CVE-2026-23243
Description
A flaw was found in the Linux kernel's Remote Direct Memory Access (RDMA) umad (User Mode Access Device) component. A local user can exploit this vulnerability by manipulating input, causing an integer underflow that leads to an out-of-bounds memory write. This memory corruption can result in a denial of service (DoS) by crashing the system, and may also lead to limited information disclosure or data integrity issues.
Statement
This bug is a kernel out-of-bounds write in the RDMA umad write path caused by a user-controlled length calculation that could underflow and pass an invalid data_len into MAD send buffer creation. A local user with access to the umad interface can trigger the issue by supplying mismatched MAD and RMPP header sizes, which leads to an out-of-bounds memset in the send MAD allocation path and can corrupt kernel memory.
Mitigation
To mitigate this issue, prevent module ib_umad from being loaded. Please see https://access.redhat.com/solutions/41278 for how to blacklist a kernel module to prevent it from loading automatically.
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 | 7.3 | 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 | Low | 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:L/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,Availability,Confidentiality
Technical Impact: DoS: Crash, Exit, or Restart; Execute Unauthorized Code or Commands; Read Memory; Modify Memory
If the incorrect calculation is used in the context of memory allocation, then the software may create a buffer that is smaller or larger than expected. If the allocated buffer is smaller than expected, this could lead to an out-of-bounds read or write (CWE-119), possibly causing a crash, allowing arbitrary code execution, or exposing sensitive data.
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