CVE-2026-3238
Description
A flaw was found in Samba’s WINS server component when running as an Active Directory Domain Controller. The WINS protocol handlers for certain request types did not properly validate incoming packets, allowing an unauthenticated remote attacker to trigger a NULL pointer dereference and crash the WINS service using specially crafted UDP packets.
Statement
This vulnerability affects the WINS server functionality in Samba Active Directory Domain Controller deployments.
A remote unauthenticated attacker may send specially crafted WINS packets that cause the WINS service to crash, resulting in denial of service. Although the service may automatically restart, the attack is trivial to repeat and can effectively make the WINS service continuously unavailable.
The vulnerable WINS functionality is not enabled by default and requires explicit activation using: "wins support = yes" setting in the [global] section of the smb.conf file.
The Samba package as shipped with Red Hat Enterprise Linux and other products is not affected by this issue as Red Hat doesn't provide the AD Domain Controller capability with it.
Mitigation
As a workaround, deployments that do not strictly require Samba-provided WINS functionality should disable WINS support by removing:
wins support = yesfrom the Samba configuration.
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 | 7.5 |
| Attack Vector | Network | N/A | Network |
| Attack Complexity | Low | N/A | Low |
| Privileges Required | None | N/A | None |
| User Interaction | None | N/A | None |
| Scope | Unchanged | N/A | Unchanged |
| Confidentiality | None | N/A | None |
| Integrity Impact | None | N/A | None |
| Availability Impact | High | N/A | High |
Vector
Red Hat: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
cve.org: CVSS:3.1/AV:N/AC:L/PR:N/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
Red Hat would like to thank Arad Inbar (DREAM Security Research Team), Ben Grinberg (DREAM Security Research Team), Erez Cohen (DREAM Security Research Team), and Nir Somech (DREAM Security Research Team) for reporting this issue.
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