CVE-2026-89778
Received
Received - Intake
Out-of-Bounds Page Access in Linux Kernel ISOFS Zisofs
Vulnerability report for CVE-2026-89778, including description, CVSS score, EPSS score, affected products, exploitability, helpful resources, and attack-flow context.
Publication date: 2026-09-16
Last updated on: 2026-09-16
Assigner: kernel.org
Description
Description
In the Linux kernel, the following vulnerability has been resolved:
isofs: fix out-of-bounds page array access on empty zisofs block
zisofs_uncompress_block()'s empty-block fast path returns
pcount << PAGE_SHIFT, ignoring the incoming poffset, unlike the
decompression path which returns bytes produced relative to poffset.
zisofs_fill_pages() uses that return to advance its page cursor, so when
the zisofs block size is below PAGE_SIZE and a sub-page block leaves
poffset partway into a page, a following empty block over-counts and
advances pages[] one element past its end, after which
"if (poffset && *pages)" reads pages[1] out of bounds. rock.c only
rejects a block-size shift > 17, so a crafted "ZF" Rock Ridge record can
set it below PAGE_SHIFT; the bug is reached by an ordinary read() of a
compressed file on such a mounted ISO9660 image.
Return the byte count relative to poffset and zero only
[poffset, PAGE_SIZE) of the first page, matching the decompression path.
The page-aligned case (poffset == 0) is unaffected.
BUG: KASAN: slab-out-of-bounds in zisofs_read_folio (fs/isofs/compress.c:290)
Read of size 8 at addr ffff88800f5eac48 by task exploit/142
zisofs_read_folio (fs/isofs/compress.c:290)
read_pages (mm/readahead.c:184)
...
filemap_read (mm/filemap.c:2814)
vfs_read (fs/read_write.c:574)
__x64_sys_pread64 (fs/read_write.c:769)
do_syscall_64 (arch/x86/entry/syscall_64.c:94)
entry_SYSCALL_64_after_hwframe (arch/x86/entry/entry_64.S:121)
The buggy address is located 0 bytes to the right of the
allocated 8-byte region in the kmalloc-8 cache
CVSS Scores
EPSS Scores
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Meta Information
Affected Vendors & Products
| Vendor | Product | Version / Range |
|---|---|---|
| linux | linux_kernel | * |
Helpful Resources
Exploitability
CWE
KEV
| CWE ID | Description |
|---|---|
| CWE-UNKNOWN |
