CVE-2026-99109
Description
A flaw was found in the Linux kernel's SMB client. This flaw allows a local, unprivileged user to cause a Denial of Service (DoS) or potentially escalate privileges. The CIFSSMBSetEA() function fails to verify that an extended attribute value fits within the allocated request buffer before copying the data. By setting a large extended attribute on a Server Message Block (SMB) mount, an attacker can trigger a heap out-of-bounds write and crash the system.
Statement
This vulnerability is rated as Important because an unprivileged local user with write access to an active legacy SMB share can corrupt kernel slab memory, potentially achieving local privilege escalation or crashing the host. Exploitation requires an active SMB 1.0 filesystem mount accessible to the attacker, whereas Red Hat Enterprise Linux configurations default to SMB 2.1 or newer protocol versions. Consequently, environments that do not mount remote shares using the deprecated CIFS protocol are not susceptible to this attack.
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 | 7.8 | 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)
Integrity
Technical Impact: Modify Memory; Execute Unauthorized Code or Commands
Write operations could cause memory corruption. In some cases, an adversary can modify control data such as return addresses in order to execute unexpected code.
Availability
Technical Impact: DoS: Crash, Exit, or Restart
Attempting to access out-of-range, invalid, or unauthorized memory could cause the product to crash.
Other
Technical Impact: Unexpected State
Subsequent write operations can produce undefined or unexpected results.
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