Bug 2536373 (CVE-2026-90118)

Summary: CVE-2026-90118 kernel: ntfs: fix off-by-one page overflow in ntfs_decompress()
Product: [Other] Security Response Reporter: OSIDB Bzimport <bzimport>
Component: vulnerabilityAssignee: Product Security DevOps Team <prodsec-dev>
Status: NEW --- QA Contact:
Severity: medium Docs Contact:
Priority: medium    
Version: unspecifiedCC: akhatavk, aos-team-art-private, asdas, dpaolell, jdelft, jupierce, lgarciaa, mbiarnes, ppalepu, ppostler, prdhamdh, rhel-process-autobot, sghai, sidsharm, suppawar, vlaad, watson-tool-maintainers
Target Milestone: ---Keywords: Security
Target Release: ---   
Hardware: All   
OS: Linux   
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Fixed In Version: Doc Type: ---
Doc Text:
A flaw was found in the Linux kernel's NTFS filesystem driver. An off-by-one error in the `ntfs_decompress()` function, when processing a specially crafted compressed data attribute, can lead to out-of-bounds writes. This could result in memory corruption, potentially allowing a local attacker to escalate privileges or cause a denial of service.
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oVirt Team: --- RHEL 7.3 requirements from Atomic Host:
Cloudforms Team: --- Target Upstream Version:
Embargoed:

Description OSIDB Bzimport 2026-09-17 17:35:16 UTC
In the Linux kernel, the following vulnerability has been resolved:

ntfs: fix off-by-one page overflow in ntfs_decompress()

The per-token range check in ntfs_decompress() uses

	if (cb >= cb_sb_end || dp_addr > dp_sb_end)
		break;

so dp_addr == dp_sb_end falls through to the symbol copy
`*dp_addr++ = *cb++`, writing one byte past the destination page.  Since
NTFS_SB_SIZE == PAGE_SIZE the destination is a single page, so the byte
lands in the adjacent page, and *dest_ofs is left one past the sub-block
end (the later `*dest_ofs &= ~PAGE_MASK` then yields 1, not 0, so the page
is never finalized and later sub-blocks keep writing further past it).  A
corrupted compressed $DATA attribute thus produces a bounded run of
out-of-bounds writes when the file is read.

Break as soon as dp_addr reaches dp_sb_end; a full sub-block still
completes, as its final copy advances dp_addr to exactly dp_sb_end.