CVE-2026-80810
UnknownSummary
In the Linux kernel's io_uring/rsrc subsystem, a vulnerability was found in io_vec_fill_bvec() due to an integer overflow when calculating folio size. Using a plain int instead of unsigned long for bit shifting leads to undefined behavior for folio shifts of 32 or more, causing out-of-bounds writes. The issue mainly affects systems with gigantic hugetlb pages (e.g., 16G on arm64).
Risk Assessment
The vulnerability can lead to kernel memory corruption, potentially causing system crashes or privilege escalation. Organizations using io_uring with large hugetlb pages on 64-bit architectures are at risk of system instability.
Recommendation
Apply the official Linux kernel patch that changes the shift to 1UL immediately. Update the system to a patched kernel version and monitor distribution security advisories.
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Original NVD description (English source)
In the Linux kernel, the following vulnerability has been resolved: io_uring/rsrc: fix folio size overflow in io_vec_fill_bvec() io_vec_fill_bvec() computes the folio size with a plain int 1: unsigned long folio_size = 1 << imu->folio_shift; imu->folio_shift is unsigned int and comes from folio_shift() of the folio backing the registered buffer, so it can be 32 or more on a 64 bit kernel. Shifting int 1 that far is undefined, and on x86 and arm64 the count is taken modulo 32, so a shift of 34 yields 4 rather than 16G. Every other folio_shift shift in this file already uses 1UL. The result is that the segment estimate and the fill loop disagree. io_estimate_bvec_size() sizes the bvec array with the real shift: max_segs += (iov[i].iov_len >> shift) + 2; so a 1M iovec on a 16G folio is charged 2 segments, while io_vec_fill_bvec() then walks the same iovec in folio_size chunks of 4 bytes and writes res_bvec[bvec_idx] a quarter of a million times, past the end of the array it was given. src_bvec is advanced once per iteration as well, so imu->bvec is read past its end at the same time. validate_fixed_range() only checks that the range is inside the registered buffer and does not bound the segment count. Reaching it needs a folio with a shift of at least 32, which means a gigantic hugetlb page: 16G on arm64 with 64K pages, where CONT_PMD_SHIFT is 34 and hugetlb_add_hstate(CONT_PMD_SHIFT - PAGE_SHIFT) registers that size, and likewise on powerpc. x86_64 tops out at 1G, so a shift of 30, which still fits in int and is unaffected. Use 1UL, as the rest of the file does.
Vulnerability data from NVD (NIST) · CISA KEV · EPSS