High

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.

Published Jan 14, 2026 · Updated Oct 14, 2026 · Sources: NIST National Vulnerability Database, CVE Program (cve.org) e CISA ADP, GitHub Security Advisories · CNA: Linux

Low

Who exploits it and how urgent it is

A 0–100 score combining confirmed exploitation, ransomware and APT use, public exploits, EPSS and severity.

No exploitation signal in the sources consulted so far.

How the score was calculated

EPSS 0.2% (30-day exploitation probability)+1
Technical severity (high)+6

The score orders the patch queue; it does not replace your asset context (internet exposure, criticality, compensating controls).

Triage

Is it exploited, how likely is exploitation, what does it touch, and how severe do the sources call it.

Exploitation

Not confirmed

Not in CISA KEV — an absence of record, not proof it is unexploited.

EPSS FIRST

0.17%

ahead of 6% of scored CVEs · Oct 15, 2026

Affects

Linux

Linux and 1 more

CVSS base

7.8

High · 2 source(s)

Remediation

Fixes and mitigations documented by the sources — linked to the original advisory.

Documented patch — git.kernel.org (NIST National Vulnerability Database)
Documented patch — git.kernel.org (NIST National Vulnerability Database)
Documented patch — git.kernel.org (NIST National Vulnerability Database)
Documented patch — git.kernel.org (NIST National Vulnerability Database)
Documented patch — git.kernel.org (NIST National Vulnerability Database)
Documented patch — git.kernel.org (NIST National Vulnerability Database)

First 24 hours

Ordered from the record’s own fields — exposure first, because you cannot patch what you have not found. A rule-generated starting point.

Identify exposed assets running the affected vendor/product/version combinations (Linux Linux, Linux Linux Kernel).
Apply the fixed version or the patch documented under Remediation.
Search available logs for exploit probes, errors and authentication anomalies.

Affected scope

Vendor, product and versions as the sources word them.

Vendor	Product	Versions	Status	Source
Linux	Linux	version 6.18≥ 6.17.4 and < 6.18≥ 5.4.301 and < 5.5≥ 6.12.54 and < 6.12.64≥ 6.6.114 and < 6.6.120≥ 6.1.158 and < 6.1.160≥ 5.10.246 and < 5.10.248version a6e94557cd05adc82fae0400f6e17745563e5412 and 7 more version 7bf46ff83a0ef11836e38ebd72cdc5107209342d≥ 8ecb790ea8c3fc69e77bace57f14cf0d7c177bd8 and < ee5a977b4e771cc181f39d504426dbd31ed701cc≥ 8ecb790ea8c3fc69e77bace57f14cf0d7c177bd8 and < 5bbacbbf1ca4419861dca3c6b82707c10e9c021c≥ 2a0cf438320cdb783e0378570744c0ef0d83e934 and < db9ee13fab0267eccf6544ee35b16c9522db9aac≥ 01829af7656b56d83682b3491265d583d502e502 and < 902ca2356f1e3ec5355c5808ad5d3f9d0095b0cc≥ e651294218d2684302ee5ed95ccf381646f3e5b4 and < 6e37143560e37869d51b7d9e0ac61fc48895f8a0≥ b2bac84fde28fb6a88817b8b761abda17a1d300b and < 52ac96c4a2dd7bc47666000440b0602d9742e820	Vulnerable	CVE Program (cve.org) e CISA ADP
Linux	Linux Kernel	version 6.19-rc8≥ 5.4.301 and < 5.5version 6.19-rc7version 6.19-rc6version 6.19-rc5version 6.19-rc4version 6.19-rc3version 6.19-rc2 and 8 more version 6.19-rc1version 6.18≥ 6.18.1 and < 6.18.3≥ 6.17.4 and < 6.18≥ 6.12.54 and < 6.12.64≥ 6.6.114 and < 6.6.120≥ 6.1.158 and < 6.1.160≥ 5.10.246 and < 5.10.248	Vulnerable	NIST National Vulnerability Database

Attack characteristics

The CVSS vector, decoded. It describes the attack, not your exposure to it.

Attack vector

Local

Attack complexity

Low

Privileges required

Low

User interaction

None

Scope

Unchanged

Confidentiality

High

Integrity

High

Availability

High

Every base score collected

Sources score independently and may disagree; each row says who scored it and under which version.

