CVE-2026-64567
btrfs: reject free space cache with more entries than pages
Description
In the Linux kernel, the following vulnerability has been resolved: btrfs: reject free space cache with more entries than pages When loading a v1 free space cache, __load_free_space_cache() takes num_entries and num_bitmaps straight from the on-disk btrfs_free_space_header. That header is stored in the tree_root under a key with type 0, which the tree-checker has no case for, so neither count is validated before the load trusts it. The load loops num_entries times and maps the next page whenever the current one runs out, going through io_ctl_check_crc() -> io_ctl_map_page(), which does io_ctl->pages[io_ctl->index++]. But pages[] is allocated in io_ctl_init() from the cache inode's i_size, not from num_entries: num_pages = DIV_ROUND_UP(i_size_read(inode), PAGE_SIZE); io_ctl->pages = kcalloc(num_pages, sizeof(struct page *), GFP_NOFS); So if num_entries claims more records than the pages can hold, io_ctl->index runs off the end of pages[]. The write side never hits this because io_ctl_add_entry() and io_ctl_add_bitmap() both stop once io_ctl->index >= io_ctl->num_pages; the read side just never had the same check. To trigger it, take a clean cache (num_entries = <N> here), set num_entries in the header to 0x10000, and fix up the leaf checksum so it still passes the tree-checker. The cache inode has i_size = 65536, so num_pages is 16 and pages[] is a 16-pointer (kmalloc-128) array. The load now tries to read 65536 entries, io_ctl->index walks up to 16, and pages[16] is read past the array: BUG: KASAN: slab-out-of-bounds in io_ctl_check_crc (fs/btrfs/free-space-cache.c:420 fs/btrfs/free-space-cache.c:565) Read of size 8 at addr ffff88800c833a80 by task kworker/u8:3/58 io_ctl_check_crc (fs/btrfs/free-space-cache.c:420 fs/btrfs/free-space-cache.c:565) __load_free_space_cache (fs/btrfs/free-space-cache.c:655 fs/btrfs/free-space-cache.c:820) load_free_space_cache (fs/btrfs/free-space-cache.c:1017) caching_thread (fs/btrfs/block-group.c:880) btrfs_work_helper (fs/btrfs/async-thread.c:312) process_one_work worker_thread kthread ret_from_fork free-space-cache.c:420 is io_ctl_map_page(), inlined into io_ctl_check_crc() at line 565, which is why that is the frame KASAN names. The out-of-bounds slot is then treated as a struct page and handed to crc32c(), so the bad read turns into a GP fault. Add the missing check to io_ctl_check_crc(), which is where both the entry loop and the bitmap loop end up. When num_entries is too large the load now fails like any corrupt cache: __load_free_space_cache() drops it and rebuilds the free space from the extent tree, so a valid cache is never rejected.
INFO
Published Date :
Aug. 5, 2026, 8:16 a.m.
Last Modified :
Aug. 5, 2026, 8:16 a.m.
Remotely Exploit :
No
Source :
416baaa9-dc9f-4396-8d5f-8c081fb06d67
Affected Products
The following products are affected by CVE-2026-64567
vulnerability.
Even if cvefeed.io is aware of the exact versions of the
products
that
are
affected, the information is not represented in the table below.
No affected product recoded yet
Solution
- Apply the kernel patch to validate free space cache entries.
- Update the Linux kernel to the patched version.
- Rebuild the free space cache if corrupted.
- Monitor system logs for related errors.
References to Advisories, Solutions, and Tools
Here, you will find a curated list of external links that provide in-depth
information, practical solutions, and valuable tools related to
CVE-2026-64567.
CWE - Common Weakness Enumeration
While CVE identifies
specific instances of vulnerabilities, CWE categorizes the common flaws or
weaknesses that can lead to vulnerabilities. CVE-2026-64567 is
associated with the following CWEs:
Common Attack Pattern Enumeration and Classification (CAPEC)
Common Attack Pattern Enumeration and Classification
(CAPEC)
stores attack patterns, which are descriptions of the common attributes and
approaches employed by adversaries to exploit the CVE-2026-64567
weaknesses.
We scan GitHub repositories to detect new proof-of-concept exploits. Following list is a collection of public exploits and proof-of-concepts, which have been published on GitHub (sorted by the most recently updated).
Results are limited to the first 15 repositories due to potential performance issues.
The following list is the news that have been mention
CVE-2026-64567 vulnerability anywhere in the article.
The following table lists the changes that have been made to the
CVE-2026-64567 vulnerability over time.
Vulnerability history details can be useful for understanding the evolution of a vulnerability, and for identifying the most recent changes that may impact the vulnerability's severity, exploitability, or other characteristics.
