CVE-2026-64449 staging: vme_user: bound slave read/write to the kern_buf size
A missing bounds check in the Linux kernel vme_user driver allows out-of-bounds writes, potentially leading to memory corruption and privilege escalation.
- 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-2026-64449?
CVE-2026-64449 is a high-severity memory corruption vulnerability in Linux kernel, published on 25 Jul 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:
staging: vme_user: bound slave read/write to the kern_buf size
The SLAVE-path helpers buffer_to_user() and buffer_from_user() copy 'count' bytes into/out of the fixed-size kern_buf (size_buf == PCI_BUF_SIZE == 0x20000, 128 KiB) using *ppos as the offset, without bounding *ppos + count against size_buf.
vme_user_write()/vme_user_read() only clamp count to the VME window size (image_size = vme_get_size(resource)), which VME_SET_SLAVE sets from the user-supplied slave.size -- validated against the VME address space (up to VME_A32_MAX = 4 GiB), not against PCI_BUF_SIZE. When the window exceeds 128 KiB, a write()/read() copies past the kern_buf allocation.
Clamp count against size_buf in both helpers, with an early return when *ppos is already at/after the buffer end. *ppos is >= 0 here (the caller rejects negative offsets), so size_buf - *ppos cannot wrap. This mirrors the existing clamp in the MASTER-path helpers resource_to_user() / resource_from_user(), and matches the read()/write() convention of a short transfer at end-of-buffer.
Found by static analysis (CodeQL taint tracking + CBMC bounded model checking) and confirmed dynamically under KASAN with the vme_fake bridge:
BUG: KASAN: slab-out-of-bounds in _copy_from_user+0x2d/0x80 Write of size 262144 at addr ffff888004100000 by task trigger/68 _copy_from_user+0x2d/0x80 vme_user_write+0x13e/0x240 [vme_user] vfs_write+0x1b8/0x7a0 ksys_write+0xb8/0x150
Weakness: CWE-787
Which versions are affected by CVE-2026-64449?
It affects 1 product.
Products include Linux kernel.
How do I fix CVE-2026-64449?
Apply the vendor's patch.
Upgrade to the fixed version. Memory-safe languages, compiler hardening and fuzzing prevent most new cases. More about Memory corruption.
Is CVE-2026-64449 being exploited?
There is no known exploitation of CVE-2026-64449 in the wild and no public exploit code.
Other vulnerabilities in Linux kernel
Sources
Also known as BELL-CVE-2026-64449, DEBIAN-CVE-2026-64449, GHSA-fqjm-fj8x-6hp3, ROOT-OS-DEBIAN-12-CVE-2026-64449, ROOT-OS-UBUNTU-2204-CVE-2026-64449, UBUNTU-CVE-2026-64449.