Is CVE-2025-39857 exploited in the wild?

No. Junglewise Threat Intelligence has no report of CVE-2025-39857 being exploited in the wild.

How severe is CVE-2025-39857?

High severity, with a CVSS score of 7.5, published 19 September 2025.

Which products and versions are affected?

Linux Kernel 6.0 to 6.1.151, 6.2 to 6.6.105, 6.7 to 6.12.46, 6.13 to 6.16.6, 6.17-rc1 to 6.17-rc4, 6.0 to 6.1.151, 6.6.105, 6.12.46, 6.16.6; Siemens SIMATIC CN 4100 before V5.0.

Is there a fix for CVE-2025-39857?

A patch was published on 2025-08-28: Initial patch authored by Liu Jian Junglewise finds every place you run it, drafts the upgrade and applies it once you approve.

How is CVE-2025-39857 attacked?

It is attacked over the network or with local access, in an operating system.

Am I affected by CVE-2025-39857?

Check whether you run Linux Kernel or Siemens SIMATIC CN 4100 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-2025-39857: Linux Kernel NULL pointer dereference in net/smc

CVE-2025-39857 · Severity: high · CVSS 7.5 · Published 2025-09-19

A vulnerability exists in the Linux kernel's Shared Memory Communications (SMC) protocol, which is used for high-performance data exchange. When using specific software-based network acceleration (RoCE), the system may encounter a critical error and crash. This can lead to a complete denial of service, impacting the availability of applications and services relying on these network protocols.

Technologies: Linux Kernel, Siemens SIMATIC CN 4100. Vendors: Linux, Siemens.

Quick answers

Is CVE-2025-39857 exploited in the wild?: No. Junglewise Threat Intelligence has no report of CVE-2025-39857 being exploited in the wild.
How severe is CVE-2025-39857?: High severity, with a CVSS score of 7.5, published 19 September 2025.
Which products and versions are affected?: Linux Kernel 6.0 to 6.1.151, 6.2 to 6.6.105, 6.7 to 6.12.46, 6.13 to 6.16.6, 6.17-rc1 to 6.17-rc4, 6.0 to 6.1.151, 6.6.105, 6.12.46, 6.16.6; Siemens SIMATIC CN 4100 before V5.0.
Is there a fix for CVE-2025-39857?: A patch was published on 2025-08-28: Initial patch authored by Liu Jian Junglewise finds every place you run it, drafts the upgrade and applies it once you approve.
How is CVE-2025-39857 attacked?: It is attacked over the network or with local access, in an operating system.
Am I affected by CVE-2025-39857?: Check whether you run Linux Kernel or Siemens SIMATIC CN 4100 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 NULL pointer dereference vulnerability exists in the 'smc_ib_is_sg_need_sync()' function within the 'net/smc' subsystem of the Linux kernel. The issue occurs because the code fails to validate the 'ibdev->dma_device' pointer when a software RDMA over Converged Ethernet (RoCE) device is used. An attacker or specific network conditions triggering 'smc_listen_work' can cause a kernel panic (Oops), leading to a denial of service. The fix introduces a null pointer check for 'dma_device' before it is accessed. Patches have been released for multiple stable kernel branches including 6.1.y, 6.6.y, 6.12.y, and 6.16.y.

Affected products

Linux Linux Kernel 6.0 to 6.1.151, 6.6.105, 6.12.46, 6.16.6
Siemens SIMATIC CN 4100 before V5.0

Timeline

2025-08-28: patched: Initial patch authored by Liu Jian
2025-09-19: disclosed: CVE published

References

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