isofs: fix out-of-bounds page array access on empty zisofs block

MITRE NVD CVE.ORG JSON API

Summary

CVECVE-2026-89778
StatePUBLISHED
AssignerLinux
Source PriorityCVE Program / NVD first with legacy fallback
Published2026-09-16 09:17:08 UTC
Updated2026-09-16 15:18:07 UTC
DescriptionIn 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

Risk And Classification

Primary CVSS: v3.1 9.8 CRITICAL from 416baaa9-dc9f-4396-8d5f-8c081fb06d67

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H

EPSS: 0.002050000 probability, percentile 0.108070000 (date 2026-09-16)

VersionSourceTypeScoreSeverityVector
3.1416baaa9-dc9f-4396-8d5f-8c081fb06d67Secondary9.8CRITICALCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
3.1CNADECLARED9.8CRITICALCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H

CVSS v3.1 Breakdown

Attack Vector
Network
Attack Complexity
Low
Privileges Required
None
User Interaction
None
Scope
Unchanged
Confidentiality
High
Integrity
High
Availability
High

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H

Vendor Declared Affected Products

SourceVendorProductVersionPlatforms
CNA Linux Linux affected 59bc055211b8d266ab6089158058bf8268e02006 8b994ac5778a725982fd6a8a3afcaa068d4a93e3 git Not specified
CNA Linux Linux affected 59bc055211b8d266ab6089158058bf8268e02006 ad3249cdf9d4ba34bb8b1ff3956a4020fdfb5b0a git Not specified
CNA Linux Linux affected 59bc055211b8d266ab6089158058bf8268e02006 85904076cece72ee3194646ad7ac8e6659d999aa git Not specified
CNA Linux Linux affected 59bc055211b8d266ab6089158058bf8268e02006 f03425dcbe04aec3c27b9917e97d7d23a2908dda git Not specified
CNA Linux Linux affected 59bc055211b8d266ab6089158058bf8268e02006 cd616aa0449a772a6956abf03358f0ff31720580 git Not specified
CNA Linux Linux affected 59bc055211b8d266ab6089158058bf8268e02006 9c6eace8d07e90f038c89eb3b756d65a7e259d48 git Not specified
CNA Linux Linux affected 59bc055211b8d266ab6089158058bf8268e02006 68d4d3e78150c7ed7d1195af63ad1e6ace30c661 git Not specified
CNA Linux Linux affected 2.6.33 Not specified
CNA Linux Linux unaffected 2.6.33 semver Not specified
CNA Linux Linux unaffected 5.15.221 5.15.* semver Not specified
CNA Linux Linux unaffected 6.1.188 6.1.* semver Not specified
CNA Linux Linux unaffected 6.6.157 6.6.* semver Not specified
CNA Linux Linux unaffected 6.12.110 6.12.* semver Not specified
CNA Linux Linux unaffected 6.18.52 6.18.* semver Not specified
CNA Linux Linux unaffected 7.2.6 7.2.* semver Not specified
CNA Linux Linux unaffected 7.3-rc1 * original_commit_for_fix Not specified

References

ReferenceSourceLinkTags
git.kernel.org/stable/c/ad3249cdf9d4ba34bb8b1ff3956a4020fdfb5b0a 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org
git.kernel.org/stable/c/8b994ac5778a725982fd6a8a3afcaa068d4a93e3 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org
git.kernel.org/stable/c/68d4d3e78150c7ed7d1195af63ad1e6ace30c661 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org
git.kernel.org/stable/c/f03425dcbe04aec3c27b9917e97d7d23a2908dda 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org
git.kernel.org/stable/c/85904076cece72ee3194646ad7ac8e6659d999aa 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org
git.kernel.org/stable/c/cd616aa0449a772a6956abf03358f0ff31720580 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org
git.kernel.org/stable/c/9c6eace8d07e90f038c89eb3b756d65a7e259d48 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org
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