Freed-memory read via post-shutdown state-table walk
Published Sep 11, 2026 · Updated Sep 11, 2026
Use-after-free in Linux NFSD 7.0 allows local users with CAP_SYS_ADMIN to trigger a freed-memory read through unlock_filesystem. The handler calls nfsd4_cancel_copy_by_sb() before taking nfsd_mutex or confirming nfsd_serv, so it walks a freed conf_id_hashtbl after shutdown. Exploitation requires stopping NFSD and writing a filesystem path to the administrative procfs interface; the observed result is a slab-use-after-free read.
Summary
What happened
Use-after-free in Linux NFSD 7.0 allows local users with CAP_SYS_ADMIN to trigger a freed-memory read through unlock_filesystem. The handler calls nfsd4_cancel_copy_by_sb() before taking nfsd_mutex or confirming nfsd_serv, so it walks a freed conf_id_hashtbl after shutdown. Exploitation requires stopping NFSD and writing a filesystem path to the administrative procfs interface; the observed result is a slab-use-after-free read.
The record
- CVE
- CVE-2026-89661
- Published
- Sep 11, 2026
- Updated
- Sep 11, 2026
- Vendor
- The Linux Kernel Organization
- Product
- Linux
- Classifications
- Unavailable
- Attack vector
- local
- Privileges
- admin
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?
Compare these published version ranges with your installed build and any vendor patches.
- Affected versionversion=3daab3112f039cf849f96764019b096bb0a39d04 <0c1a755b7212e0835398d4df5e782ea85ccd7476
- Affected versionversion=3daab3112f039cf849f96764019b096bb0a39d04 <292d915d3ba6fd15eeb88351fa10581683073109
- Affected versionversion=7.0
What conditions does exploitation require?
What is affected?
Published CVSS scores
No CVSS assessment is available in this record.
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Attacks
What attackers are doing with it
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Weakness, pattern, technique
No sourced classifications are available.
Public exploit references
- Upstream unlock_filesystem trigger descriptionproof of concept · demonstrated
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Technologies
Your stack
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Your stack
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