Score	Version	Severity	Expl.	Impact	Scored by
7.8	CVSS 3.1	High	1.8	5.9	nvd@nist.gov via NIST National Vulnerability Database
7.8	CVSS 3.1	High	—	—	GitHub, Inc. via GitHub Security Advisories

CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H (score shown at the top: nvd@nist.gov)

EPSS over time FIRST

Oct 13, 2026 → Oct 15, 2026 · 3 reading(s) · max 0.17%

Detection

Read off the CVSS vector and the weakness class. Starting points, not tested rules.

Local/physical vector: focus on endpoint telemetry (EDR) from affected hosts.

endpoint telemetry (EDR)

Timeline

What happened to this CVE, newest first.

2026
Affected products added · linux/linux
Oct 13, 2026 · CVE Program (cve.org) e CISA ADP
Record published
Oct 13, 2026
Fix documented
Oct 13, 2026 · NIST National Vulnerability Database
CVSS changed · 7.8
Oct 13, 2026 · NIST National Vulnerability Database
Source status changed · → Modified
Oct 13, 2026 · NIST National Vulnerability Database
Record created in this database
Oct 13, 2026 · NIST National Vulnerability Database
CVE published
Jan 14, 2026 · Linux

Source activity

Repeated readings are counted rather than listed.

2× References added · Oct 14, 2026 – Oct 14, 2026
1× Official description updated · Oct 13, 2026 – Oct 13, 2026

References

10 on the record

git.kernel.org/stable/c/ee5a977b4e771cc181f39d504426dbd31ed701cc
Patch, NIST National Vulnerability Database
git.kernel.org/stable/c/6e37143560e37869d51b7d9e0ac61fc48895f8a0
Patch, NIST National Vulnerability Database
git.kernel.org/stable/c/52ac96c4a2dd7bc47666000440b0602d9742e820
Patch, NIST National Vulnerability Database
git.kernel.org/stable/c/5bbacbbf1ca4419861dca3c6b82707c10e9c021c
Patch, NIST National Vulnerability Database
git.kernel.org/stable/c/902ca2356f1e3ec5355c5808ad5d3f9d0095b0cc
Patch, NIST National Vulnerability Database
git.kernel.org/stable/c/db9ee13fab0267eccf6544ee35b16c9522db9aac
Patch, NIST National Vulnerability Database
nvd.nist.gov/vuln/detail/CVE-2025-71123
GitHub Security Advisories
cert-portal.siemens.com/productcert/html/ssa-457936.html
NIST National Vulnerability Database
github.com/advisories/GHSA-mcqf-m32c-3xwp
GitHub Security Advisories
cert-portal.siemens.com/productcert/html/ssa-019113.html
NIST National Vulnerability Database

Elsewhere on this site

Linux
every CVE for this vendor

Related CVEs (same products)

Critical CVE-2026-99999 ipv4: validate checksum_start before completing checksum 16h
Unknown CVE-2026-98432 ipv4: free inet_opt and ireq_opt after an RCU grace period 16h
Unknown CVE-2026-98424 wifi: cfg80211: undo netns switch if renaming the wiphy fails 1d
Unknown CVE-2026-98425 wifi: mac80211: don't warn when an IBSS has no channel to scan 1d
Unknown CVE-2026-98426 wifi: mwifiex: fix IRQ leak using wrong index in MSI-X error path 1d
Unknown CVE-2026-98427 net/sched: codel: bound the dropping loop per dequeue call 1d

Not in any source we poll

Listed rather than left blank: an empty field and an unmeasured one look identical on screen, and only one is a reason to look elsewhere.

No CISA SSVC assessment.
No CWE classification.
No confirmed IOCs, IP addresses, domains, file hashes, or malware artifacts supplied.
No organization-specific asset inventory, compensating-control status, or patch deployment evidence supplied.
No exploit packet captures, log samples, or incident case IDs supplied.

Answered from this record

Text assembled only from the fields above — no additional claims.

What should defenders know first?

CVE-2025-71123 is "ext4: fix string copying in parse_apply_sb_mount_options()", rated High. It affects Linux (Linux); versions are in the scope table. It is not in CISA KEV, which does not rule out exploitation. CVSS 7.8 describes technical severity. EPSS 0.17% estimates the probability of exploitation in 30 days; neither replaces your asset context. First verify whether exposed or business-critical assets run the affected versions, apply vendor fixes or mitigations, and preserve logs for review.

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