# CVE-2026-31651: Linux Kernel NULL pointer dereference in vub300 MMC driver

Source: https://junglewise.ai/threats/cve-2026-31651-linux-kernel-null-pointer-dereference-in-vub300-mmc-driver  
Publisher: Junglewise Threat Intelligence, https://junglewise.ai/threats  
Published: 2026-04-24. Updated: 2026-07-14  
License: CC BY 4.0 with a link back

CVE-2026-31651 · Severity: medium · CVSS 5.5 · Published 2026-04-24

A vulnerability in the Linux kernel's VUB300 USB-to-SD driver can cause a system crash when a device is disconnected. This affects systems using specific SD/MMC hardware interfaces, including certain industrial Siemens controllers. An attacker with local access could exploit this to cause a denial-of-service, potentially disrupting operations or industrial processes.

Technologies: [Linux Kernel](https://junglewise.ai/threats/technologies/kernel), [Siemens SIMATIC S7-1500 CPU 1518-4 PN/DP MFP](https://junglewise.ai/threats/technologies/simatic-s7-1500-cpu-1518-4-pn-dp-mfp). Vendors: [Linux](https://junglewise.ai/threats/vendors/linux), [Siemens](https://junglewise.ai/threats/vendors/siemens).

## Quick answers

**Is CVE-2026-31651 exploited in the wild?** No. Junglewise Threat Intelligence has no report of CVE-2026-31651 being exploited in the wild.

**How severe is CVE-2026-31651?** Medium severity, with a CVSS score of 5.5, published 24 April 2026.

**Which products and versions are affected?** Linux Kernel 3.0 to 6.14; Siemens SIMATIC S7-1500 CPU 1518-4 PN/DP MFP V3.1.5, V3.1.6.

**Is there a fix for CVE-2026-31651?** No fixed version is recorded yet. Check the vendor's advisory in the references below. If you run it, Junglewise drafts a mitigation that fits your setup and applies it once you approve, with senior security engineers behind it.

**How is CVE-2026-31651 attacked?** It is attacked with local access, in an operating system.

**Am I affected by CVE-2026-31651?** Check whether you run Linux Kernel or Siemens SIMATIC S7-1500 CPU 1518-4 PN/DP MFP 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

A race condition or improper cleanup sequence exists in the vub300_disconnect function within drivers/mmc/host/vub300.c. The driver was dropping its reference to driver data (kref_put) before deregistering the MMC host (mmc_remove_host), leading to a NULL pointer dereference or use-after-free if the host was accessed during the teardown process. A local attacker can trigger this by initiating a device disconnect, resulting in a kernel oops and denial of service. Patches have been backported to multiple stable kernel branches (3.0+).

## Affected products

- Linux Linux Kernel 3.0 to 6.14
- Siemens SIMATIC S7-1500 CPU 1518-4 PN/DP MFP V3.1.5, V3.1.6

## Timeline

- 2026-03-27: other: Patch authored by Johan Hovold
- 2026-04-24: disclosed: CVE published

## References

- [https://git.kernel.org/stable/c/517b58e1d067115f80d198feee10192da4c424d0](https://git.kernel.org/stable/c/517b58e1d067115f80d198feee10192da4c424d0)
- [https://git.kernel.org/stable/c/53f2642d77ab5f1f303388bff5500363c6cf962c](https://git.kernel.org/stable/c/53f2642d77ab5f1f303388bff5500363c6cf962c)
- [https://git.kernel.org/stable/c/6446516e626ce7c44bdadbcbb3d7677a2c52ce93](https://git.kernel.org/stable/c/6446516e626ce7c44bdadbcbb3d7677a2c52ce93)
- [https://git.kernel.org/stable/c/6468cab1173f44f7a4b7a05ce8abfdfd1ce1557a](https://git.kernel.org/stable/c/6468cab1173f44f7a4b7a05ce8abfdfd1ce1557a)
- [https://git.kernel.org/stable/c/8d09e75759cb2afc0732acfb5a14a93c03805a61](https://git.kernel.org/stable/c/8d09e75759cb2afc0732acfb5a14a93c03805a61)
- [https://git.kernel.org/stable/c/ba3b9429de94958dc0060d9816a915dd75c34919](https://git.kernel.org/stable/c/ba3b9429de94958dc0060d9816a915dd75c34919)
- [https://git.kernel.org/stable/c/c83a282615d8f7ba28cebddd54600b419d562d82](https://git.kernel.org/stable/c/c83a282615d8f7ba28cebddd54600b419d562d82)

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