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NVD / CVE Program· CNA Linux

CVE-2023-53143: ext4: fix another off-by-one fsmap error on 1k block filesystems

Noroxi assessment

Priority: Monitor (action score 22/100)

  • The sources we track (CISA KEV, Exploit-DB, Metasploit, Nuclei, GitHub) show no public exploit code or exploitation in the wild.
  • Probability of exploitation in the next 30 days: 0.19% (FIRST EPSS).
  • Someone with local access to the system can trigger it. A low-privileged account is enough. No user action is required. No special conditions are required; it is repeatable.
  • Fixed version: Linux Linux 15ebade3266b300da9cd1edce4004fe8fd6a2b88, 1d2366624b4c19a2ba6baf67fe57f4a1b0f67c05, a70b49dc7eee5dbe3775a650ce598e3557ff5475.

Low priority for now. Upgrade to Linux Linux 15ebade3266b300da9cd1edce4004fe8fd6a2b88, 1d2366624b4c19a2ba6baf67fe57f4a1b0f67c05, a70b49dc7eee5dbe3775a650ce598e3557ff5475 or later.

Generated automatically from the record's data: CVSS (NVD and CNA), CISA KEV and SSVC, FIRST EPSS, exploit sources, fixed versions. How we calculate it

Primary sources: NVD · CVE.org · FIRST EPSS

In the Linux kernel, the following vulnerability has been resolved: ext4: fix another off-by-one fsmap error on 1k block filesystems Apparently syzbot figured out that issuing this FSMAP call: struct fsmap_head cmd = { .fmh_count = ...; .fmh_keys = { { .fmr_device = /* ext4 dev */, .fmr_physical = 0, }, { .fmr_device = /* ext4 dev */, .fmr_physical = 0, }, }, ... }; ret = ioctl(fd, FS_IOC_GETFSMAP, &cmd); Produces this crash if the underlying filesystem is a 1k-block ext4 filesystem: kernel BUG at fs/ext4/ext4.h:3331! invalid opcode: 0000 [#1] PREEMPT SMP CPU: 3 PID: 3227965 Comm: xfs_io Tainted: G W O 6.2.0-rc8-achx Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.15.0-1 04/01/2014 RIP: 0010:ext4_mb_load_buddy_gfp+0x47c/0x570 [ext4] RSP: 0018:ffffc90007c03998 EFLAGS: 00010246 RAX: ffff888004978000 RBX: ffffc90007c03a20 RCX: ffff888041618000 RDX: 0000000000000000 RSI: 00000000000005a4 RDI: ffffffffa0c99b11 RBP: ffff888012330000 R08: ffffffffa0c2b7d0 R09: 0000000000000400 R10: ffffc90007c03950 R11: 0000000000000000 R12: 0000000000000001 R13: 00000000ffffffff R14: 0000000000000c40 R15: ffff88802678c398 FS: 00007fdf2020c880(0000) GS:ffff88807e100000(0000) knlGS:0000000000000000 CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 CR2: 00007ffd318a5fe8 CR3: 000000007f80f001 CR4: 00000000001706e0 Call Trace: <TASK> ext4_mballoc_query_range+0x4b/0x210 [ext4 dfa189daddffe8fecd3cdfd00564e0f265a8ab80] ext4_getfsmap_datadev+0x713/0x890 [ext4 dfa189daddffe8fecd3cdfd00564e0f265a8ab80] ext4_getfsmap+0x2b7/0x330 [ext4 dfa189daddffe8fecd3cdfd00564e0f265a8ab80] ext4_ioc_getfsmap+0x153/0x2b0 [ext4 dfa189daddffe8fecd3cdfd00564e0f265a8ab80] __ext4_ioctl+0x2a7/0x17e0 [ext4 dfa189daddffe8fecd3cdfd00564e0f265a8ab80] __x64_sys_ioctl+0x82/0xa0 do_syscall_64+0x2b/0x80 entry_SYSCALL_64_after_hwframe+0x46/0xb0 RIP: 0033:0x7fdf20558aff RSP: 002b:00007ffd318a9e30 EFLAGS: 00000246 ORIG_RAX: 0000000000000010 RAX: ffffffffffffffda RBX: 00000000000200c0 RCX: 00007fdf20558aff RDX: 00007fdf1feb2010 RSI: 00000000c0c0583b RDI: 0000000000000003 RBP: 00005625c0634be0 R08: 00005625c0634c40 R09: 0000000000000001 R10: 0000000000000000 R11: 0000000000000246 R12: 00007fdf1feb2010 R13: 00005625be70d994 R14: 0000000000000800 R15: 0000000000000000 For GETFSMAP calls, the caller selects a physical block device by writing its block number into fsmap_head.fmh_keys[01].fmr_device. To query mappings for a subrange of the device, the starting byte of the range is written to fsmap_head.fmh_keys[0].fmr_physical and the last byte of the range goes in fsmap_head.fmh_keys[1].fmr_physical. IOWs, to query what mappings overlap with bytes 3-14 of /dev/sda, you'd set the inputs as follows: fmh_keys[0] = { .fmr_device = major(8, 0), .fmr_physical = 3}, fmh_keys[1] = { .fmr_device = major(8, 0), .fmr_physical = 14}, Which would return you whatever is mapped in the 12 bytes starting at physical offset 3. The crash is due to insufficient range validation of keys[1] in ext4_getfsmap_datadev. On 1k-block filesystems, block 0 is not part of the filesystem, which means that s_first_data_block is nonzero. ext4_get_group_no_and_offset subtracts this quantity from the blocknr argument before cracking it into a group number and a block number within a group. IOWs, block group 0 spans blocks 1-8192 (1-based) instead of 0-8191 (0-based) like what happens with larger blocksizes. The net result of this encoding is that blocknr < s_first_data_block is not a valid input to this function. The end_fsb variable is set from the keys that are copied from userspace, which means that in the above example, its value is zero. That leads to an underflow here: blocknr = blocknr - le32_to_cpu(es->s_first_data_block); The division then operates on -1: offset = do_div(blocknr, EXT4_BLOCKS_PER_GROUP(sb)) >> EXT4_SB(sb)->s_cluster_bits; Leaving an impossibly large group number (2^32-1) in blocknr. ext4_getfsmap_check_keys checked that keys[0 ---truncated---

