CVE-2026-63815 (GCVE-0-2026-63815)

Vulnerability from cvelistv5 – Published: 2026-07-19 12:02 – Updated: 2026-07-20 13:40
VLAI
Title
f2fs: bound i_inline_xattr_size for non-inline-xattr inodes
Summary
In the Linux kernel, the following vulnerability has been resolved: f2fs: bound i_inline_xattr_size for non-inline-xattr inodes When the flexible_inline_xattr feature is enabled, do_read_inode() loads the on-disk i_inline_xattr_size unconditionally: if (f2fs_sb_has_flexible_inline_xattr(sbi)) fi->i_inline_xattr_size = le16_to_cpu(ri->i_inline_xattr_size); but sanity_check_inode() only range-checks it when the inode also has the FI_INLINE_XATTR flag set. An inode that carries an inline dentry or inline data but not FI_INLINE_XATTR -- the normal layout for an inline directory -- therefore keeps a fully attacker-controlled i_inline_xattr_size from a crafted image. get_inline_xattr_addrs() returns that value with no flag gating, so it feeds the inode geometry: MAX_INLINE_DATA() = 4 * (CUR_ADDRS_PER_INODE - i_inline_xattr_size - 1) NR_INLINE_DENTRY() = MAX_INLINE_DATA() * BITS_PER_BYTE / (...) addrs_per_page() = CUR_ADDRS_PER_INODE - i_inline_xattr_size A large i_inline_xattr_size drives MAX_INLINE_DATA() and NR_INLINE_DENTRY() negative, so make_dentry_ptr_inline() sets d->max (int) to a negative value. The inline directory walk then compares an unsigned long bit_pos against that negative d->max, which is promoted to a huge unsigned bound, and reads far past the inline area: while (bit_pos < d->max) /* fs/f2fs/dir.c */ ... test_bit_le(bit_pos, d->bitmap) / d->dentry[bit_pos] ... Mounting a crafted image and reading such a directory triggers an out-of-bounds read in f2fs_fill_dentries(); the same underflow also corrupts ADDRS_PER_INODE for regular files. Validate i_inline_xattr_size against MAX_INLINE_XATTR_SIZE whenever the flexible_inline_xattr feature is enabled -- i.e. whenever the value is loaded from disk and consumed -- and keep the lower MIN_INLINE_XATTR_SIZE bound gated on inodes that actually carry an inline xattr, so legitimate inodes with i_inline_xattr_size == 0 are still accepted.
Severity
8.4 (High)
CVSS:3.1/AV:L/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
Assigner
References
Impacted products
Vendor Product Version
Linux Linux Affected: 6afc662e68b5f988282ff20afd58a89b1c279dca , < 2a9f9791653ba5ed3fb45bbffa8d63a7cd5cf706 (git)
Affected: 6afc662e68b5f988282ff20afd58a89b1c279dca , < 4ce2d52f680c1d8bfdad7cce05b815ea7ca9790d (git)
Affected: 6afc662e68b5f988282ff20afd58a89b1c279dca , < 16bc237ce3c483b75575abea53cfb639745311ed (git)
Affected: 6afc662e68b5f988282ff20afd58a89b1c279dca , < 378acf3cf19b6af6cba55e8dd1154c4e1504bae8 (git)
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Linux Linux Affected: 4.15
Unaffected: 0 , < 4.15 (semver)
Unaffected: 6.12.96 , ≤ 6.12.* (semver)
Unaffected: 6.18.39 , ≤ 6.18.* (semver)
Unaffected: 7.1.3 , ≤ 7.1.* (semver)
Unaffected: 7.2-rc1 , ≤ * (original_commit_for_fix)
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          "programFiles": [
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              "version": "0",
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              "versionType": "semver"
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          "lang": "en",
