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CVE-2025-39836: efi: stmm: Fix incorrect buffer allocation method

• Severity: high (CVSS 7.8 v3.1)
• Exploited in the wild: not listed in CISA KEV
• EPSS: 0.2% probability of exploitation in the next 30 days
• Public exploit or detection template: none known
• Published: 2025-09-16 · updated 2026-10-19
• Weakness: CWE-787

Description

In the Linux kernel, the following vulnerability has been resolved: efi: stmm: Fix incorrect buffer allocation method The communication buffer allocated by setup_mm_hdr() is later on passed to tee_shm_register_kernel_buf(). The latter expects those buffers to be contiguous pages, but setup_mm_hdr() just uses kmalloc(). That can cause various corruptions or BUGs, specifically since commit 9aec2fb0fd5e ("slab: allocate frozen pages"), though it was broken before as well. Fix this by using alloc_pages_exact() instead of kmalloc().

Affected products

• Linux kernel: from 6.8 before 6.12.45; from 6.13 before 6.16.5; 6.17-rc1, 6.17-rc2, 6.17-rc3 — fixed in 6.12.45, 6.16.5

How to fix

Upgrade to a fixed version: Linux kernel 6.12.45, 6.16.5. Check the vendor advisory for mitigations.

References

• https://git.kernel.org/stable/c/630c0e6064daf84f17aad1a7d9ca76b562e3fe47
• https://git.kernel.org/stable/c/77ff27ff0e4529a003c8a1c2492c111968c378d3
• https://git.kernel.org/stable/c/c5e81e672699e0c5557b2b755cc8f7a69aa92bff

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