Silent data loss via raced writeback cursor
Published Sep 11, 2026 · Updated Sep 11, 2026
Race condition in Linux kernel nfsd allows remote attackers to cause silent data loss through asynchronous NFSv4 COPY. The _nfsd_copy_file_range() path samples dst->f_wb_err after its copy loop, so a concurrent COMMIT or stable WRITE can advance the shared cursor first and suppress filemap_check_wb_err(). The gate requires access to an NFSv4 export, concurrent operations on the destination inode, and a writeback failure; the server then falsely reports FILE_SYNC4 durability.
Summary
What happened
Race condition in Linux kernel nfsd allows remote attackers to cause silent data loss through asynchronous NFSv4 COPY. The _nfsd_copy_file_range() path samples dst->f_wb_err after its copy loop, so a concurrent COMMIT or stable WRITE can advance the shared cursor first and suppress filemap_check_wb_err(). The gate requires access to an NFSv4 export, concurrent operations on the destination inode, and a writeback failure; the server then falsely reports FILE_SYNC4 durability.
The record
- CVE
- CVE-2026-89704
- Published
- Sep 11, 2026
- Updated
- Sep 11, 2026
- Vendor
- The Linux Kernel Organization
- Product
- Linux
- Classifications
- T1485
- Attack vector
- network
- Privileges
- Unavailable
Timeline
How it unfolded
- Sep 11, 2026CVE publishedPublication date reported by the CVE source.
- Sep 11, 2026Record updatedLatest update available in the CVE record.
Exploitability
Present is not the same as exploitable
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Is a vulnerable build present?
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- Affected versionversion=3145fe0ebb16e1715ad541a301bc6675c8375fcd
- Affected versionversion=5.10.124 <5.11
- Affected versionversion=5.15.49 <5.16
- Affected versionversion=5.17
- Affected versionversion=555dbf1a9aac6d3150c8b52fa35f768a692f4eeb <20a67a7d18221af736f124770c2c5e859b479046
- Affected versionversion=555dbf1a9aac6d3150c8b52fa35f768a692f4eeb <52b2db7a72e19ac2686fa4b2a52406661e7bf9e2
- Affected versionversion=555dbf1a9aac6d3150c8b52fa35f768a692f4eeb <8277d4a11ae2cb5495842be558fd946032c24363
- Affected versionversion=555dbf1a9aac6d3150c8b52fa35f768a692f4eeb <a1cbafe756cd5e6ab0e099062f37da7a5b081169
- Affected versionversion=f14816f2f928c560d28ba344af689f56efcd6f55
What conditions does exploitation require?
What is affected?
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Attacks
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Weakness, pattern, technique
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Technologies
Your stack
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Your stack
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