CVE-2026-89778 is a vulnerability in Linux Kernel
Published on September 16, 2026
isofs: fix out-of-bounds page array access on empty zisofs block
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
Products Associated with CVE-2026-89778
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Affected Versions
Linux:- Version 59bc055211b8d266ab6089158058bf8268e02006 and below 8b994ac5778a725982fd6a8a3afcaa068d4a93e3 is affected.
- Version 59bc055211b8d266ab6089158058bf8268e02006 and below ad3249cdf9d4ba34bb8b1ff3956a4020fdfb5b0a is affected.
- Version 59bc055211b8d266ab6089158058bf8268e02006 and below 85904076cece72ee3194646ad7ac8e6659d999aa is affected.
- Version 59bc055211b8d266ab6089158058bf8268e02006 and below f03425dcbe04aec3c27b9917e97d7d23a2908dda is affected.
- Version 59bc055211b8d266ab6089158058bf8268e02006 and below cd616aa0449a772a6956abf03358f0ff31720580 is affected.
- Version 59bc055211b8d266ab6089158058bf8268e02006 and below 9c6eace8d07e90f038c89eb3b756d65a7e259d48 is affected.
- Version 59bc055211b8d266ab6089158058bf8268e02006 and below 68d4d3e78150c7ed7d1195af63ad1e6ace30c661 is affected.
- Version 2.6.33 is affected.
- Before 2.6.33 is unaffected.
- Version 5.15.221, <= 5.15.* is unaffected.
- Version 6.1.188, <= 6.1.* is unaffected.
- Version 6.6.157, <= 6.6.* is unaffected.
- Version 6.12.110, <= 6.12.* is unaffected.
- Version 6.18.52, <= 6.18.* is unaffected.
- Version 7.2.6, <= 7.2.* is unaffected.
- Version 7.3-rc1, <= * is unaffected.