OCTOBER 7, 2026
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Case File

CVE-2026-89778

CRITICAL · CVSS 9.8 EPSS 0.70% Public Exploit

Source: NVD + CISA KEV + EPSS · Published 2026-09-16 · Last synced 2026-10-07

CyberRota Analysis

AI-Generated

The vulnerability affects the Linux kernel's handling of zisofs compressed files, specifically in the zisofs_uncompress_block() function, which can lead to an out-of-bounds access when processing empty blocks. This flaw allows an attacker to exploit crafted ISO9660 images, potentially leading to unauthorized memory access and system instability. Organizations using affected Linux distributions or F5 products should prioritize remediation to mitigate the risk of exploitation.

Public Exploit Signal

A public exploit, PoC, GitHub repository or Metasploit reference was detected for this CVE.

Detected Signals
exploit

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CVE
CVE-2026-89778
Severity
CRITICAL
CVSS
9.8
EPSS
0.70%
Linux F5

Original NVD 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