CVE-2026-89778

/// Technical 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

/// Remediation

Check the references section for vendor advisories, patches, and mitigation guidance. If immediate patching is not possible, review the CVSS vector to understand the attack surface and apply compensating controls such as network segmentation or access restrictions.

/// References