CVE-2025-39939
CVE-2025-39939 is a high-severity vulnerability in Linux Linux Kernel with a CVSS 3.x base score of 7.8. It is not currently listed as actively exploited by CISA, and its EPSS exploit-prediction score is low. The underlying weakness is classified as CWE-787.
Key facts
- Severity: High (CVSS 3.x base score 7.8)
- EPSS exploit prediction: 0% (3rd percentile)
- Actively exploited: Not listed in CISA KEV
- EU (EUVD) id: EUVD-2025-32386
- Weakness: CWE-787
- Affected product: Linux Linux Kernel
- Published:
- Last modified:
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.
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.
- How severe is CVE-2025-39939?
- CVE-2025-39939 has a CVSS 3.x base score of 7.8, rated high severity. It is exploitable over local access with low attack complexity, requires low privileges and no user interaction. Impact on confidentiality is high, integrity high, and availability high.
- Is CVE-2025-39939 being actively exploited?
- It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 0% (3rd percentile), an estimate of the probability of exploitation in the next 30 days.
- What products are affected by CVE-2025-39939?
- CVE-2025-39939 primarily affects Linux Linux Kernel. In total, 7 product configurations (CPEs) are listed as vulnerable; see the affected-products list for the exact versions.
- How do I fix CVE-2025-39939?
- Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround. Given its high severity, prioritise patching exposed systems.
- Does CVE-2025-39939 have an EU (EUVD) identifier?
- Yes. CVE-2025-39939 is tracked in the ENISA EU Vulnerability Database (EUVD) as EUVD-2025-32386.
- When was CVE-2025-39939 published?
- CVE-2025-39939 was published on 2025-10-04 and last updated on 2026-06-17.
References
- https://git.kernel.org/stable/c/17a58caf3863163c4a84a218a9649be2c8061443
- https://git.kernel.org/stable/c/b3506e9bcc777ed6af2ab631c86a9990ed97b474
Affected products (7)
- cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*
- cpe:2.3:o:linux:linux_kernel:6.17:rc1:*:*:*:*:*:*
- cpe:2.3:o:linux:linux_kernel:6.17:rc2:*:*:*:*:*:*
- cpe:2.3:o:linux:linux_kernel:6.17:rc3:*:*:*:*:*:*
- cpe:2.3:o:linux:linux_kernel:6.17:rc4:*:*:*:*:*:*
- cpe:2.3:o:linux:linux_kernel:6.17:rc5:*:*:*:*:*:*
- cpe:2.3:o:linux:linux_kernel:6.17:rc6:*:*:*:*:*:*
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