Linux kernel Btrfs btrfs_ioctl_space_info() TOCTOU information 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 block group RAID type lists. In the first pass, the function counts entries to determine the allocation size for the userspace-visible buffer; in the second pass, it fills that buffer. Because the groups_sem rwlock is released between the two passes, concurrent block group removal can reduce the number of entries present during the second pass. If fewer entries are filled than were counted initially, copy_to_user() may copy the full alloc_size, including trailing uninitialized kmalloc heap bytes, to userspace. The upstream fix changes the code to copy only the actually populated total_spaces entries from the second pass and replaces kmalloc with kzalloc to reduce the risk of future heap-data disclosure from copy-size mismatches.
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Impact
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Mitigation
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Remediation
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Exploits
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No public exploit code observed for this vulnerability.
Affected products & vendors
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Recent activity
12 sources tracked across advisories, community write-ups, and news. New activity surfaces here as Mallory finds it.
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.
The version that knows your environment.
Query your assets running an affected version, and investigate the blast radius.
Every observed campaign linking this CVE to a named adversary.
Malware families riding this exploit, with evidence and IOCs.
YARA, Sigma, Snort, and vendor rules, auto-deployed to your SIEM.
Cross-references every affected SKU, including bundled OEM variants.
Community discussion across Reddit, Mastodon, and other social sources.