CVE-2026-46243
Description
A privilege escalation vulnerability was found in the Linux kernel's CIFS client implementation. This could allow a local attacker to impersonate other users, bypass authentication in SMB mount operations, and potentially gain unauthorized access to network file shares or escalate privileges.
Security Bulletin
Statement
This issue is classified as Important severity primarily because a low-privileged local user can achieve full privilege escalation to root without any user interaction. The attack requires local access, which prevents remote exploitation and is the primary factor keeping the rating at Important rather than Critical.
Exploitation requires three components to be present on the system: the cifs kernel module (loaded or loadable), the cifs-utils package with its default cifs.spnego request-key rule, and the ability to create unprivileged user and mount namespaces. All three must be present for the attack chain to succeed. Environments that do not use SMB/CIFS file shares or Active Directory integration are unlikely to have cifs-utils installed, reducing their exposure.
In OpenShift Container Platform 4, this flaw is rated Low. The default restricted-v2 Security Context Constraint (SCC) sets allowPrivilegeEscalation: false on all pods, which causes the kernel to ignore setuid file bits, preventing privilege escalation. Under non-default SCCs such as anyuid that permit privilege escalation, the vulnerability is constrained by PID and mount namespace isolation to the container's own filesystem. An attacker would only be able to escalate privileges within the container, not on the host or across pods.
Mitigation
See the security bulletin for a detailed mitigation procedure.
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).
CVSS v3 Score Breakdown
| Red Hat | NVD | cve.org | |
|---|---|---|---|
| Base Score | 7.8 | N/A | 7.8 |
| Attack Vector | Local | N/A | Local |
| Attack Complexity | Low | N/A | Low |
| Privileges Required | Low | N/A | Low |
| User Interaction | None | N/A | None |
| Scope | Unchanged | N/A | Unchanged |
| Confidentiality | High | N/A | High |
| Integrity Impact | High | N/A | High |
| Availability Impact | High | N/A | High |
Vector
Red Hat: CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
cve.org: CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
Understanding the Weakness (CWE)
Confidentiality
Technical Impact: Read Memory
If the expired pointer is used in a read operation, an attacker might be able to control data read in by the application.
Availability
Technical Impact: DoS: Crash, Exit, or Restart
If the expired pointer references a memory location that is not accessible to the product, or points to a location that is "malformed" (such as NULL) or larger than expected by a read or write operation, then a crash may occur.
Integrity,Confidentiality,Availability
Technical Impact: Execute Unauthorized Code or Commands
If the expired pointer is used in a function call, or points to unexpected data in a write operation, then code execution may be possible.
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