underflow and an out-of-bounds read vulnerability by calling `gss_accept_sec_context()` on a system with a NegoEx mechanism registered. This can lead to the process terminating, resulting in a Denial of Service (DoS).
5.9 (Medium)
Vendor Fix
For details on how to apply this update, which includes the changes described in this advisory, refer to:
https://images.redhat.com/
https://access.redhat.com/errata/RHSA-2026:12220
Workaround
To mitigate this issue, ensure that the NegoEx mechanism is not registered in the `/etc/gss/mech` configuration file. Removing the corresponding entry from this file will prevent the vulnerable code path from being activated. This action may impact services that rely on the NegoEx GSS-API mechanism. A restart of affected Kerberos-dependent services may be required for the change to take effect.
References
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"text": "This update includes the following RPMs:\n\nkrb5:\n * krb5-devel-1.22.2-7.hum1 (aarch64, x86_64)\n * krb5-libs-1.22.2-7.hum1 (aarch64, x86_64)\n * krb5-pkinit-1.22.2-7.hum1 (aarch64, x86_64)\n * krb5-server-1.22.2-7.hum1 (aarch64, x86_64)\n * krb5-server-ldap-1.22.2-7.hum1 (aarch64, x86_64)\n * krb5-tests-1.22.2-7.hum1 (aarch64, x86_64)\n * krb5-workstation-1.22.2-7.hum1 (aarch64, x86_64)\n * krb5-xrealmauthz-1.22.2-7.hum1 (aarch64, x86_64)\n * libkadm5-1.22.2-7.hum1 (aarch64, x86_64)\n * krb5-1.22.2-7.hum1.src (src)",
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"ids": [
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"notes": [
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"title": "Vulnerability description"
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"title": "Vulnerability summary"
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"text": "Moderate: This flaw allows an unauthenticated remote attacker to cause a Denial of Service in MIT Kerberos 5 by triggering a NULL pointer dereference. Exploitation requires the NegoEx mechanism to be explicitly registered in the system\u0027s GSSAPI configuration, which is not a default state in all Red Hat environments.",
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{
"category": "external",
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"url": "https://cems.fun/2026/04/27/krb5-two-unauthenticated-network-vulnerabilities.html"
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"title": "krb5: MIT Kerberos 5: Denial of Service via NULL pointer dereference in NegoEx mechanism"
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"privilegesRequired": "NONE",
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"title": "krb5: MIT Kerberos 5 (krb5): Denial of Service via integer underflow and out-of-bounds read"
}
]
}
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Experimental. This forecast is provided for visualization only and may change without notice. Do not use it for operational decisions.
Forecast uses a logistic model when the trend is rising, or an exponential decay model when the trend is falling. Fitted via linearized least squares.
Sightings
| Author | Source | Type | Date | Other |
|---|
Nomenclature
- Seen: The vulnerability was mentioned, discussed, or observed by the user.
- Confirmed: The vulnerability has been validated from an analyst's perspective.
- Published Proof of Concept: A public proof of concept is available for this vulnerability.
- Exploited: The vulnerability was observed as exploited by the user who reported the sighting.
- Patched: The vulnerability was observed as successfully patched by the user who reported the sighting.
- Not exploited: The vulnerability was not observed as exploited by the user who reported the sighting.
- Not confirmed: The user expressed doubt about the validity of the vulnerability.
- Not patched: The vulnerability was not observed as successfully patched by the user who reported the sighting.
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