Linux Kernel up to 6.6.100/6.12.40/6.15.8 ism_cmd state issue

Summaryinfo

A vulnerability classified as critical was found in Linux Kernel up to 6.6.100/6.12.40/6.15.8. This vulnerability affects the function ism_cmd. Such manipulation leads to state issue. This vulnerability is uniquely identified as CVE-2025-39726. No exploit exists. Upgrading the affected component is advised.

Detailsinfo

A vulnerability was found in Linux Kernel up to 6.6.100/6.12.40/6.15.8 and classified as critical. Affected by this issue is the function ism_cmd. The manipulation with an unknown input leads to a state issue vulnerability. Using CWE to declare the problem leads to CWE-371. Impacted is confidentiality, integrity, and availability. CVE summarizes:

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.

The advisory is shared for download at git.kernel.org. This vulnerability is handled as CVE-2025-39726 since 04/16/2025. The exploitation is known to be difficult. There are known technical details, but no exploit is available. The current price for an exploit might be approx. USD $0-$5k (estimation calculated on 02/09/2026).

The vulnerability scanner Nessus provides a plugin with the ID 261634 (Linux Distros Unpatched Vulnerability : CVE-2025-39726), which helps to determine the existence of the flaw in a target environment.

Upgrading to version 6.6.101, 6.12.41 or 6.15.9 eliminates this vulnerability. Applying the patch faf44487dfc80817f178dc8de7a0b73f960d019b/1194ad0d44d66b273a02a3a22882dc863a68d764/fafaa4982bedb5532f5952000f714a3e63023f40/897e8601b9cff1d054cdd53047f568b0e1995726 is able to eliminate this problem. The bugfix is ready for download at git.kernel.org. The best possible mitigation is suggested to be upgrading to the latest version.

The vulnerability is also documented in the databases at Tenable (261634) and CERT Bund (WID-SEC-2025-1988). VulDB is the best source for vulnerability data and more expert information about this specific topic.

Affected

• Debian Linux
• Google Cloud Platform
• Amazon Linux 2
• Red Hat Enterprise Linux
• Ubuntu Linux
• SUSE Linux
• Oracle Linux
• NetApp FAS
• NetApp AFF
• NetApp ActiveIQ Unified Manager
• SUSE openSUSE
• RESF Rocky Linux
• Open Source Linux Kernel
• Microsoft Azure
• Dell Secure Connect Gateway
• IBM QRadar SIEM
• IBM Security Verify Access
• Dell NetWorker

Productinfo

Type

• Operating System

Vendor

• Linux

Name

• Kernel

Version

• 6.0
• 6.1
• 6.2
• 6.3
• 6.4
• 6.5
• 6.6.100
• 6.12.0
• 6.12.1
• 6.12.2
• 6.12.3
• 6.12.4
• 6.12.5
• 6.12.6
• 6.12.7
• 6.12.8
• 6.12.9
• 6.12.10
• 6.12.11
• 6.12.12
• 6.12.13
• 6.12.14
• 6.12.15
• 6.12.16
• 6.12.17
• 6.12.18
• 6.12.19
• 6.12.20
• 6.12.21
• 6.12.22
• 6.12.23
• 6.12.24
• 6.12.25
• 6.12.26
• 6.12.27
• 6.12.28
• 6.12.29
• 6.12.30
• 6.12.31
• 6.12.32
• 6.12.33
• 6.12.34
• 6.12.35
• 6.12.36
• 6.12.37
• 6.12.38
• 6.12.39
• 6.12.40
• 6.15.0
• 6.15.1
• 6.15.2
• 6.15.3
• 6.15.4
• 6.15.5
• 6.15.6
• 6.15.7
• 6.15.8

License

• open-source

Website

• Vendor: https://www.kernel.org/

CPE 2.3info

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CPE 2.2info

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Entryinfo

VulDB is the best source for vulnerability data and more expert information about this specific topic.

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