CVE-2026-89630
Description
A flaw was found in the Linux kernel's Server Message Block (SMB) client. An incorrect calculation of the data_offset bound in the is_valid_oplock_break() function can lead to a read overflow. This vulnerability allows a malicious SMB server to potentially trigger an out-of-bounds read, which could result in information disclosure or a denial of service.
Statement
An out of bounds read in the SMB client oplock break validation path can occur because is_valid_oplock_break uses an ineffective DataOffset bound after the RFC1002 preamble accounting changed. A malicious or compromised SMB server can send a crafted SMB1 notification or oplock related response with an invalid DataOffset, causing the Linux client kernel to read beyond the received SMB message and potentially crash. For the CVSS the PR:N because the attacker does not need privileges on the victim and only needs control of or ability to impersonate an SMB server that the client communicates with. UI:R is used because the client normally has to mount or connect to the malicious server or an already configured share must point to a compromised endpoint. The issue is network reachable from server to client. Impact is at least denial of service via kernel crash, with limited confidentiality impact considered only in the paranoid score due to the out of bounds read primitive.
Mitigation
Mitigation for this issue is either not available or the currently available options don't meet the Red Hat Product Security criteria comprising ease of use and deployment, applicability to widespread installation base or stability.
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 | 6.5 | N/A | 9.1 |
| Attack Vector | Network | N/A | Network |
| Attack Complexity | Low | N/A | Low |
| Privileges Required | None | N/A | None |
| User Interaction | Required | N/A | None |
| Scope | Unchanged | N/A | Unchanged |
| Confidentiality | None | N/A | High |
| 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:R/S:U/C:N/I:N/A:H
cve.org: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:H
Understanding the Weakness (CWE)
Availability
Technical Impact: DoS: Crash, Exit, or Restart; DoS: Resource Consumption (CPU); DoS: Resource Consumption (Memory)
An attacker could provide unexpected values and cause a program crash or arbitrary control of resource allocation, leading to excessive consumption of resources such as memory and CPU.
Confidentiality
Technical Impact: Read Memory; Read Files or Directories
An attacker could read confidential data if they are able to control resource references.
Integrity,Confidentiality,Availability
Technical Impact: Modify Memory; Execute Unauthorized Code or Commands
An attacker could use malicious input to modify data or possibly alter control flow in unexpected ways, including arbitrary command execution.
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