CVE-2026-112318
Description
The policy RPC stubs in kadmin/server/server_stubs.c in MIT Kerberos 5 (aka krb5) 1.5.3 and later do not reject a NULL policy name decoded by xdr_nullstring(), which allows remote authenticated users to cause a denial of service (kadmind crash via NULL pointer dereference) by sending a policy request with an empty policy name that reaches authorization checks or logging code.
Statement
This vulnerability is rated as an Important severity flaw because an authenticated remote network attacker can crash the Kerberos administrative daemon, resulting in a denial of service for administrative operations. The kadmind service is not enabled by default across Red Hat Enterprise Linux systems and is typically isolated to dedicated KDC administration hosts. While standard ticket-granting and authentication services provided by krb5kdc remain operational, terminating kadmind prevents users and administrators from modifying account policies, provisioning keytabs, or changing passwords until the service is restarted.
Mitigation
Restrict network access to kadmind to trusted hosts, or disable it in favor of kadmin.local server-side command line tool for administration operations if possible.
Common Vulnerability Scoring System (CVSS) Score Details
Info alert:Important note
CVSS scores for open source components depend on vendor-specific factors (e.g. version or build chain). Therefore, Red Hat's score and impact rating can be different from NVD and other vendors. Red Hat remains the authoritative CVE Naming Authority (CNA) source for its products and services (see Red Hat classifications).
The following CVSS metrics and score provided are preliminary and subject to review.
CVSS v3 Score Breakdown
| Red Hat | NVD | cve.org | |
|---|---|---|---|
| Base Score | 6.5 | N/A | N/A |
| Attack Vector | Network | N/A | N/A |
| Attack Complexity | Low | N/A | N/A |
| Privileges Required | Low | N/A | N/A |
| User Interaction | None | N/A | N/A |
| Scope | Unchanged | N/A | N/A |
| Confidentiality | None | N/A | N/A |
| Integrity Impact | None | N/A | N/A |
| Availability Impact | High | N/A | N/A |
Vector
Red Hat: CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H
Understanding the Weakness (CWE)
Availability
Technical Impact: DoS: Crash, Exit, or Restart
NULL pointer dereferences usually result in the failure of the process unless exception handling (on some platforms) is available and implemented. Even when exception handling is being used, it can still be very difficult to return the software to a safe state of operation.
Integrity,Confidentiality
Technical Impact: Execute Unauthorized Code or Commands; Read Memory; Modify Memory
In rare circumstances, when NULL is equivalent to the 0x0 memory address and privileged code can access it, then writing or reading memory is possible, which may lead to code execution.
Acknowledgements
This issue was discovered by Found by AISLE in partnership with Red Hat.
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