CVE-2025-71123 (GCVE-0-2025-71123)

Vulnerability from cvelistv5 – Published: 2026-01-14 15:06 – Updated: 2026-01-14 15:06
VLAI?
Title
ext4: fix string copying in parse_apply_sb_mount_options()
Summary
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.
Severity ?
No CVSS data available.
Assigner
References
Impacted products
Vendor Product Version
Linux Linux Affected: e651294218d2684302ee5ed95ccf381646f3e5b4 , < 6e37143560e37869d51b7d9e0ac61fc48895f8a0 (git)
Affected: 01829af7656b56d83682b3491265d583d502e502 , < 902ca2356f1e3ec5355c5808ad5d3f9d0095b0cc (git)
Affected: 2a0cf438320cdb783e0378570744c0ef0d83e934 , < db9ee13fab0267eccf6544ee35b16c9522db9aac (git)
Affected: 8ecb790ea8c3fc69e77bace57f14cf0d7c177bd8 , < 5bbacbbf1ca4419861dca3c6b82707c10e9c021c (git)
Affected: 8ecb790ea8c3fc69e77bace57f14cf0d7c177bd8 , < ee5a977b4e771cc181f39d504426dbd31ed701cc (git)
Affected: 7bf46ff83a0ef11836e38ebd72cdc5107209342d (git)
Affected: b2bac84fde28fb6a88817b8b761abda17a1d300b (git)
Affected: a6e94557cd05adc82fae0400f6e17745563e5412 (git)
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    Linux Linux Affected: 6.18
Unaffected: 0 , < 6.18 (semver)
Unaffected: 6.1.160 , ≤ 6.1.* (semver)
Unaffected: 6.6.120 , ≤ 6.6.* (semver)
Unaffected: 6.12.64 , ≤ 6.12.* (semver)
Unaffected: 6.18.3 , ≤ 6.18.* (semver)
Unaffected: 6.19-rc1 , ≤ * (original_commit_for_fix)
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{
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          "value": "In the Linux kernel, the following vulnerability has been resolved:\n\next4: fix string copying in parse_apply_sb_mount_options()\n\nstrscpy_pad() can\u0027t be used to copy a non-NUL-term string into a NUL-term\nstring of possibly bigger size.  Commit 0efc5990bca5 (\"string.h: Introduce\nmemtostr() and memtostr_pad()\") provides additional information in that\nregard.  So if this happens, the following warning is observed:\n\nstrnlen: detected buffer overflow: 65 byte read of buffer size 64\nWARNING: CPU: 0 PID: 28655 at lib/string_helpers.c:1032 __fortify_report+0x96/0xc0 lib/string_helpers.c:1032\nModules linked in:\nCPU: 0 UID: 0 PID: 28655 Comm: syz-executor.3 Not tainted 6.12.54-syzkaller-00144-g5f0270f1ba00 #0\nHardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.16.3-debian-1.16.3-2 04/01/2014\nRIP: 0010:__fortify_report+0x96/0xc0 lib/string_helpers.c:1032\nCall Trace:\n \u003cTASK\u003e\n __fortify_panic+0x1f/0x30 lib/string_helpers.c:1039\n strnlen include/linux/fortify-string.h:235 [inline]\n sized_strscpy include/linux/fortify-string.h:309 [inline]\n parse_apply_sb_mount_options fs/ext4/super.c:2504 [inline]\n __ext4_fill_super fs/ext4/super.c:5261 [inline]\n ext4_fill_super+0x3c35/0xad00 fs/ext4/super.c:5706\n get_tree_bdev_flags+0x387/0x620 fs/super.c:1636\n vfs_get_tree+0x93/0x380 fs/super.c:1814\n do_new_mount fs/namespace.c:3553 [inline]\n path_mount+0x6ae/0x1f70 fs/namespace.c:3880\n do_mount fs/namespace.c:3893 [inline]\n __do_sys_mount fs/namespace.c:4103 [inline]\n __se_sys_mount fs/namespace.c:4080 [inline]\n __x64_sys_mount+0x280/0x300 fs/namespace.c:4080\n do_syscall_x64 arch/x86/entry/common.c:52 [inline]\n do_syscall_64+0x64/0x140 arch/x86/entry/common.c:83\n entry_SYSCALL_64_after_hwframe+0x76/0x7e\n\nSince userspace is expected to provide s_mount_opts field to be at most 63\ncharacters long with the ending byte being NUL-term, use a 64-byte buffer\nwhich matches the size of s_mount_opts, so that strscpy_pad() does its job\nproperly.  Return with error if the user still managed to provide a\nnon-NUL-term string here.\n\nFound by Linux Verification Center (linuxtesting.org) with Syzkaller."
