CVE-2026-99110
Description
A flaw was found in the Linux kernel's Common Internet File System (CIFS) client. When converting a POSIX Access Control List (ACL) to the network wire format, the kernel verifies the ACL against an extended attribute size calculation instead of the larger network format size, leading to a heap-based buffer overflow. A local user can exploit this vulnerability by setting an access control list on a mounted share to achieve privilege escalation, execute arbitrary code, or crash the system, causing a Denial of Service (DoS).
Statement
This vulnerability is rated as Important severity because an unprivileged local user could leverage heap corruption in kernel space to achieve root privileges or trigger an operating system denial of service. Exploitation requires that a CIFS/SMB network share is mounted and that the local attacker possesses permissions to set file attributes on the remote filesystem. Standard Red Hat Enterprise Linux configurations are not exposed unless an SMB share is actively mounted with POSIX ACL handling enabled.
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 |
| Attack Vector | Local | N/A | Local |
| Attack Complexity | Low | N/A | High |
| 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:H/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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