CVE-2025-40198
Description
A buffer over-read vulnerability was found in the Linux kernel's ext4 filesystem when parsing mount options stored in the superblock. A local user can trigger this issue by mounting a maliciously crafted ext4 filesystem where the s_mount_opts string field lacks proper NULL termination. During mount option parsing, the code reads beyond the field's boundaries searching for the terminator, potentially accessing invalid memory and causing kernel crashes or denial of service.
Statement
The s_mount_opts field in ext4 superblocks is parsed at mount time, with the kernel relying on tune2fs to ensure NUL termination. If a malicious image lacks proper termination, parse_apply_sb_mount_options walks past the field boundary searching for the NUL byte, potentially reading adjacent superblock fields or unmapped memory. The fix treats s_mount_opts as potentially unterminated and adds explicit bounds checking during parsing.
Common Vulnerability Scoring System (CVSS) Score Details
Info alert:Important note
CVSS scores for open source components depend on vendor-specific factors (e.g. version or build chain). Therefore, Red Hat's score and impact rating can be different from NVD and other vendors. Red Hat remains the authoritative CVE Naming Authority (CNA) source for its products and services (see Red Hat classifications).
The following CVSS metrics and score provided are preliminary and subject to review.
CVSS v3 Score Breakdown
| Red Hat | NVD | cve.org | |
|---|---|---|---|
| Base Score | 4.4 | N/A | 7.8 |
| Attack Vector | Local | N/A | Local |
| Attack Complexity | Low | N/A | Low |
| Privileges Required | High | N/A | None |
| User Interaction | None | N/A | Required |
| Scope | Unchanged | N/A | Unchanged |
| Confidentiality | None | N/A | High |
| Integrity Impact | None | N/A | High |
| Availability Impact | High | N/A | High |
Vector
Red Hat: CVSS:3.1/AV:L/AC:L/PR:H/UI:N/S:U/C:N/I:N/A:H
cve.org: CVSS:3.1/AV:L/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H
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