Bug 2414744 (CVE-2025-40198)

Summary: CVE-2025-40198 kernel: ext4: avoid potential buffer over-read in parse_apply_sb_mount_options()
Product: [Other] Security Response Reporter: OSIDB Bzimport <bzimport>
Component: vulnerabilityAssignee: Product Security DevOps Team <prodsec-dev>
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Priority: low    
Version: unspecifiedKeywords: Security
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OS: Linux   
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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.
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Description OSIDB Bzimport 2025-11-12 23:03:59 UTC 
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.
Comment 1 Alexander B 2025-11-13 10:21:50 UTC 
Upstream advisory:
https://lore.kernel.org/linux-cve-announce/2025111246-CVE-2025-40198-7a99@gregkh/T