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VulnerabilityPublished Updated

CVE-2026-64567: Linux kernel · Out-of-bounds Read

Affects Linux kernelSource CVE Database V5

0

Not known to be exploited · CVSS 7.8 High · fixed in f9fef131fa3f59b857217f522fa5ea430d1b707c : patch Linux kernel soon.

Data as of 26 Oct 2026, 17:30 UTC

CVSS 3.1 base score
7.8High
How severe the flaw is on the 0–10 CVSS scale.
EPSS
0.1% chance of exploitation in 30 days – higher than 2% of CVEsExploit Prediction Scoring System: the likelihood attackers will use this flaw soon.
CISA SSVC
Exploitation
No evidence of active exploitation and no public proof of concept
Automatable
Attackers cannot reliably automate steps 1–4 of the kill chain
Technical impact
Total control over the software or total information disclosure

CISA SSVC assessment, 2026-10-16.

Patch
Available – fixed in f9fef131fa3f59b857217f522fa5ea430d1b707c, c9c38066b6446e83668c041702bb639b0ca49363, a2d8d5647ed854e38f941741aea45b9eb15a6350 +5
CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H

Exploitation evidence

  1. Disclosed: evidence found.

    CVE published 5 Aug 2026

  2. Detectable: no evidence on record.

    No public nuclei template indexed

  3. Weaponised: no evidence on record.

    No public exploit code indexed in Metasploit or Exploit-DB

  4. Exploited in the wild: no evidence on record.

    Not in CISA KEV and no source reports exploitation

  5. Observed by OffSeq Mirage: no evidence on record.

    No attack traffic recorded by OffSeq Mirage sensors

A missing step is not evidence of safety. Sources: cve.org (opens in a new tab), the Metasploit, Exploit-DB and nuclei-templates index as of 26 Oct 2026.

What to do

Upgrade to a fixed release listed under Affected software.

Affected software

ProductAffectedFixed in
LinuxLinuxAffected
  • ≥ 5b0e95bf607ddd59b39f52d3d55e6581c817b530, < f9fef131fa3f59b857217f522fa5ea430d1b707c
Fixed in
  • f9fef131fa3f59b857217f522fa5ea430d1b707c
LinuxLinuxAffected
  • ≥ 5b0e95bf607ddd59b39f52d3d55e6581c817b530, < c9c38066b6446e83668c041702bb639b0ca49363
Fixed in
  • c9c38066b6446e83668c041702bb639b0ca49363
LinuxLinuxAffected
  • ≥ 5b0e95bf607ddd59b39f52d3d55e6581c817b530, < a2d8d5647ed854e38f941741aea45b9eb15a6350
Fixed in
  • a2d8d5647ed854e38f941741aea45b9eb15a6350
LinuxLinuxAffected
  • ≥ 5b0e95bf607ddd59b39f52d3d55e6581c817b530, < 094734c7aaa2b36751dc32480a680a4952685e78
Fixed in
  • 094734c7aaa2b36751dc32480a680a4952685e78
LinuxLinuxAffected
  • ≥ 5b0e95bf607ddd59b39f52d3d55e6581c817b530, < 33878ba25e2638bc0c61623d7a05c9ca2b74c039
Fixed in
  • 33878ba25e2638bc0c61623d7a05c9ca2b74c039
LinuxLinuxAffected
  • ≥ 5b0e95bf607ddd59b39f52d3d55e6581c817b530, < 404a0b986e0b6e79738fdf1f0ebbbc43b9acd2a2
Fixed in
  • 404a0b986e0b6e79738fdf1f0ebbbc43b9acd2a2

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.

References

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