CVE-2026-99180: In the Linux kernel, the following vulnerability has been resolved: unicode: free the map after a grace period generic_ci_d_hash() and generic_ci_d

In the Linux kernel, the following vulnerability has been resolved: unicode: free the map after a grace period generic_ci_d_hash() and generic_ci_d_compare()

In the Linux kernel, the following vulnerability has been resolved: unicode: free the map after a grace period generic_ci_d_hash() and generic_ci_d_compare() read sb->s_encoding and dereference the unicode map while a pathwalk in rcu mode holds nothing but rcu_read_lock(). The filesystems that use them, ext4, f2fs and tmpfs, drop the map with utf8_unload() from ->put_super(), which runs when the last reference to the mount goes away. A lookup that is still inside such a filesystem at that point reads a freed map. With a pathwalk held up in utf8_casefold_hash() while the last reference to a casefolded tmpfs goes away: BUG: KASAN: slab-use-after-free in utf8nlookup+0x74c/0x950 Read of size 8 at addr ff110001030fe658 by task walker/98 Call Trace: <TASK> utf8nlookup+0x74c/0x950 utf8byte+0x160/0x1560 utf8_casefold_hash+0x167/0x230 generic_ci_d_hash+0xdd/0x1c0 link_path_walk+0x11ad/0x1d30 path_lookupat+0x63/0xb00 filename_lookup+0x1f1/0x5b0 vfs_statx+0xd7/0x3b0 [...] Allocated by task 94: __kmalloc_cache_noprof+0x249/0x560 utf8_load+0x4e/0x570 shmem_parse_opt_casefold.isra.0+0x92/0x270 [...] Freed by task 97: kfree+0x1db/0x5b0 s

Description from the National Vulnerability Database, published by 416baaa9-dc9f-4396-8d5f-8c081fb06d67

What it means for a small business

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Sources

Part of the Huttenlocher Technologies vulnerability database, refreshed twice a day from CISA and the NVD. The title, category and plain-language guidance are ours; check the linked record before acting on a detail. This is general guidance, not a review of your systems.

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