CVE-2026-52959: virt: sev-guest: Do not use host-controlled page order in cleanup path

Severity: high (CVSS 7.8 v3.1)
Exploited in the wild: not listed in CISA KEV
EPSS: 0.1% probability of exploitation in the next 30 days
Public exploit or detection template: none known
Published: 2026-06-24 · updated 2026-07-14

Description

In the Linux kernel, the following vulnerability has been resolved: virt: sev-guest: Do not use host-controlled page order in cleanup path When issuing an extended guest request (SVM_VMGEXIT_EXT_GUEST_REQUEST), get_ext_report() allocates a buffer to retrieve a certificate blob from the host, keeping track of its size in report_req->certs_len. However, the host may return SNP_GUEST_VMM_ERR_INVALID_LEN, indicating an invalid buffer size, as well as the expected length of such buffer. get_ext_report() subsequently updates report_req->certs_len with the host-controlled value, and cleans up the buffer by computing a page order from such value. This is incorrect, as the host-provided length may not match the page order of the original allocation, potentially resulting in corruption in the page allocator. Fix this by using alloc_pages_exact() instead, and reusing @npages to compute the size passed to free_pages_exact(). For consistency, also use @npages to compute the size when allocating the pages, even though this last change has no functional effect.

Affected products

Linux kernel: from 6.13.8 before 6.14; from 6.14.1 before 6.18.33; from 6.19 before 7.0.10; 6.14, 6.14-rc6, 6.14-rc7, 7.1-rc1, 7.1-rc2, 7.1-rc3 — fixed in 6.14, 6.18.33, 7.0.10

How to fix

Upgrade to a fixed version: Linux kernel 6.14, 6.18.33, 7.0.10. Check the vendor advisory for mitigations.

References

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