Linux kernel Btrfs btrfs_ioctl_space_info() TOCTOU info leak
CVE-2026-46159 is a Linux kernel vulnerability in the Btrfs filesystem, specifically in btrfs_ioctl_space_info(). The flaw is a time-of-check/time-of-use race between two passes over the block-group RAID type lists. In the first pass, the function counts entries to determine the allocation size for the userspace result buffer. The groups_sem rwlock is then released before a second pass populates the buffer. If block groups are concurrently removed between the two passes, the second pass may fill fewer entries than were counted initially. The vulnerable code could still call copy_to_user() with the original alloc_size, causing trailing uninitialized kmalloc heap bytes to be copied to userspace. The upstream fix changes the copy logic to use only total_spaces, the actual number of entries filled during the second pass, and replaces kmalloc with kzalloc to reduce the risk of future heap disclosure from copy-size mismatches.
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Mitigation
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Exploits
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Recent activity
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Linux kernel vulnerability in SCTP SENDALL list cursor revalidation.
A Linux kernel Btrfs information disclosure vulnerability caused by a TOCTOU race in btrfs_ioctl_space_info(), where concurrent block group removal can cause copy_to_user() to copy uninitialized heap memory to userspace.
A Linux kernel Btrfs vulnerability involving a TOCTOU issue in btrfs_ioctl_space_info() that can lead to information disclosure.
Linux kernel time-of-check/time-of-use vulnerability in btrfs_ioctl_space_info() that can lead to information disclosure.
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Every observed campaign linking this CVE to a named adversary.
Malware families riding this exploit, with evidence and IOCs.
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Cross-references every affected SKU, including bundled OEM variants.
Community discussion across Reddit, Mastodon, and other social sources.