Is CVE-2026-31649 exploited in the wild?

No. Junglewise Threat Intelligence has no report of CVE-2026-31649 being exploited in the wild.

How severe is CVE-2026-31649?

Critical severity, with a CVSS score of 9.8, published 24 April 2026.

Which products and versions are affected?

Siemens SIMATIC S7-1500 CPU 1518-4 PN/DP MFP V3.1.5, V3.1.6.

Is there a fix for CVE-2026-31649?

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-2026-31649 attacked?

It is attacked over the network, in an operating system.

Am I affected by CVE-2026-31649?

Check whether you run 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.

CVE-2026-31649: Linux Kernel stmmac integer underflow in jumbo_frm

CVE-2026-31649 · Severity: critical · CVSS 9.8 · Published 2026-04-24

A vulnerability exists in the Linux kernel's stmmac network driver, which is commonly used in embedded systems and industrial controllers like Siemens SIMATIC S7-1500. An attacker could send specially crafted network packets to trigger a system crash or gain unauthorized access to sensitive information stored in the device's memory. This could lead to operational downtime or the theft of proprietary data in industrial environments.

Technologies: Siemens SIMATIC S7-1500 CPU 1518-4 PN/DP MFP. Vendors: Siemens.

Quick answers

Is CVE-2026-31649 exploited in the wild?: No. Junglewise Threat Intelligence has no report of CVE-2026-31649 being exploited in the wild.
How severe is CVE-2026-31649?: Critical severity, with a CVSS score of 9.8, published 24 April 2026.
Which products and versions are affected?: Siemens SIMATIC S7-1500 CPU 1518-4 PN/DP MFP V3.1.5, V3.1.6.
Is there a fix for CVE-2026-31649?: 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-2026-31649 attacked?: It is attacked over the network, in an operating system.
Am I affected by CVE-2026-31649?: Check whether you run 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

An integer underflow vulnerability exists in the jumbo_frm() function within the stmmac driver's chain-mode implementation. The root cause is an unconditional subtraction where the linear buffer length (nopaged_len) is subtracted from the maximum buffer size (bmax) without verifying that nopaged_len is larger. When a packet has a small linear portion but large page fragments, this results in a massive unsigned integer value for the remaining length. This causes a loop to execute excessively, mapping arbitrary kernel memory to the DMA engine via dma_map_single(). On systems without an IOMMU, this allows for kernel memory disclosure and potential hardware-driven memory corruption. The fix involves clamping the buffer length to the minimum of the linear portion and the maximum buffer size.

Affected products

Linux Linux Kernel Fixed in versions 10d12b92, 275bdf76, 2c91b399, 513e0673, 51f4e090, 6fca757c, a2b68a9a, b7b80121
Siemens SIMATIC S7-1500 CPU 1518-4 PN/DP MFP V3.1.5, V3.1.6

Timeline

2026-03-31: other: Vulnerability fixed in kernel source by Tyllis Xu
2026-04-24: disclosed: CVE published

References

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