          "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nf2fs: bound i_inline_xattr_size for non-inline-xattr inodes\n\nWhen the flexible_inline_xattr feature is enabled, do_read_inode() loads\nthe on-disk i_inline_xattr_size unconditionally:\n\n\tif (f2fs_sb_has_flexible_inline_xattr(sbi))\n\t\tfi-\u003ei_inline_xattr_size = le16_to_cpu(ri-\u003ei_inline_xattr_size);\n\nbut sanity_check_inode() only range-checks it when the inode also has the\nFI_INLINE_XATTR flag set.  An inode that carries an inline dentry or inline\ndata but not FI_INLINE_XATTR -- the normal layout for an inline\ndirectory -- therefore keeps a fully attacker-controlled\ni_inline_xattr_size from a crafted image.\n\nget_inline_xattr_addrs() returns that value with no flag gating, so it\nfeeds the inode geometry:\n\n\tMAX_INLINE_DATA()  = 4 * (CUR_ADDRS_PER_INODE - i_inline_xattr_size - 1)\n\tNR_INLINE_DENTRY() = MAX_INLINE_DATA() * BITS_PER_BYTE / (...)\n\taddrs_per_page()   = CUR_ADDRS_PER_INODE - i_inline_xattr_size\n\nA large i_inline_xattr_size drives MAX_INLINE_DATA() and NR_INLINE_DENTRY()\nnegative, so make_dentry_ptr_inline() sets d-\u003emax (int) to a negative\nvalue.  The inline directory walk then compares an unsigned long bit_pos\nagainst that negative d-\u003emax, which is promoted to a huge unsigned bound,\nand reads far past the inline area:\n\n\twhile (bit_pos \u003c d-\u003emax)\t\t/* fs/f2fs/dir.c */\n\t\t... test_bit_le(bit_pos, d-\u003ebitmap) / d-\u003edentry[bit_pos] ...\n\nMounting a crafted image and reading such a directory triggers an\nout-of-bounds read in f2fs_fill_dentries(); the same underflow also\ncorrupts ADDRS_PER_INODE for regular files.\n\nValidate i_inline_xattr_size against MAX_INLINE_XATTR_SIZE whenever the\nflexible_inline_xattr feature is enabled -- i.e. whenever the value is\nloaded from disk and consumed -- and keep the lower MIN_INLINE_XATTR_SIZE\nbound gated on inodes that actually carry an inline xattr, so legitimate\ninodes with i_inline_xattr_size == 0 are still accepted."
        }
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            "baseScore": 8.4,
            "baseSeverity": "HIGH",
            "vectorString": "CVSS:3.1/AV:L/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H",
            "version": "3.1"
          }
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      "providerMetadata": {
        "dateUpdated": "2026-07-20T13:40:22.588Z",
        "orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
        "shortName": "Linux"
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          "url": "https://git.kernel.org/stable/c/4ce2d52f680c1d8bfdad7cce05b815ea7ca9790d"
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        {
          "url": "https://git.kernel.org/stable/c/378acf3cf19b6af6cba55e8dd1154c4e1504bae8"
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    "cveId": "CVE-2026-63815",
    "datePublished": "2026-07-19T12:02:15.345Z",
    "dateReserved": "2026-07-19T07:54:57.014Z",
    "dateUpdated": "2026-07-20T13:40:22.588Z",
    "state": "PUBLISHED"
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      "percentile": "0.03158"
    },
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      "cve": "CVE-2026-63815",
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      "initial_release_date": "2026-07-20T01:01:23.000Z",
      "product_status:known_affected": "1",
      "source": "Microsoft CSAF VEX",
      "status": "final",
      "title": "f2fs: bound i_inline_xattr_size for non-inline-xattr inodes",
      "url": "https://msrc.microsoft.com/csaf/vex/2026/msrc_cve-2026-63815.json",
