CVE-2026-89505

Received Received - Intake

Null Pointer Dereference in Linux Kernel RDMA/uverbs

Publication date: 2026-09-11

Last updated on: 2026-09-11

Assigner: kernel.org

Description

In the Linux kernel, the following vulnerability has been resolved: RDMA/uverbs: Guard legacy bundles without method_elm The legacy write() path dispatches through a uverbs_api_write_method, but the uverbs_attr_bundle passed to provider code does not have an ioctl method element. If malformed provider input causes the common uverbs validation code to emit an error message, uverbs_get_handler_fn() dereferences the uninitialized method_elm pointer. Initialize method_elm explicitly for legacy bundles and make uverbs_get_handler_fn() return NULL when no ioctl method is present. The legacy dispatcher continues to use its local write method, while the ioctl path continues to use the registered ioctl handler.

CVSS Scores

EPSS Scores

Probability:
Percentile:

Meta Information

Published

2026-09-11

Last Modified

2026-09-11

Generated

2026-09-12

AI Q&A

2026-09-12

EPSS Evaluated

N/A

NVD

CVE-2026-89505

EUVD

EUVD-2026-76411

Affected Vendors & Products

Vendor	Product	Version / Range
linux	linux_kernel	*

Helpful Resources

Exploitability

CWE

KEV

CWE ID	Description
CWE-UNKNOWN

Attack-Flow Graph

Executive Summary

This vulnerability in the Linux kernel involves a flaw in the RDMA/uverbs subsystem where a pointer called method_elm is not properly initialized for legacy write operations. When malformed input triggers an error, the code attempts to dereference this uninitialized pointer, potentially causing undefined behavior or crashes.

Detection Guidance

This vulnerability is specific to the Linux kernel's RDMA/uverbs component and requires kernel-level inspection. Detection involves checking kernel logs for errors related to uverbs_attr_bundle or method_elm dereferencing. Use commands like dmesg | grep uverbs or journalctl -k | grep uverbs to search for relevant errors. If you suspect exploitation, monitor for kernel crashes or unexpected behavior in RDMA applications.

Impact Analysis

If exploited, this vulnerability could lead to system instability, crashes, or denial-of-service conditions on affected Linux systems. It may also allow local attackers to escalate privileges or execute arbitrary code, depending on the kernel configuration and environment.

Mitigation Strategies

Immediately update your Linux kernel to the latest stable version that includes the fix for this vulnerability. If updating is not immediately possible, restrict access to RDMA/uverbs functionality by disabling the RDMA subsystem if not required. Monitor vendor advisories for kernel patches and apply them promptly.

Hi! I’m here to help you understand CVE-2026-89505. Ask me anything about the vulnerability, its impact, or mitigation strategies.

0/70