CVE-2026-64533 fs/ntfs3: validate lcns_follow in log_replay conversion
A malformed NTFS filesystem image can trigger an out-of-bounds memory write in the Linux kernel NTFS3 driver, potentially leading to code execution or system crash.
- Exploited in the wild
- Not known
- Login needed
- Not needed
- Attackable
- Local or same network only
- Victim action needed
- A user has to click or open something
- Fix
- Available
What is CVE-2026-64533?
CVE-2026-64533 is a high-severity memory corruption vulnerability in Linux, published on 27 Jul 2026. It can only be exploited from the same machine or local network, and only if a user opens a file or follows a link.
Official description
In the Linux kernel, the following vulnerability has been resolved:
fs/ntfs3: validate lcns_follow in log_replay conversion
log_replay() converts DIR_PAGE_ENTRY_32 records into DIR_PAGE_ENTRY records when replaying version 0 restart tables.
During this conversion, the memmove() length is derived directly from the on-disk lcns_follow field:
memmove(&dp->vcn, &dp0->vcn_low, 2 * sizeof(u64) + le32_to_cpu(dp->lcns_follow) * sizeof(u64));
check_rstbl() validates restart table structure, but does not constrain per-entry lcns_follow values relative to the entry size. A malformed filesystem image can provide an oversized lcns_follow value, causing the conversion memmove() to access memory beyond the bounds of the allocated restart table buffer.
The same field is later used to bound iteration over page_lcns[], so validating lcns_follow during conversion also prevents downstream out-of-bounds access from the same malformed metadata.
Compute the maximum valid lcns_follow from the already-validated restart table entry size and reject entries that exceed this bound. Reuse the existing t16/t32 scratch variables already declared in log_replay() to avoid introducing new declarations.
[[email protected]: fixed the conflicts]
Weakness: CWE-787
Which versions are affected by CVE-2026-64533?
How do I fix CVE-2026-64533?
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-2026-64533 being exploited?
There is no known exploitation of CVE-2026-64533 in the wild and no public exploit code.
Sources
Also known as AZL-93962, BELL-CVE-2026-64533, DEBIAN-CVE-2026-64533, GHSA-hvv2-rwwx-6q3h, ROOT-OS-DEBIAN-12-CVE-2026-64533, UBUNTU-CVE-2026-64533.