      "version": "2"
    },
    "nvd": "{\"cve\":{\"id\":\"CVE-2026-63815\",\"sourceIdentifier\":\"416baaa9-dc9f-4396-8d5f-8c081fb06d67\",\"published\":\"2026-07-19T12:16:54.527\",\"lastModified\":\"2026-07-20T15:16:48.347\",\"vulnStatus\":\"Received\",\"cveTags\":[],\"descriptions\":[{\"lang\":\"en\",\"value\":\"In the Linux kernel, the following vulnerability has been resolved:\\n\\nf2fs: bound i_inline_xattr_size for non-inline-xattr inodes\\n\\nWhen the flexible_inline_xattr feature is enabled, do_read_inode() loads\\nthe on-disk i_inline_xattr_size unconditionally:\\n\\n\\tif (f2fs_sb_has_flexible_inline_xattr(sbi))\\n\\t\\tfi-\u003ei_inline_xattr_size = le16_to_cpu(ri-\u003ei_inline_xattr_size);\\n\\nbut sanity_check_inode() only range-checks it when the inode also has the\\nFI_INLINE_XATTR flag set.  An inode that carries an inline dentry or inline\\ndata but not FI_INLINE_XATTR -- the normal layout for an inline\\ndirectory -- therefore keeps a fully attacker-controlled\\ni_inline_xattr_size from a crafted image.\\n\\nget_inline_xattr_addrs() returns that value with no flag gating, so it\\nfeeds the inode geometry:\\n\\n\\tMAX_INLINE_DATA()  = 4 * (CUR_ADDRS_PER_INODE - i_inline_xattr_size - 1)\\n\\tNR_INLINE_DENTRY() = MAX_INLINE_DATA() * BITS_PER_BYTE / (...)\\n\\taddrs_per_page()   = CUR_ADDRS_PER_INODE - i_inline_xattr_size\\n\\nA large i_inline_xattr_size drives MAX_INLINE_DATA() and NR_INLINE_DENTRY()\\nnegative, so make_dentry_ptr_inline() sets d-\u003emax (int) to a negative\\nvalue.  The inline directory walk then compares an unsigned long bit_pos\\nagainst that negative d-\u003emax, which is promoted to a huge unsigned bound,\\nand reads far past the inline area:\\n\\n\\twhile (bit_pos \u003c d-\u003emax)\\t\\t/* fs/f2fs/dir.c */\\n\\t\\t... test_bit_le(bit_pos, d-\u003ebitmap) / d-\u003edentry[bit_pos] ...\\n\\nMounting a crafted image and reading such a directory triggers an\\nout-of-bounds read in f2fs_fill_dentries(); the same underflow also\\ncorrupts ADDRS_PER_INODE for regular files.\\n\\nValidate i_inline_xattr_size against MAX_INLINE_XATTR_SIZE whenever the\\nflexible_inline_xattr feature is enabled -- i.e. whenever the value is\\nloaded from disk and consumed -- and keep the lower MIN_INLINE_XATTR_SIZE\\nbound gated on inodes that actually carry an inline xattr, so legitimate\\ninodes with i_inline_xattr_size == 0 are still accepted.\"}],\"affected\":[{\"source\":\"416baaa9-dc9f-4396-8d5f-8c081fb06d67\",\"affectedData\":[{\"vendor\":\"Linux\",\"product\":\"Linux\",\"defaultStatus\":\"unaffected\",\"programFiles\":[\"fs/f2fs/inode.c\"],\"repo\":\"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git\",\"versions\":[{\"version\":\"6afc662e68b5f988282ff20afd58a89b1c279dca\",\"lessThan\":\"2a9f9791653ba5ed3fb45bbffa8d63a7cd5cf706\",\"versionType\":\"git\",\"status\":\"affected\"},{\"version\":\"6afc662e68b5f988282ff20afd58a89b1c279dca\",\"lessThan\":\"4ce2d52f680c1d8bfdad7cce05b815ea7ca9790d\",\"versionType\":\"git\",\"status\":\"affected\"},{\"version\":\"6afc662e68b5f988282ff20afd58a89b1c279dca\",\"lessThan\":\"16bc237ce3c483b75575abea53cfb639745311ed\",\"versionType\":\"git\",\"status\":\"affected\"},{\"version\":\"6afc662e68b5f988282ff20afd58a89b1c279dca\",\"lessThan\":\"378acf3cf19b6af6cba55e8dd1154c4e1504bae8\",\"versionType\":\"git\",\"status\":\"affected\"}]},{\"vendor\":\"Linux\",\"product\":\"Linux\",\"defaultStatus\":\"affected\",\"programFiles\":[\"fs/f2fs/inode.c\"],\"repo\":\"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git\",\"versions\":[{\"version\":\"4.15\",\"status\":\"affected\"},{\"version\":\"0\",\"lessThan\":\"4.15\",\"versionType\":\"semver\",\"status\":\"unaffected\"},{\"version\":\"6.12.96\",\"lessThanOrEqual\":\"6.12.