CVE-2026-89778 (GCVE-0-2026-89778)
Vulnerability from cvelistv5
Published
2026-09-16 08:48
Modified
2026-10-19 08:52
Severity ?
9.8 (Critical) - CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
Summary
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
References
Impacted products
Vendor Product Version
Linux Linux Version: 59bc055211b8d266ab6089158058bf8268e02006
Version: 59bc055211b8d266ab6089158058bf8268e02006
Version: 59bc055211b8d266ab6089158058bf8268e02006
Version: 59bc055211b8d266ab6089158058bf8268e02006
Version: 59bc055211b8d266ab6089158058bf8268e02006
Version: 59bc055211b8d266ab6089158058bf8268e02006
Version: 59bc055211b8d266ab6089158058bf8268e02006
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{
  "containers": {
    "cna": {
      "affected": [
        {
          "defaultStatus": "unaffected",
          "product": "Linux",
          "programFiles": [
            "fs/isofs/compress.c"
          ],
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          "vendor": "Linux",
          "versions": [
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            }
          ]
        },
        {
          "defaultStatus": "affected",
          "product": "Linux",
          "programFiles": [
            "fs/isofs/compress.c"
          ],
          "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
          "vendor": "Linux",
          "versions": [
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              "version": "2.6.33"
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              "version": "0",
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              "version": "6.6.157",
              "versionType": "semver"
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              "lessThanOrEqual": "6.12.*",
              "status": "unaffected",
              "version": "6.12.110",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "6.18.*",
              "status": "unaffected",
              "version": "6.18.52",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "7.2.*",
              "status": "unaffected",
              "version": "7.2.6",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "*",
              "status": "unaffected",
              "version": "7.3",
              "versionType": "original_commit_for_fix"
            }
          ]
        }
      ],
      "cpeApplicability": [
        {
          "nodes": [
            {
              "cpeMatch": [
                {
                  "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
                  "versionEndExcluding": "5.15.221",
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                  "vulnerable": true
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                  "versionEndExcluding": "6.1.188",
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              ],
              "negate": false,
              "operator": "OR"
            }
          ]
        }
      ],
      "descriptions": [
        {
          "lang": "en",
          "value": "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()\u0027s empty-block fast path returns\npcount \u003c\u003c 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 \u0026\u0026 *pages)\" reads pages[1] out of bounds.  rock.c only\nrejects a block-size shift \u003e 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"
        }
      ],
      "metrics": [
        {
          "cvssV3_1": {
            "baseScore": 9.8,
            "baseSeverity": "CRITICAL",
            "vectorString": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H",
            "version": "3.1"
          },
          "scenarios": [
            {
              "lang": "en",
              "value": "AV:N - isofs assigns s_export_op to isofs_export_ops; nfsd_read then nfsd_iter_read (vfs_iocb_iter_read) and ksmbd_vfs_read (kernel_read) perform VFS reads that reach generic_file_read_iter, filemap_read, and zisofs_read_folio, so a remote NFS or SMB client can trigger the bug on a host exporting a crafted ISO9660 image.\nAC:L - The attacker fully controls the Rock Ridge ZF parms (rock.c only rejects block_shift \u003e 17) and the zisofs block pointer table; a block_shift below PAGE_SHIFT plus a nonempty sub-page block followed by an empty block (block_start==block_end) deterministically over-advances pages[] with no race.\nPR:N - A remote NFS or SMB client needs only read access to an exported iso9660 tree; AUTH_SYS media-server exports commonly require no host credentials, and compressed regular files default to S_IRUGO. No CAP_SYS_ADMIN on the victim host is required on the read path.\nUI:N - Once an iso9660 volume containing the crafted zisofs file is exported, the NFS or SMB server processes the client\u0027s READ automatically; no separate victim must open a file or click a dialog at attack time beyond that pre-existing export.\nS:U - The slab out-of-bounds pointer load and any memzero_page or SetPageUptodate side effects remain inside the host kernel; this is not a VM escape, IOMMU/DMA bypass, or other cross-authority boundary.\nC:H - zisofs_fill_pages loads an 8-byte pointer from one slot past a kmalloc-8 pages[] allocation and may treat adjacent heap data as a struct page. With heap grooming this memory corruption can be turned into a kernel information-disclosure primitive, so confidentiality impact is High.\nI:H - When the out-of-bounds pointer is non-NULL, memzero_page() writes zeros through kmap_local_page() of the forged page and SetPageUptodate() corrupts page flags, yielding a kernel write primitive against attacker-groomed heap or page objects that can be chained to control-flow hijack.\nA:H - KASAN reports a slab-out-of-bounds read in zisofs_read_folio; feeding a non-page pointer to kmap_local_page or memzero_page oopses or panics the kernel, and the attacker can repeat the NFS, SMB, or local read at will."
            }
          ]
        }
      ],
      "providerMetadata": {
        "dateUpdated": "2026-10-19T08:52:30.510Z",
        "orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
        "shortName": "Linux"
      },
      "references": [
        {
          "url": "https://git.kernel.org/stable/c/8b994ac5778a725982fd6a8a3afcaa068d4a93e3"
        },
        {
          "url": "https://git.kernel.org/stable/c/ad3249cdf9d4ba34bb8b1ff3956a4020fdfb5b0a"
        },
        {
          "url": "https://git.kernel.org/stable/c/85904076cece72ee3194646ad7ac8e6659d999aa"
        },
        {
          "url": "https://git.kernel.org/stable/c/f03425dcbe04aec3c27b9917e97d7d23a2908dda"
        },
        {
          "url": "https://git.kernel.org/stable/c/cd616aa0449a772a6956abf03358f0ff31720580"
        },
        {
          "url": "https://git.kernel.org/stable/c/9c6eace8d07e90f038c89eb3b756d65a7e259d48"
        },
        {
          "url": "https://git.kernel.org/stable/c/68d4d3e78150c7ed7d1195af63ad1e6ace30c661"
        }
      ],
      "title": "isofs: fix out-of-bounds page array access on empty zisofs block",
      "x_generator": {
        "engine": "bippy-1.2.0"
      }
    }
  },
  "cveMetadata": {
    "assignerOrgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
    "assignerShortName": "Linux",
    "cveId": "CVE-2026-89778",
    "datePublished": "2026-09-16T08:48:18.407Z",
    "dateReserved": "2026-09-11T19:38:34.765Z",
    "dateUpdated": "2026-10-19T08:52:30.510Z",
    "state": "PUBLISHED"
  },
  "dataType": "CVE_RECORD",
  "dataVersion": "5.2"
}


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