CVE-2026-22980
Unknown Unknown - Not Provided
BaseFortify

Publication date: 2026-01-23

Last updated on: 2026-04-27

Assigner: kernel.org

Description
In the Linux kernel, the following vulnerability has been resolved: nfsd: provide locking for v4_end_grace Writing to v4_end_grace can race with server shutdown and result in memory being accessed after it was freed - reclaim_str_hashtbl in particularly. We cannot hold nfsd_mutex across the nfsd4_end_grace() call as that is held while client_tracking_op->init() is called and that can wait for an upcall to nfsdcltrack which can write to v4_end_grace, resulting in a deadlock. nfsd4_end_grace() is also called by the landromat work queue and this doesn't require locking as server shutdown will stop the work and wait for it before freeing anything that nfsd4_end_grace() might access. However, we must be sure that writing to v4_end_grace doesn't restart the work item after shutdown has already waited for it. For this we add a new flag protected with nn->client_lock. It is set only while it is safe to make client tracking calls, and v4_end_grace only schedules work while the flag is set with the spinlock held. So this patch adds a nfsd_net field "client_tracking_active" which is set as described. Another field "grace_end_forced", is set when v4_end_grace is written. After this is set, and providing client_tracking_active is set, the laundromat is scheduled. This "grace_end_forced" field bypasses other checks for whether the grace period has finished. This resolves a race which can result in use-after-free.
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Meta Information
Published
2026-01-23
Last Modified
2026-04-27
Generated
2026-05-07
AI Q&A
2026-01-23
EPSS Evaluated
2026-05-05
NVD
CVE-2026-22980
EUVD
EUVD-2026-4321
Affected Vendors & Products
Showing 10 associated CPEs
Vendor Product Version / Range
linux linux_kernel From 5.11 (inc) to 5.15.198 (exc)
linux linux_kernel 6.19
linux linux_kernel 6.19
linux linux_kernel 6.19
linux linux_kernel 6.19
linux linux_kernel From 6.13 (inc) to 6.18.6 (exc)
linux linux_kernel From 6.2 (inc) to 6.6.121 (exc)
linux linux_kernel From 6.7 (inc) to 6.12.66 (exc)
linux linux_kernel From 5.16 (inc) to 6.1.161 (exc)
linux linux_kernel From 3.18 (inc) to 5.10.248 (exc)
Helpful Resources
Exploitability
CWE
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KEV
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CWE ID Description
CWE-416 The product reuses or references memory after it has been freed. At some point afterward, the memory may be allocated again and saved in another pointer, while the original pointer references a location somewhere within the new allocation. Any operations using the original pointer are no longer valid because the memory "belongs" to the code that operates on the new pointer.
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AI Powered Q&A
Can you explain this vulnerability to me?

This vulnerability in the Linux kernel involves a race condition when writing to the v4_end_grace variable in the NFS daemon (nfsd). The race occurs during server shutdown, where memory can be accessed after it has been freed, leading to a use-after-free condition. The issue arises because locking cannot be held across the nfsd4_end_grace() call due to potential deadlocks, and the work queue that calls nfsd4_end_grace() during shutdown must be carefully managed to avoid restarting work after shutdown has completed. The patch adds new flags and locking mechanisms to ensure safe client tracking calls and prevent scheduling work after shutdown, thereby resolving the race and use-after-free vulnerability.


How can this vulnerability impact me? :

This vulnerability can lead to a use-after-free condition in the Linux kernel's NFS server component, which may cause system instability, crashes, or potentially allow an attacker to execute arbitrary code or cause denial of service by exploiting the race condition during server shutdown.


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