CVE-2026-52959
HighCVSS 7.8Exploitation Probability (EPSS)
Low risk1th percentile — higher than 1% of all known CVEs
Summary
In the Linux kernel's sev-guest driver, a vulnerability was found where a host-controlled value is used to compute the page order when freeing a buffer. The host may return an expected buffer size, which is then used to calculate the page order, potentially leading to corruption in the page allocator.
Risk Assessment
A malicious host in a virtualized environment could exploit this vulnerability to cause kernel memory corruption, potentially leading to system crashes or privilege escalation within the guest.
Recommendation
Immediately update the Linux kernel to a version containing the fix, which uses alloc_pages_exact() and free_pages_exact() instead of computing the page order from host-controlled values.
Original NVD description (English source)
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.