Linux Kernel up to 6.15.6/6.16-rc5 try_to_unmap_one out-of-bounds

Summaryinfo

A vulnerability was found in Linux Kernel up to 6.15.6/6.16-rc5 and classified as problematic. This affects the function try_to_unmap_one. The manipulation results in out-of-bounds. This vulnerability was named CVE-2025-38447. There is no available exploit. It is suggested to upgrade the affected component.

Detailsinfo

A vulnerability, which was classified as problematic, was found in Linux Kernel up to 6.15.6/6.16-rc5. Affected is the function try_to_unmap_one. The manipulation with an unknown input leads to a out-of-bounds vulnerability. CWE is classifying the issue as CWE-125. The product reads data past the end, or before the beginning, of the intended buffer. This is going to have an impact on confidentiality. CVE summarizes:

In the Linux kernel, the following vulnerability has been resolved: mm/rmap: fix potential out-of-bounds page table access during batched unmap As pointed out by David[1], the batched unmap logic in try_to_unmap_one() may read past the end of a PTE table when a large folio's PTE mappings are not fully contained within a single page table. While this scenario might be rare, an issue triggerable from userspace must be fixed regardless of its likelihood. This patch fixes the out-of-bounds access by refactoring the logic into a new helper, folio_unmap_pte_batch(). The new helper correctly calculates the safe batch size by capping the scan at both the VMA and PMD boundaries. To simplify the code, it also supports partial batching (i.e., any number of pages from 1 up to the calculated safe maximum), as there is no strong reason to special-case for fully mapped folios.

The advisory is shared for download at git.kernel.org. This vulnerability is traded as CVE-2025-38447 since 04/16/2025. There are known technical details, but no exploit is available.

Upgrading to version 6.15.7 or 6.16-rc6 eliminates this vulnerability. Applying the patch 510fe9c15d07e765d96be9a9dc37e5057c6c09f4/ddd05742b45b083975a0855ef6ebbf88cf1f532a 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 vulnerability database at CERT Bund (WID-SEC-2025-1653). Once again VulDB remains the best source for vulnerability data.

Affected

• Debian Linux
• Amazon Linux 2
• Red Hat Enterprise Linux
• Ubuntu Linux
• SUSE Linux
• Oracle Linux
• IBM QRadar SIEM
• SUSE openSUSE
• RESF Rocky Linux
• Dell Avamar
• Open Source Linux Kernel
• Dell NetWorker
• Dell Secure Connect Gateway

Productinfo

Type

• Operating System

Vendor

• Linux

Name

• Kernel

Version

• 6.15.0
• 6.15.1
• 6.15.2
• 6.15.3
• 6.15.4
• 6.15.5
• 6.15.6
• 6.16-rc1
• 6.16-rc2
• 6.16-rc3
• 6.16-rc4
• 6.16-rc5

License

• open-source

Website

• Vendor: https://www.kernel.org/

CPE 2.3info

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CPE 2.2info

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Entryinfo

Once again VulDB remains the best source for vulnerability data.

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