{"id":"CVE-2026-89778","title":"In the Linux kernel, the following vulnerability has been resolved:\n\nisofs: fix out-of-bounds page array access on empty zisofs block\n\nzisofs_uncompress_block()'s empty-block fast path returns\npcount << PAGE_SHIFT, ignoring the incoming …","summary":"In the Linux kernel, the following vulnerability has been resolved:\n\nisofs: fix out-of-bounds page array access on empty zisofs block\n\nzisofs_uncompress_block()'s empty-block fast path returns\npcount << PAGE_SHIFT, ignoring the incoming …","severity":"critical","cvss":9.8,"cvssVector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H","vendor":"Linux","product":"Linux","affected":["Linux >= 59bc055211b8d266ab6089158058bf8268e02006 < 8b994ac5778a725982fd6a8a3afcaa068d4a93e3","Linux >= 59bc055211b8d266ab6089158058bf8268e02006 < ad3249cdf9d4ba34bb8b1ff3956a4020fdfb5b0a","Linux >= 59bc055211b8d266ab6089158058bf8268e02006 < 85904076cece72ee3194646ad7ac8e6659d999aa","Linux >= 59bc055211b8d266ab6089158058bf8268e02006 < f03425dcbe04aec3c27b9917e97d7d23a2908dda","Linux >= 59bc055211b8d266ab6089158058bf8268e02006 < cd616aa0449a772a6956abf03358f0ff31720580","Linux >= 59bc055211b8d266ab6089158058bf8268e02006 < 9c6eace8d07e90f038c89eb3b756d65a7e259d48","Linux >= 59bc055211b8d266ab6089158058bf8268e02006 < 68d4d3e78150c7ed7d1195af63ad1e6ace30c661","Linux 2.6.33"],"published":"2026-09-16","updated":"2026-09-16","sourceUpdated":"2026-09-16T15:18:07.167","source":"NVD","sourceUrl":"https://nvd.nist.gov/vuln/detail/CVE-2026-89778","references":[{"url":"https://git.kernel.org/stable/c/68d4d3e78150c7ed7d1195af63ad1e6ace30c661","label":"416baaa9-dc9f-4396-8d5f-8c081fb06d67"},{"url":"https://git.kernel.org/stable/c/85904076cece72ee3194646ad7ac8e6659d999aa","label":"416baaa9-dc9f-4396-8d5f-8c081fb06d67"},{"url":"https://git.kernel.org/stable/c/8b994ac5778a725982fd6a8a3afcaa068d4a93e3","label":"416baaa9-dc9f-4396-8d5f-8c081fb06d67"},{"url":"https://git.kernel.org/stable/c/9c6eace8d07e90f038c89eb3b756d65a7e259d48","label":"416baaa9-dc9f-4396-8d5f-8c081fb06d67"},{"url":"https://git.kernel.org/stable/c/ad3249cdf9d4ba34bb8b1ff3956a4020fdfb5b0a","label":"416baaa9-dc9f-4396-8d5f-8c081fb06d67"},{"url":"https://git.kernel.org/stable/c/cd616aa0449a772a6956abf03358f0ff31720580","label":"416baaa9-dc9f-4396-8d5f-8c081fb06d67"},{"url":"https://git.kernel.org/stable/c/f03425dcbe04aec3c27b9917e97d7d23a2908dda","label":"416baaa9-dc9f-4396-8d5f-8c081fb06d67"}],"tags":["nvd","cve.org"],"ingestedAt":"2026-09-16T08:52:29.594Z","epss":0.00688,"epssPercentile":0.51285,"slug":"CVE-2026-89778","body":"## Overview\n\nIn the Linux kernel, the following vulnerability has been resolved:\n\nisofs: fix out-of-bounds page array access on empty zisofs block\n\nzisofs_uncompress_block()'s empty-block fast path returns\npcount << PAGE_SHIFT, ignoring the incoming poffset, unlike the\ndecompression path which returns bytes produced relative to poffset.\nzisofs_fill_pages() uses that return to advance its page cursor, so when\nthe zisofs block size is below PAGE_SIZE and a sub-page block leaves\npoffset partway into a page, a following empty block over-counts and\nadvances pages[] one element past its end, after which\n\"if (poffset && *pages)\" reads pages[1] out of bounds.  rock.c only\nrejects a block-size shift > 17, so a crafted \"ZF\" Rock Ridge record can\nset it below PAGE_SHIFT; the bug is reached by an ordinary read() of a\ncompressed file on such a mounted ISO9660 image.\n\nReturn the byte count relative to poffset and zero only\n[poffset, PAGE_SIZE) of the first page, matching the decompression path.\nThe page-aligned case (poffset == 0) is unaffected.\n\n  BUG: KASAN: slab-out-of-bounds in zisofs_read_folio (fs/isofs/compress.c:290)\n  Read of size 8 at addr ffff88800f5eac48 by task exploit/142\n   zisofs_read_folio (fs/isofs/compress.c:290)\n   read_pages (mm/readahead.c:184)\n   ...\n   filemap_read (mm/filemap.c:2814)\n   vfs_read (fs/read_write.c:574)\n   __x64_sys_pread64 (fs/read_write.c:769)\n   do_syscall_64 (arch/x86/entry/syscall_64.c:94)\n   entry_SYSCALL_64_after_hwframe (arch/x86/entry/entry_64.S:121)\n  The buggy address is located 0 bytes to the right of the\n  allocated 8-byte region in the kmalloc-8 cache\n\n## Remediation\n\nRefer to the linked advisories for vendor-supplied fixes and affected version ranges.","depth":"midnight","depthScore":54,"depthScoreParts":{"impact":53.9,"likelihood":0.1,"exploitation":0,"ransomware":0},"changes":[{"seq":205271,"id":"CVE-2026-89778","ts":1789570706033,"field":"cvss","old":null,"new":"9.8"},{"seq":205270,"id":"CVE-2026-89778","ts":1789570706033,"field":"severity","old":"none","new":"critical"}]}