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

Type: advisorySource: Official CVE List1 source record

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

Announced Source revision 1
Original source ↗

CVE-2026-89778

Primary source · Revision 1

Imported from structured advisory data. Source references identify upstream records or fields; verify affected versions and your deployed configuration.

Security context

Source reference: cve:CVE-2026-89778

Linux

Source reference: /containers/cna/affected/0/product

Affected versions
Not stated in this record
Fixed versions
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Prerequisites
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Linux

Source reference: /containers/cna/affected/1/product

Affected versions
Not stated in this record
Fixed versions
Not stated in this record
Prerequisites
Not stated in this record

Structured affected-version data

Original package identities and version rules from this source.

[
  {
    "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
    "vendor": "Linux",
    "product": "Linux",
    "versions": [
      {
        "status": "affected",
        "version": "59bc055211b8d266ab6089158058bf8268e02006",
        "lessThan": "8b994ac5778a725982fd6a8a3afcaa068d4a93e3",
        "versionType": "git"
      },
      {
        "status": "affected",
        "version": "59bc055211b8d266ab6089158058bf8268e02006",
        "lessThan": "ad3249cdf9d4ba34bb8b1ff3956a4020fdfb5b0a",
        "versionType": "git"
      },
      {
        "status": "affected",
        "version": "59bc055211b8d266ab6089158058bf8268e02006",
        "lessThan": "85904076cece72ee3194646ad7ac8e6659d999aa",
        "versionType": "git"
      },
      {
        "status": "affected",
        "version": "59bc055211b8d266ab6089158058bf8268e02006",
        "lessThan": "f03425dcbe04aec3c27b9917e97d7d23a2908dda",
        "versionType": "git"
      },
      {
        "status": "affected",
        "version": "59bc055211b8d266ab6089158058bf8268e02006",
        "lessThan": "cd616aa0449a772a6956abf03358f0ff31720580",
        "versionType": "git"
      },
      {
        "status": "affected",
        "version": "59bc055211b8d266ab6089158058bf8268e02006",
        "lessThan": "9c6eace8d07e90f038c89eb3b756d65a7e259d48",
        "versionType": "git"
      },
      {
        "status": "affected",
        "version": "59bc055211b8d266ab6089158058bf8268e02006",
        "lessThan": "68d4d3e78150c7ed7d1195af63ad1e6ace30c661",
        "versionType": "git"
      }
    ],
    "programFiles": [
      "fs/isofs/compress.c"
    ],
    "defaultStatus": "unaffected"
  },
  {
    "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
    "vendor": "Linux",
    "product": "Linux",
    "versions": [
      {
        "status": "affected",
        "version": "2.6.33"
      },
      {
        "status": "unaffected",
        "version": "0",
        "lessThan": "2.6.33",
        "versionType": "semver"
      },
      {
        "status": "unaffected",
        "version": "5.15.221",
        "versionType": "semver",
        "lessThanOrEqual": "5.15.*"
      },
      {
        "status": "unaffected",
        "version": "6.1.188",
        "versionType": "semver",
        "lessThanOrEqual": "6.1.*"
      },
      {
        "status": "unaffected",
        "version": "6.6.157",
        "versionType": "semver",
        "lessThanOrEqual": "6.6.*"
      },
      {
        "status": "unaffected",
        "version": "6.12.110",
        "versionType": "semver",
        "lessThanOrEqual": "6.12.*"
      },
      {
        "status": "unaffected",
        "version": "6.18.52",
        "versionType": "semver",
        "lessThanOrEqual": "6.18.*"
      },
      {
        "status": "unaffected",
        "version": "7.2.6",
        "versionType": "semver",
        "lessThanOrEqual": "7.2.*"
      },
      {
        "status": "unaffected",
        "version": "7.3",
        "versionType": "original_commit_for_fix",
        "lessThanOrEqual": "*"
      }
    ],
    "programFiles": [
      "fs/isofs/compress.c"
    ],
    "defaultStatus": "affected"
  }
]
Related CVEs
CVE-2026-89778

Source reference: /cveMetadata/cveId

Publisher severity

critical

Source reference: /containers/cna/metrics

Event
#35245 · Revision 1
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