---
cve: "CVE-2026-63815"
severity: "HIGH"
cvss: 8.4
epss: "0.1%"
vendor: "Linux"
kev: false
exploited: false
published: "2026-07-19 12:16:54"
tags: [cve, security, high]
source: tsecurity.de CVE-Dossier
exported: "2026-09-20T16:07:46+02:00"
---

# CVE-2026-63815

> 8.4 HIGH

## Beschreibung

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.

## CVSS-Vektor

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

| Metrik | Wert | Bewertung |
|---|---|---|
| AV Angriffsvektor | Lokal | good |
| AC Komplexität | Gering | bad |
| PR Privilegien | Keine | bad |
| UI Interaktion | Keine | bad |
| S Scope | Unverändert | good |
| C Vertraulichkeit | Hoch | bad |
| I Integrität | Hoch | bad |
| A Verfügbarkeit | Hoch | bad |

## Patch verfügbar (OSV)

- Kernel ≥ 5.10.261
- Kernel ≥ 5.15.212
- Kernel ≥ 6.1.178
- Kernel ≥ 6.6.145
- Kernel ≥ 6.12.96
- Kernel ≥ 6.18.39
- Kernel ≥ 7.1.3

## Referenzen

- <https://git.kernel.org/stable/c/3c8d6b4093aea40a20596f452289e7c22d84e6d5>
- <https://git.kernel.org/stable/c/a08ee30dcbeff6b97df75c38c2589603ddde53a6>
- <https://git.kernel.org/stable/c/c3e05522daae4e7348a1ea81eeb321d25aa0fd3b>
- <https://git.kernel.org/stable/c/76e1a05cf6d4051931d7fa4ead51a05786a62918>
- <https://git.kernel.org/stable/c/2a9f9791653ba5ed3fb45bbffa8d63a7cd5cf706>
- <https://git.kernel.org/stable/c/4ce2d52f680c1d8bfdad7cce05b815ea7ca9790d>
- <https://git.kernel.org/stable/c/16bc237ce3c483b75575abea53cfb639745311ed>
- <https://git.kernel.org/stable/c/378acf3cf19b6af6cba55e8dd1154c4e1504bae8>

---
_Exportiert aus dem [tsecurity.de CVE-Dossier](https://tsecurity.de/cve?cve=CVE-2026-63815) · Datenquellen: EUVD (ENISA), NVD, OSV, CISA KEV, FIRST EPSS, Exploit-DB, BSI BITS_