{"id":"CVE-2026-63815","url":"https://www.cyber-defence.io/tools/cve/CVE-2026-63815","generatedAt":"2026-10-28T07:05:17.759Z","title":"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…","description":"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->i_inline_xattr_size = le16_to_cpu(ri->i_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->max (int) to a negative\nvalue.  The inline directory walk then compares an unsigned long bit_pos\nagainst that negative d->max, which is promoted to a huge unsigned bound,\nand reads far past the inline area:\n\n\twhile (bit_pos < d->max)\t\t/* fs/f2fs/dir.c */\n\t\t... test_bit_le(bit_pos, d->bitmap) / d->dentry[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.","published":"2026-07-19T12:16:55.000Z","lastModified":"2026-08-17T05:17:19.000Z","status":"Awaiting Analysis","sourceIdentifier":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","cvss":{"version":"3.1","score":8.4,"severity":"HIGH","vector":"CVSS:3.1/AV:L/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H"},"cwe":[],"affected":[],"epss":{"score":0.00139,"percentile":0.03273,"date":"2026-10-27","history":[]},"kev":{"listed":false},"exploits":{"count":0,"verified":false,"firstPublished":null,"source":"Exploit-DB (https://gitlab.com/exploit-database/exploitdb)","entries":[]},"verdict":{"level":"high","text":"High impact if exploited, but EPSS currently rates exploitation as unlikely (0.14%). Schedule it in the normal patch cycle and watch for a rise in EPSS or a public exploit."},"changes":[],"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/3c8d6b4093aea40a20596f452289e7c22d84e6d5","source":"416baaa9-dc9f-4396-8d5f-8c081fb06d67"},{"url":"https://git.kernel.org/stable/c/4ce2d52f680c1d8bfdad7cce05b815ea7ca9790d","source":"416baaa9-dc9f-4396-8d5f-8c081fb06d67"},{"url":"https://git.kernel.org/stable/c/76e1a05cf6d4051931d7fa4ead51a05786a62918","source":"416baaa9-dc9f-4396-8d5f-8c081fb06d67"},{"url":"https://git.kernel.org/stable/c/a08ee30dcbeff6b97df75c38c2589603ddde53a6","source":"416baaa9-dc9f-4396-8d5f-8c081fb06d67"},{"url":"https://git.kernel.org/stable/c/c3e05522daae4e7348a1ea81eeb321d25aa0fd3b","source":"416baaa9-dc9f-4396-8d5f-8c081fb06d67"}],"sources":{"nvd":"https://nvd.nist.gov/vuln/detail/CVE-2026-63815","epss":"https://www.first.org/epss/","kev":"https://www.cisa.gov/known-exploited-vulnerabilities-catalog","exploitdb":"https://www.exploit-db.com/"},"licence":"CC BY 4.0 — link back to the CVE Explorer if you publish the results; upstream data remains subject to its own terms."}