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CVE Record

CVE-2025-71123: ext4: fix string copying in parse_apply_sb_mount_options()

In the Linux kernel, the following vulnerability has been resolved: ext4: fix string copying in parse_apply_sb_mount_options() strscpy_pad() can't be used to copy a non-NUL-term string into a NUL-term string of possibly bigger size. Commit 0efc5990bca5 ("string.h: Introduce memtostr() and memtostr_pad()") provides additional information in that regard. So if this happens, the following warning is observed: strnlen: detected buffer overflow: 65 byte read of buffer size 64 WARNING: CPU: 0 PID: 28655 at lib/string_helpers.c:1032 __fortify_report+0x96/0xc0 lib/string_helpers.c:1032 Modules linked in: CPU: 0 UID: 0 PID: 28655 Comm: syz-executor.3 Not tainted 6.12.54-syzkaller-00144-g5f0270f1ba00 #0 Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.16.3-debian-1.16.3-2 04/01/2014 RIP: 0010:__fortify_report+0x96/0xc0 lib/string_helpers.c:1032 Call Trace: <TASK> __fortify_panic+0x1f/0x30 lib/string_helpers.c:1039 strnlen include/linux/fortify-string.h:235 [inline] sized_strscpy include/linux/fortify-string.h:309 [inline] parse_apply_sb_mount_options fs/ext4/super.c:2504 [inline] __ext4_fill_super fs/ext4/super.c:5261 [inline] ext4_fill_super+0x3c35/0xad00 fs/ext4/super.c:5706 get_tree_bdev_flags+0x387/0x620 fs/super.c:1636 vfs_get_tree+0x93/0x380 fs/super.c:1814 do_new_mount fs/namespace.c:3553 [inline] path_mount+0x6ae/0x1f70 fs/namespace.c:3880 do_mount fs/namespace.c:3893 [inline] __do_sys_mount fs/namespace.c:4103 [inline] __se_sys_mount fs/namespace.c:4080 [inline] __x64_sys_mount+0x280/0x300 fs/namespace.c:4080 do_syscall_x64 arch/x86/entry/common.c:52 [inline] do_syscall_64+0x64/0x140 arch/x86/entry/common.c:83 entry_SYSCALL_64_after_hwframe+0x76/0x7e Since userspace is expected to provide s_mount_opts field to be at most 63 characters long with the ending byte being NUL-term, use a 64-byte buffer which matches the size of s_mount_opts, so that strscpy_pad() does its job properly. Return with error if the user still managed to provide a non-NUL-term string here. Found by Linux Verification Center (linuxtesting.org) with Syzkaller.

UnknownCVSS not scoredNot KEV-listedUpdated
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Glexia's TakeAutomated analysisunknown

Security readout for executives and security teams

Plain-English summary

This is a Linux kernel ext4 bug in mount option handling. A malformed, non-NUL-terminated mount option string can trigger a fortified string handling warning during ext4 mount processing. The public data does not provide CVSS, CWE, confirmed exploitation, or a clear business impact beyond the kernel warning path.

Executive priority

Treat as a kernel hygiene update, not an emergency, unless affected systems allow untrusted mount operations or are covered by vendor advisories. Prioritize normal kernel patch cycles and higher urgency for appliances or shared systems with delegated mount capability.

Technical view

The flaw is in ext4 parse_apply_sb_mount_options(). The source says strscpy_pad() was used incorrectly for a non-NUL-terminated source, causing strnlen to detect a 65-byte read of a 64-byte buffer. The fix uses a 64-byte buffer matching s_mount_opts and errors if input remains non-NUL-terminated.

Likely exposure

Exposure is limited to Linux systems running affected kernel builds with ext4 mount handling. Practical exposure depends on whether untrusted users or automation can influence mount requests or filesystem images. The supplied affected-version data is not enough to map every distribution package reliably.

Exploitation context

The issue was found by Linux Verification Center with Syzkaller. The bundle marks KEV as false and cites no active exploitation. The trace involves the mount syscall and ext4 superblock processing, but the sources do not establish remote exploitation or privilege escalation.

Researcher notes

Evidence supports a bounds/string-termination bug in ext4 mount option parsing. Impact is under-specified: no CVSS, CWE, exploit claim, or complete distro mapping is provided. Avoid assuming exploitability beyond the cited warning path without vendor or kernel maintainer analysis.

Mitigation direction

  • Update affected Linux kernels using vendor or upstream stable guidance.
  • Review distribution advisories for exact fixed package versions.
  • Limit mount privileges to trusted administrators and controlled automation.
  • Apply Siemens guidance where listed Siemens products are deployed.

Validation and detection

  • Inventory Linux kernel versions across servers, appliances, and embedded products.
  • Check whether ext4 filesystems and mount workflows are in use.
  • Compare installed kernels with vendor advisories and referenced stable commits.
  • Search kernel logs for related fortify or ext4 mount warnings.
Prepared
Confidence
medium
Sources
9

Public sources used

Generated from the cited source records. This long-tail analysis has not been individually reviewed by a named human.

Potential ATT&CK relevance

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CVE-2025-71123 mapping review

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Vulnerability profileCVE Program record
Severity
Unknown
CVSS
Not scored
Known Exploited
No
Published
Official CVE source material

CNA and ADP enrichment extracted from CVE v5

These fields come from the CVE record and ADP containers, not from Glexia's Take. They preserve time-varying source decisions such as CISA SSVC, KEV status, CVSS metrics, and provider references.

0CVSS vectors
3Timeline events
1ADP providers
8Source links

Vulnerability timeline

Timeline events are normalized from CVE metadata, CNA source timelines, ADP timelines, and KEV metadata when present.

  1. CVE reservedCVE Program

    The CVE ID was reserved by the assigning CNA.

  2. CVE publishedCVE Program

    The CVE record was published.

  3. CVE updatedCVE Program

    The CVE record metadata indicates this as the latest update time.

ADP provider summaries

siemens-SADPADP container

Source materials

Affected products

Products and packages named in the record

VendorProductVersion / packageStatus
LinuxLinuxb2bac84fde28fb6a88817b8b761abda17a1d300b, e651294218d2684302ee5ed95ccf381646f3e5b4, 01829af7656b56d83682b3491265d583d502e502, 2a0cf438320cdb783e0378570744c0ef0d83e934, 8ecb790ea8c3fc69e77bace57f14cf0d7c177bd8, 8ecb790ea8c3fc69e77bace57f14cf0d7c177bd8, 7bf46ff83a0ef11836e38ebd72cdc5107209342d, a6e94557cd05adc82fae0400f6e17745563e5412, 5.10.246, 6.1.158, 6.6.114, 6.12.54, 5.4.301, 6.17.4unaffected
LinuxLinux6.18, 0, 5.10.248, 6.1.160, 6.6.120, 6.12.64, 6.18.3, 6.19affected
Weakness

CWE details

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