CVE-2026-80810 io_uring/rsrc: fix folio size overflow in io_vec_fill_bvec()
An integer overflow in Linux kernel io_uring allows local attackers to trigger out-of-bounds writes, potentially leading to privilege escalation or code execution.
- Exploited in the wild
- Not known
- Login needed
- Any signed-in user
- Attackable
- Local or same network only
- Victim action needed
- Not needed
- Fix
- Available
What is CVE-2026-80810?
CVE-2026-80810 is a vulnerability in Linux, published on 4 Sep 2026. It can only be exploited from the same machine or local network, with no action from the victim.
Official description
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.
Which versions are affected by CVE-2026-80810?
How do I fix CVE-2026-80810?
Apply the vendor's patch.
Is CVE-2026-80810 being exploited?
There is no known exploitation of CVE-2026-80810 in the wild and no public exploit code.
Sources
Also known as BELL-CVE-2026-80810, DEBIAN-CVE-2026-80810, GHSA-ccgp-64pj-g833, UBUNTU-CVE-2026-80810.