CVE-2025-39939: linux kernel Memory Corruption — Fix

Description

In the Linux kernel, the following vulnerability has been resolved: iommu/s390: Fix memory corruption when using identity domain zpci_get_iommu_ctrs() returns counter information to be reported as part of device statistics; these counters are stored as part of the s390_domain. The problem, however, is that the identity domain is not backed by an s390_domain and so the conversion via to_s390_domain() yields a bad address that is zero'd initially and read on-demand later via a sysfs read. These counters aren't necessary for the identity domain; just return NULL in this case. This issue was discovered via KASAN with reports that look like: BUG: KASAN: global-out-of-bounds in zpci_fmb_enable_device when using the identity domain for a device on s390.

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CVSS v3.1 Score

7.8

HIGH

CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H

Weakness Type (CWE)

CWE-787 Out-of-bounds Write

Affected Products

Vendor	Product	Versions
linux	linux_kernel	6.15 — 6.16.9
linux	linux_kernel	All
linux	linux_kernel	All
linux	linux_kernel	All
linux	linux_kernel	All
linux	linux_kernel	All
linux	linux_kernel	All

References

Advisories & Patches

https://git.kernel.org/stable/c/17a58caf3863163c4a84a218a9649be2c8061443 https://git.kernel.org/stable/c/b3506e9bcc777ed6af2ab631c86a9990ed97b474

Frequently Asked Questions

What is CVE-2025-39939? +

In the Linux kernel, the following vulnerability has been resolved: iommu/s390: Fix memory corruption when using identity domain zpci_get_iommu_ctrs() returns counter information to be reported as part of device statistics; these counters are stored as part of the s390_domain. The problem, however, is that the identity domain is not backed by an s390_domain and so the conversion via to_s390_domain() yields a bad address that is zero'd initially and read on-demand later via a sysfs read. These counters aren't necessary for the identity domain; just return NULL in this case. This issue was discovered via KASAN with reports that look like: BUG: KASAN: global-out-of-bounds in zpci_fmb_enable_device when using the identity domain for a device on s390. It has a CVSS v3.1 base score of 7.8 (HIGH).

How severe is CVE-2025-39939? +

CVE-2025-39939 has a CVSS v3.1 score of 7.8 out of 10, rated HIGH. This is a high-severity vulnerability that should be prioritized for patching.

What products are affected by CVE-2025-39939? +

CVE-2025-39939 affects products from linux, specifically: linux_kernel. Check the affected products table above for specific version ranges.

How do I check if I'm vulnerable to CVE-2025-39939? +

You can use Secably's free Website Scanner to check your website for known vulnerabilities. For infrastructure scanning, use the Port Scanner to identify exposed services that may be affected. Check the vendor advisories linked above for specific patch and version information.

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