Medium [CVE-2026-89678] NFS daemon (nfsd) data corruption due to incorrect partial-write detection
This medium-severity Red Hat Linux advisory covers CVE-2026-89678.
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Summary
A flaw was found in the Linux kernel's Network File System (NFS) daemon (nfsd) component. The `nfsd_direct_write()` function, responsible for handling direct writes, incorrectly detects partial writes.
This issue occurs because the logic for detecting short writes compares the actual bytes written against a residual count rather than the original requested length.
As a result, partial writes between 50% and 99% of the intended size are not properly identified, leading to subsequent data being written at incorrect file offsets and the NFS client receiving an inaccurate report of bytes written. This can allow a remote attacker to cause data corruption on the NFS server.
Red Hat severity: Important — CVSS 6.8 (CVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:U/C:N/I:H/A:H). Weakness: CWE-823.
Affected versions
No affected-version range was extracted from the source record. The vendor advisory is authoritative — check it before change work.
Official advisory · medium-confidence parse· fetched 2 hours ago·verify at source
Fixed versions
No fixed release is recorded yet. That does not prove no patch exists — confirm against the vendor advisory.
Official advisory · medium-confidence parse· fetched 2 hours ago·verify at source
Mitigation
The source record does not include mitigation steps. That is not a statement that no fix exists — read the vendor advisory below for the authoritative guidance.
Official advisory · medium-confidence parse· fetched 2 hours ago·verify at source
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