        }
      ],
      "providerMetadata": {
        "dateUpdated": "2026-01-14T15:06:09.246Z",
        "orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
        "shortName": "Linux"
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          "url": "https://git.kernel.org/stable/c/ee5a977b4e771cc181f39d504426dbd31ed701cc"
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    "assignerShortName": "Linux",
    "cveId": "CVE-2025-71123",
    "datePublished": "2026-01-14T15:06:09.246Z",
    "dateReserved": "2026-01-13T15:30:19.654Z",
    "dateUpdated": "2026-01-14T15:06:09.246Z",
    "state": "PUBLISHED"
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  "vulnerability-lookup:meta": {
    "nvd": "{\"cve\":{\"id\":\"CVE-2025-71123\",\"sourceIdentifier\":\"416baaa9-dc9f-4396-8d5f-8c081fb06d67\",\"published\":\"2026-01-14T15:16:02.000\",\"lastModified\":\"2026-01-14T16:25:12.057\",\"vulnStatus\":\"Awaiting Analysis\",\"cveTags\":[],\"descriptions\":[{\"lang\":\"en\",\"value\":\"In the Linux kernel, the following vulnerability has been resolved:\\n\\next4: fix string copying in parse_apply_sb_mount_options()\\n\\nstrscpy_pad() can\u0027t be used to copy a non-NUL-term string into a NUL-term\\nstring of possibly bigger size.  Commit 0efc5990bca5 (\\\"string.h: Introduce\\nmemtostr() and memtostr_pad()\\\") provides additional information in that\\nregard.  So if this happens, the following warning is observed:\\n\\nstrnlen: detected buffer overflow: 65 byte read of buffer size 64\\nWARNING: CPU: 0 PID: 28655 at lib/string_helpers.c:1032 __fortify_report+0x96/0xc0 lib/string_helpers.c:1032\\nModules linked in:\\nCPU: 0 UID: 0 PID: 28655 Comm: syz-executor.3 Not tainted 6.12.54-syzkaller-00144-g5f0270f1ba00 #0\\nHardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.16.3-debian-1.16.3-2 04/01/2014\\nRIP: 0010:__fortify_report+0x96/0xc0 lib/string_helpers.c:1032\\nCall Trace:\\n \u003cTASK\u003e\\n __fortify_panic+0x1f/0x30 lib/string_helpers.c:1039\\n strnlen include/linux/fortify-string.h:235 [inline]\\n sized_strscpy include/linux/fortify-string.h:309 [inline]\\n parse_apply_sb_mount_options fs/ext4/super.c:2504 [inline]\\n __ext4_fill_super fs/ext4/super.c:5261 [inline]\\n ext4_fill_super+0x3c35/0xad00 fs/ext4/super.c:5706\\n get_tree_bdev_flags+0x387/0x620 fs/super.c:1636\\n vfs_get_tree+0x93/0x380 fs/super.c:1814\\n do_new_mount fs/namespace.c:3553 [inline]\\n path_mount+0x6ae/0x1f70 fs/namespace.c:3880\\n do_mount fs/namespace.c:3893 [inline]\\n __do_sys_mount fs/namespace.c:4103 [inline]\\n __se_sys_mount fs/namespace.c:4080 [inline]\\n __x64_sys_mount+0x280/0x300 fs/namespace.c:4080\\n do_syscall_x64 arch/x86/entry/common.c:52 [inline]\\n do_syscall_64+0x64/0x140 arch/x86/entry/common.c:83\\n entry_SYSCALL_64_after_hwframe+0x76/0x7e\\n\\nSince userspace is expected to provide s_mount_opts field to be at most 63\\ncharacters long with the ending byte being NUL-term, use a 64-byte buffer\\nwhich matches the size of s_mount_opts, so that strscpy_pad() does its job\\nproperly.  Return with error if the user still managed to provide a\\nnon-NUL-term string here.\\n\\nFound by Linux Verification Center (linuxtesting.org) with Syzkaller.\"}],\"metrics\":{},\"references\":[{\"url\":\"https://git.kernel.org/stable/c/5bbacbbf1ca4419861dca3c6b82707c10e9c021c\",\"source\":\"416baaa9-dc9f-4396-8d5f-8c081fb06d67\"},{\"url\":\"https://git.kernel.org/stable/c/6e37143560e37869d51b7d9e0ac61fc48895f8a0\",\"source\":\"416baaa9-dc9f-4396-8d5f-8c081fb06d67\"},{\"url\":\"https://git.kernel.org/stable/c/902ca2356f1e3ec5355c5808ad5d3f9d0095b0cc\",\"source\":\"416baaa9-dc9f-4396-8d5f-8c081fb06d67\"},{\"url\":\"https://git.kernel.org/stable/c/db9ee13fab0267eccf6544ee35b16c9522db9aac\",\"source\":\"416baaa9-dc9f-4396-8d5f-8c081fb06d67\"},{\"url\":\"https://git.kernel.org/stable/c/ee5a977b4e771cc181f39d504426dbd31ed701cc\",\"source\":\"416baaa9-dc9f-4396-8d5f-8c081fb06d67\"}]}}"
  }
}


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  • Confirmed: The vulnerability has been validated from an analyst's perspective.
  • Published Proof of Concept: A public proof of concept is available for this vulnerability.
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