btrfs: lzo: reject inline extents without valid headers
CVE-2026-74723 · published 22 Aug 2026
How serious is it
- Severity: critical, CVSS score 9.8 out of 10.
- No exploit prediction (EPSS) score yet.
- Not on the CISA list of exploited vulnerabilities.
- No public exploit in Exploit-DB.
Is your app affected by CVE-2026-74723?
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Who is affected
- Linux Linux: a6fa6fae40ec336c7df6155255ae64ebef43a8bc to < 5d00c9c1c951ae82d498eabbdfff973252a05c50, a6fa6fae40ec336c7df6155255ae64ebef43a8bc to < fd150d7c8e0ad9d721c011cfd4cc0f3c65bd6834, a6fa6fae40ec336c7df6155255ae64ebef43a8bc to < 056876c9db1e969bfcf7d8583c7696cc0dd080df, a6fa6fae40ec336c7df6155255ae64ebef43a8bc to < fc50b475ad27f50b4dcc98fc4c44e8802bc1b248
- Linux Linux: 2.6.38
How to check
- Find out whether you run the affected product and which version, then compare it with the versions above.
How to fix
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- Apply the vendor's update or mitigation from the references below. If there is none yet, limit exposure of the affected service until there is.
- If a vulnerable version was live, check your logs and rotate the secrets that server could read.
The advisory
In the Linux kernel, the following vulnerability has been resolved:
btrfs: lzo: reject inline extents without valid headers
[BUG]
For a crafted btrfs image, the following KASAN can be triggered when
reading an inline lzo compressed file extent:
BUG: KASAN: slab-out-of-bounds in lzo_decompress+0x57d/0x700
Read of size 4 at addr ffff888006f2e644 by task btrfs_lzo_inlin/77
Call Trace:
<TASK>
dump_stack_lvl+0x5b/0x70
print_report+0xd1/0x610
kasan_report+0xe0/0x110
__asan_report_load_n_noabort+0x13/0x20
lzo_decompress+0x57d/0x700
btrfs_decompress+0x140/0x1c0
uncompress_inline+0x147/0x1b0
btrfs_get_extent+0xb23/0x10a0
btrfs_do_readpage.constprop.0+0x538/0x1ac0
btrfs_readahead+0x32f/0x5f0
read_pages+0x16f/0x850
page_cache_ra_unbounded+0x296/0x490
do_page_cache_ra+0xd9/0x130
page_cache_sync_ra+0x3ee/0x6f0
filemap_get_pages+0x306/0x15c0
filemap_read+0x329/0xd00
btrfs_file_read_iter+0x1f8/0x2b0
vfs_read+0x4ef/0x720
ksys_read+0xf8/0x1d0
__x64_sys_read+0x71/0xb0
x64_sys_call+0x1ab0/0x1b70
do_syscall_64+0x61/0x470
entry_SYSCALL_64_after_hwframe+0x4b/0x53
</TASK>
[CAUSE]
For an inline lzo compressed file extent, there should always be one lzo
header, recording the total length of the compressed data, followed by
one segment header, recording the compressed lzo payload.
But if a crafted inline lzo compressed file extent contains only an lzo
header, without the segment header or payload, lzo_decompress() will
still try to read the segment header, causing a read beyond the item
boundary.
Furthermore if the inline lzo compressed file extent is the first item
of the leaf, it will be at the extent buffer boundary. The above
out-of-boundary read will go beyond the extent buffer boundary,
triggering the above KASAN report.
[FIX]
Validate the total length of the inlined lzo compressed file extent, to
make sure there is at least one LZO header and one segment header, and a
non-zero payload.
[ Rework the commit message to remove slop ]
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References
- git.kernel.org/stable/c/5d00c9c1c951ae82d498eabbdfff973252a05c50
- git.kernel.org/stable/c/fd150d7c8e0ad9d721c011cfd4cc0f3c65bd6834
- git.kernel.org/stable/c/056876c9db1e969bfcf7d8583c7696cc0dd080df
- git.kernel.org/stable/c/fc50b475ad27f50b4dcc98fc4c44e8802bc1b248
- git.kernel.org/stable/c/0fa78ef637deb5dbe341582f88553a4bce496de0
Merged from CVE List. Last updated 25 Oct 2026. All vulnerabilities · RSS · JSON