UBUNTU-CVE-2026-72195: High severity ubuntu/linux-hwe-edge vulnerability
In the Linux kernel, the following vulnerability has been resolved: fs/ntfs3: bound attroff in UpdateResidentValue against dataoff In doaction()'s UpdateResidentValue case (fslog.c:3307), lrh->attroff and lrh->redolen come from the on-disk LRH. When they satisfy aoff + dlen < attr->res.dataoff, the assignment attr->res.datasize = cputole32(aoff + dlen - dataoff); underflows to ~4 GiB (e.g. 0xFFFFFFF9 when aoff=0x10, dlen=1, dataoff=0x18). Subsequent code that reads attr->res.datasize to walk the resident attribute payload would then read up to 4 GiB past the 1024-byte MFT record allocation. The existing mienumattr() defense in fs/ntfs3/record.c:287 catches the corrupted datasize on the next attribute walk and fails the mount, but only on the path that walks all attributes. A read site that picks an attribute by name and reads its datasize without re-validating is not covered. Validate aoff against dataoff and asize at the source. Reproduced under UML+KASAN on mainline 8d90b09e6741 via prwarn-only probe: with aoff=0x10 and dataoff=0x18, the post-assignment datasize is 0xfffffff9 (mount then fails at -22 from mienumattr). [almaz.alexandrovich@paragon-software.com: clang-formatted the changes]
Affected Software
Remediation
Recommended actions to resolve this vulnerability, in priority order.
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ubuntu/linux-riscvto a version that resolves this vulnerability.Fixed in 7.0.0-38.38.1 - Compensating control
In fs/ntfs3 fslog.c UpdateResidentValue handling, validate the on-disk aoff against data_off and asize before assigning attr->res.data_size; reject cases where aoff + dlen < attr->res.data_off to prevent the unsigned underflow.
Event History
Frequently Asked Questions
Who is exposed to this issue?
Systems running the listed Ubuntu kernel packages may be exposed when processing a crafted NTFS3 filesystem containing malicious on-disk log record header values. Exploitation requires user interaction, consistent with the supplied vector.
What is the impact of a successful trigger?
Malformed on-disk values can cause a resident attribute data-size calculation to underflow to nearly 4 GiB. Code that reads that size without re-validating it may read far beyond the 1024-byte MFT record allocation, causing an availability impact.
Can existing NTFS3 validation prevent this?
The existing mi_enum_attr() validation can detect the corrupted data size during a full attribute walk and fail the mount with an error. It does not protect read paths that select an attribute by name and use its data size without validating it again.
What should be done if patching cannot happen immediately?
Avoid mounting or otherwise processing untrusted NTFS filesystems with NTFS3 until an updated kernel is deployed. The vulnerable values originate from the filesystem's on-disk log record header.