CVE-2026-64597
Description
A flaw was found in the Linux kernel's Server Message Block (SMB) client. A vulnerability exists in the SMB2_close() replay mechanism where a response buffer can be freed twice. This double-free condition can lead to memory corruption, potentially resulting in a denial of service or the execution of arbitrary code.
Statement
A flaw was found in the Linux kernel's SMB client. A double-free vulnerability exists in the SMB2_close() replay mechanism where a response buffer's bookkeeping state can become stale across retry attempts, leading to the same buffer being freed twice. This could result in memory corruption, potentially causing a denial of service (kernel panic) or other undefined behavior. Exploitation requires the victim system to connect to a malicious or compromised SMB server.
Mitigation
If SMB/CIFS client functionality is not required, the 'cifs' kernel module can be blocklisted to prevent it from loading. Systems that do not mount SMB/CIFS shares are not affected. For systems that require SMB client access, ensure connections are only made to trusted SMB servers.
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 | N/A | 9.8 |
| Attack Vector | Local | N/A | Network |
| Attack Complexity | High | N/A | Low |
| Privileges Required | Low | N/A | None |
| 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:H/PR:L/UI:N/S:U/C:H/I:H/A:H
cve.org: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
Understanding the Weakness (CWE)
Integrity,Confidentiality,Availability
Technical Impact: Modify Memory; Execute Unauthorized Code or Commands
When a program calls free() twice with the same argument, the program's memory management data structures may become corrupted, potentially leading to the reading or modification of unexpected memory addresses. This corruption can cause the program to crash or, in some circumstances, cause two later calls to malloc() to return the same pointer. If malloc() returns the same value twice and the program later gives the attacker control over the data that is written into this doubly-allocated memory, the program becomes vulnerable to a buffer overflow attack. Doubly freeing memory may result in a write-what-where condition, allowing an attacker to execute arbitrary code.
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