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CVE-2025-39726 Affecting kernel-modules package, versions *

Severity

 Recommended
low

Based on Red Hat Enterprise Linux security rating.

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  • Snyk IDSNYK-RHEL9-KERNELMODULES-12527979
  • published6 Sept 2025
  • disclosed5 Sept 2025
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Introduced: 5 Sep 2025

NewCVE-2025-39726  (opens in a new tab)

How to fix?

There is no fixed version for RHEL:9 kernel-modules.

NVD Description

Note: Versions mentioned in the description apply only to the upstream kernel-modules package and not the kernel-modules package as distributed by RHEL. See How to fix? for RHEL:9 relevant fixed versions and status.

In the Linux kernel, the following vulnerability has been resolved:

s390/ism: fix concurrency management in ism_cmd()

The s390x ISM device data sheet clearly states that only one request-response sequence is allowable per ISM function at any point in time. Unfortunately as of today the s390/ism driver in Linux does not honor that requirement. This patch aims to rectify that.

This problem was discovered based on Aliaksei's bug report which states that for certain workloads the ISM functions end up entering error state (with PEC 2 as seen from the logs) after a while and as a consequence connections handled by the respective function break, and for future connection requests the ISM device is not considered -- given it is in a dysfunctional state. During further debugging PEC 3A was observed as well.

A kernel message like [ 1211.244319] zpci: 061a:00:00.0: Event 0x2 reports an error for PCI function 0x61a is a reliable indicator of the stated function entering error state with PEC 2. Let me also point out that a kernel message like [ 1211.244325] zpci: 061a:00:00.0: The ism driver bound to the device does not support error recovery is a reliable indicator that the ISM function won't be auto-recovered because the ISM driver currently lacks support for it.

On a technical level, without this synchronization, commands (inputs to the FW) may be partially or fully overwritten (corrupted) by another CPU trying to issue commands on the same function. There is hard evidence that this can lead to DMB token values being used as DMB IOVAs, leading to PEC 2 PCI events indicating invalid DMA. But this is only one of the failure modes imaginable. In theory even completely losing one command and executing another one twice and then trying to interpret the outputs as if the command we intended to execute was actually executed and not the other one is also possible. Frankly, I don't feel confident about providing an exhaustive list of possible consequences.

CVSS Base Scores

version 3.1