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New CVE Received by 416baaa9-dc9f-4396-8d5f-8c081fb06d67
Aug. 05, 2026
Action Type Old Value New Value Added Affected [{'repo': 'https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git', 'vendor': 'Linux', 'product': 'Linux', 'versions': [{'status': 'affected', 'version': '5b0e95bf607ddd59b39f52d3d55e6581c817b530', 'lessThan': '33878ba25e2638bc0c61623d7a05c9ca2b74c039', 'versionType': 'git'}, {'status': 'affected', 'version': '5b0e95bf607ddd59b39f52d3d55e6581c817b530', 'lessThan': '404a0b986e0b6e79738fdf1f0ebbbc43b9acd2a2', 'versionType': 'git'}, {'status': 'affected', 'version': '5b0e95bf607ddd59b39f52d3d55e6581c817b530', 'lessThan': '5e1b2ca6b34939e70fb0785e8222b53cf060016f', 'versionType': 'git'}, {'status': 'affected', 'version': '5b0e95bf607ddd59b39f52d3d55e6581c817b530', 'lessThan': 'f9fef131fa3f59b857217f522fa5ea430d1b707c', 'versionType': 'git'}, {'status': 'affected', 'version': '5b0e95bf607ddd59b39f52d3d55e6581c817b530', 'lessThan': 'a2d8d5647ed854e38f941741aea45b9eb15a6350', 'versionType': 'git'}], 'programFiles': ['fs/btrfs/free-space-cache.c'], 'defaultStatus': 'unaffected'}, {'repo': 'https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git', 'vendor': 'Linux', 'product': 'Linux', 'versions': [{'status': 'affected', 'version': '3.2'}, {'status': 'unaffected', 'version': '0', 'lessThan': '3.2', 'versionType': 'semver'}, {'status': 'unaffected', 'version': '6.6.148', 'versionType': 'semver', 'lessThanOrEqual': '6.6.*'}, {'status': 'unaffected', 'version': '6.12.101', 'versionType': 'semver', 'lessThanOrEqual': '6.12.*'}, {'status': 'unaffected', 'version': '6.18.42', 'versionType': 'semver', 'lessThanOrEqual': '6.18.*'}, {'status': 'unaffected', 'version': '7.1.6', 'versionType': 'semver', 'lessThanOrEqual': '7.1.*'}, {'status': 'unaffected', 'version': '7.2-rc4', 'versionType': 'original_commit_for_fix', 'lessThanOrEqual': '*'}], 'programFiles': ['fs/btrfs/free-space-cache.c'], 'defaultStatus': 'affected'}] Added Description In the Linux kernel, the following vulnerability has been resolved: btrfs: reject free space cache with more entries than pages When loading a v1 free space cache, __load_free_space_cache() takes num_entries and num_bitmaps straight from the on-disk btrfs_free_space_header. That header is stored in the tree_root under a key with type 0, which the tree-checker has no case for, so neither count is validated before the load trusts it. The load loops num_entries times and maps the next page whenever the current one runs out, going through io_ctl_check_crc() -> io_ctl_map_page(), which does io_ctl->pages[io_ctl->index++]. But pages[] is allocated in io_ctl_init() from the cache inode's i_size, not from num_entries: num_pages = DIV_ROUND_UP(i_size_read(inode), PAGE_SIZE); io_ctl->pages = kcalloc(num_pages, sizeof(struct page *), GFP_NOFS); So if num_entries claims more records than the pages can hold, io_ctl->index runs off the end of pages[]. The write side never hits this because io_ctl_add_entry() and io_ctl_add_bitmap() both stop once io_ctl->index >= io_ctl->num_pages; the read side just never had the same check. To trigger it, take a clean cache (num_entries = <N> here), set num_entries in the header to 0x10000, and fix up the leaf checksum so it still passes the tree-checker. The cache inode has i_size = 65536, so num_pages is 16 and pages[] is a 16-pointer (kmalloc-128) array. The load now tries to read 65536 entries, io_ctl->index walks up to 16, and pages[16] is read past the array: BUG: KASAN: slab-out-of-bounds in io_ctl_check_crc (fs/btrfs/free-space-cache.c:420 fs/btrfs/free-space-cache.c:565) Read of size 8 at addr ffff88800c833a80 by task kworker/u8:3/58 io_ctl_check_crc (fs/btrfs/free-space-cache.c:420 fs/btrfs/free-space-cache.c:565) __load_free_space_cache (fs/btrfs/free-space-cache.c:655 fs/btrfs/free-space-cache.c:820) load_free_space_cache (fs/btrfs/free-space-cache.c:1017) caching_thread (fs/btrfs/block-group.c:880) btrfs_work_helper (fs/btrfs/async-thread.c:312) process_one_work worker_thread kthread ret_from_fork free-space-cache.c:420 is io_ctl_map_page(), inlined into io_ctl_check_crc() at line 565, which is why that is the frame KASAN names. The out-of-bounds slot is then treated as a struct page and handed to crc32c(), so the bad read turns into a GP fault. Add the missing check to io_ctl_check_crc(), which is where both the entry loop and the bitmap loop end up. When num_entries is too large the load now fails like any corrupt cache: __load_free_space_cache() drops it and rebuilds the free space from the extent tree, so a valid cache is never rejected. Added Reference https://git.kernel.org/stable/c/33878ba25e2638bc0c61623d7a05c9ca2b74c039 Added Reference https://git.kernel.org/stable/c/404a0b986e0b6e79738fdf1f0ebbbc43b9acd2a2 Added Reference https://git.kernel.org/stable/c/5e1b2ca6b34939e70fb0785e8222b53cf060016f Added Reference https://git.kernel.org/stable/c/a2d8d5647ed854e38f941741aea45b9eb15a6350 Added Reference https://git.kernel.org/stable/c/f9fef131fa3f59b857217f522fa5ea430d1b707c