# CVE-2026-90173: Linux kernel smbdirect use-after-free in completion queue cleanup

Source: https://junglewise.ai/threats/cve-2026-90173-linux-kernel-smbdirect-use-after-free-in-completion-queue-cleanup  
Publisher: Junglewise Threat Intelligence, https://junglewise.ai/threats  
Published: 2026-09-17. Updated: 2026-09-26  
License: CC BY 4.0 with a link back

CVE-2026-90173 · Severity: critical · CVSS 9.8 · Published 2026-09-17

The Linux kernel's SMB Direct protocol handler contains a use-after-free vulnerability in its completion queue cleanup code. When tearing down network connections, freed completion queues can be accessed by pending asynchronous work, leading to memory corruption and kernel crashes. An attacker with network access to trigger SMB Direct connections could exploit this to cause denial of service or potentially gain code execution.

Technologies: [Linux Kernel](https://junglewise.ai/threats/technologies/kernel). Vendors: [Linux](https://junglewise.ai/threats/vendors/linux).

## Quick answers

**Is CVE-2026-90173 exploited in the wild?** No. Junglewise Threat Intelligence has no report of CVE-2026-90173 being exploited in the wild.

**How severe is CVE-2026-90173?** Critical severity, with a CVSS score of 9.8, published 17 September 2026.

**Which products and versions are affected?** Linux Kernel 7.2.0 (and likely earlier versions with smbdirect support).

**Is there a fix for CVE-2026-90173?** A patch was published on 2026: Fix applied in kernel commit resolving smbdirect completion queue teardown Junglewise finds every place you run it, drafts the upgrade and applies it once you approve.

**How is CVE-2026-90173 attacked?** It is attacked over the network, in an operating system.

**Am I affected by CVE-2026-90173?** Check whether you run Linux Kernel at an affected version. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.

## Technical details

The vulnerability is a use-after-free in the smbdirect subsystem's queue pair destruction code. The function smbdirect_connection_destroy_qp() creates send and receive completion queues using ib_alloc_cq_any() with IB_POLL_WORKQUEUE mode, which registers an internal completion handler (ib_cq_poll_work) on a workqueue. However, teardown uses ib_destroy_cq() instead of ib_free_cq(), which frees the CQ structure without cancelling the poll work handler. If a completion arrives after the CQ is freed—particularly from Soft-RoCE (rxe) posting late RNR errors—the handler attempts to re-queue work on the already-freed CQ, causing a use-after-free fault. The fix replaces ib_destroy_cq() with ib_free_cq(), which properly synchronizes and cancels the poll work before freeing the queue structure. Network reachability to trigger SMB Direct connections is the primary attack precondition.

## Affected products

- Linux Linux kernel 7.2.0 (and likely earlier versions with smbdirect support)

## Timeline

- 2026-09-17: disclosed
- 2026: patched: Fix applied in kernel commit resolving smbdirect completion queue teardown

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