CVE-2026-72196 fs/ntfs3: bound copy_lcns dp->page_lcns[] index in analysis pass
A missing bounds check in the Linux kernel NTFS3 driver allows out-of-bounds writes during log replay, potentially leading to memory corruption or system crashes.
- Exploited in the wild
- Not known
- Login needed
- Not needed
- Attackable
- Local or same network only
- Victim action needed
- Not needed
- Fix
- Available
What is CVE-2026-72196?
CVE-2026-72196 is a high-severity memory corruption vulnerability in Linux, published on 15 Aug 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:
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]
Which versions are affected by CVE-2026-72196?
How do I fix CVE-2026-72196?
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-2026-72196 being exploited?
There is no known exploitation of CVE-2026-72196 in the wild and no public exploit code.
Sources
Also known as BELL-CVE-2026-72196, DEBIAN-CVE-2026-72196, GHSA-7v7p-59m6-6h9x, UBUNTU-CVE-2026-72196.