CVE-2026-107364
Description
In all released versions of MIT krb5, an unauthenticated attacker can cause a KDC process to perform a large read overrun, likely causing the process to terminate.
Statement
This vulnerability is rated as Important severity because an unauthenticated remote network attacker can crash the Kerberos Key Distribution Center (KDC) daemon, leading to an immediate denial of service across the entire authentication realm. In Red Hat Enterprise Linux and related offerings, the KDC service is not enabled by default on standard deployments and is typically confined to dedicated identity management servers (such as FreeIPA or standalone KDCs). Standard endpoints and systems operating solely as Kerberos clients do not process incoming KDC requests and are not directly vulnerable to this service interruption.
Mitigation
Restrict network access to the Kerberos Key Distribution Center (KDC) ports (88 UDP/TCP) to trusted client networks, or disable the KDC service on systems not operating as identity controllers.
To stop and disable the KDC service on systems where it is not required:
systemctl stop krb5kdc
systemctl disable krb5kdc
To restrict network access to an authorized client subnet (e.g., 192.168.1.0/24) using firewalld:
firewall-cmd --permanent --zone=public --remove-service=kerberos
firewall-cmd --permanent --zone=public --add-rich-rule='rule family="ipv4" source address="192.168.1.0/24" service name="kerberos" accept'
firewall-cmd --reload
Caveat: Disabling the service or blocking network traffic prevents unlisted clients from obtaining Kerberos tickets, which will disrupt authentication and single sign-on services in the realm.
Warning: Reloading firewall rules or stopping the KDC service will immediately terminate active Kerberos connections and fail in-flight ticket requests.
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 | 7.5 | N/A | N/A |
| Attack Vector | Network | N/A | N/A |
| Attack Complexity | Low | N/A | N/A |
| Privileges Required | None | 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:N/UI:N/S:U/C:N/I:N/A:H
Understanding the Weakness (CWE)
Confidentiality
Technical Impact: Read Memory
An attacker could get secret values such as cryptographic keys, PII, memory addresses, or other information that could be used in additional attacks.
Confidentiality
Technical Impact: Bypass Protection Mechanism
Out-of-bounds memory could contain memory addresses or other information that can be used to bypass ASLR and other protection mechanisms in order to improve the reliability of exploiting a separate weakness for code execution.
Availability
Technical Impact: DoS: Crash, Exit, or Restart
An attacker could cause a segmentation fault or crash by causing memory to be read outside of the bounds of the buffer. This is especially likely when the code reads a variable amount of data and assumes that a sentinel exists to stop the read operation, such as a NUL in a string.
Other
Technical Impact: Varies by Context
The read operation could produce other undefined or unexpected results.
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