*\",\"versionType\":\"semver\",\"status\":\"unaffected\"},{\"version\":\"6.18.39\",\"lessThanOrEqual\":\"6.18.*\",\"versionType\":\"semver\",\"status\":\"unaffected\"},{\"version\":\"7.1.3\",\"lessThanOrEqual\":\"7.1.*\",\"versionType\":\"semver\",\"status\":\"unaffected\"},{\"version\":\"7.2-rc1\",\"lessThanOrEqual\":\"*\",\"versionType\":\"original_commit_for_fix\",\"status\":\"unaffected\"}]}]}],\"metrics\":{\"cvssMetricV31\":[{\"source\":\"416baaa9-dc9f-4396-8d5f-8c081fb06d67\",\"type\":\"Secondary\",\"cvssData\":{\"version\":\"3.1\",\"vectorString\":\"CVSS:3.1/AV:L/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H\",\"baseScore\":8.4,\"baseSeverity\":\"HIGH\",\"attackVector\":\"LOCAL\",\"attackComplexity\":\"LOW\",\"privilegesRequired\":\"NONE\",\"userInteraction\":\"NONE\",\"scope\":\"UNCHANGED\",\"confidentialityImpact\":\"HIGH\",\"integrityImpact\":\"HIGH\",\"availabilityImpact\":\"HIGH\"},\"exploitabilityScore\":2.5,\"impactScore\":5.9}]},\"references\":[{\"url\":\"https://git.kernel.org/stable/c/16bc237ce3c483b75575abea53cfb639745311ed\",\"source\":\"416baaa9-dc9f-4396-8d5f-8c081fb06d67\"},{\"url\":\"https://git.kernel.org/stable/c/2a9f9791653ba5ed3fb45bbffa8d63a7cd5cf706\",\"source\":\"416baaa9-dc9f-4396-8d5f-8c081fb06d67\"},{\"url\":\"https://git.kernel.org/stable/c/378acf3cf19b6af6cba55e8dd1154c4e1504bae8\",\"source\":\"416baaa9-dc9f-4396-8d5f-8c081fb06d67\"},{\"url\":\"https://git.kernel.org/stable/c/4ce2d52f680c1d8bfdad7cce05b815ea7ca9790d\",\"source\":\"416baaa9-dc9f-4396-8d5f-8c081fb06d67\"}]}}",
    "redhat_vex": {
      "aggregate_severity": "None",
      "current_release_date": "2026-07-21T08:02:06+00:00",
      "cve": "CVE-2026-63815",
      "id": "CVE-2026-63815",
      "initial_release_date": "2026-07-19T00:00:00+00:00",
      "product_status:known_not_affected": "274",
      "source": "Red Hat CSAF VEX",
      "status": "final",
      "title": "kernel: f2fs: bound i_inline_xattr_size for non-inline-xattr inodes",
      "url": "https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-63815.json",
      "version": "3"
    }
  }
}



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Forecast uses a logistic model when the trend is rising, or an exponential decay model when the trend is falling. Fitted via linearized least squares.

Sightings

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Nomenclature

  • Seen: The vulnerability was mentioned, discussed, or observed by the user.
  • Confirmed: The vulnerability has been validated from an analyst's perspective.
  • Published Proof of Concept: A public proof of concept is available for this vulnerability.
  • Exploited: The vulnerability was observed as exploited by the user who reported the sighting.
  • Patched: The vulnerability was observed as successfully patched by the user who reported the sighting.
  • Not exploited: The vulnerability was not observed as exploited by the user who reported the sighting.
  • Not confirmed: The user expressed doubt about the validity of the vulnerability.
  • Not patched: The vulnerability was not observed as successfully patched by the user who reported the sighting.


Detection rules are retrieved from Rulezet.