MediumCVSS 5.5 · v3.1—No exploit Fix available
Published
May 2, 2025
Updated
Jun 17, 2026
EPSS
0.1% · 9th percentile

Report tools

JSON

Action score

22

Monitor

Low priority for now.

CVSS
22 / 40 · 5.5 / 10
CISA KEV
0 / 30 · Not listed
EPSS
0 / 30 · 0.1%

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  • Not in KEV: no record of exploitation in the wild
  • No public exploit code on record
  • A fix has been released

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Noroxi analysis

What does it mean in your environment?

The assessment above is generated automatically from the record's data; it doesn't know your environment. Our team verifies on your systems whether this vulnerability is actually exploitable and which mitigation is enough.

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Affected systems

Is your version affected?

Pick the product and type the version you run. It's compared with this record's version ranges in your browser; the version isn't sent anywhere.

VendorProduct
linuxlinux kernel

Affected versions

NVD version ranges (for catalog products). Add the product to your stack with a version and matching uses these.

  • linux linux kernel4.13 and later · before 4.14.310
  • linux linux kernel4.15 and later · before 4.19.278
  • linux linux kernel4.20 and later · before 5.4.237
  • linux linux kernel5.5 and later · before 5.10.175
  • linux linux kernel5.11 and later · before 5.15.103
  • linux linux kernel5.16 and later · before 6.1.20
  • linux linux kernel6.2 and later · before 6.2.7
  • linux linux kernel6.3

Versions reported by the vendor

Affected version ranges reported by the assigning authority (Linux). Independent of NVD's CPE analysis and usually ahead of it.

  • Linux Linux

    • 4.13affected
    • 4a4956249dac0b9b0027949907bff0cd1a9b57fa and later · before a70b49dc7eee5dbe3775a650ce598e3557ff5475affected · git
    • 4a4956249dac0b9b0027949907bff0cd1a9b57fa and later · before f16054ac1774915160ca4e1c73ff7a269465a1b9affected · git
    • 4a4956249dac0b9b0027949907bff0cd1a9b57fa and later · before c24f838493792b5e78a3596b4ca96375aa0af4c2affected · git
    • 4a4956249dac0b9b0027949907bff0cd1a9b57fa and later · before 1d2366624b4c19a2ba6baf67fe57f4a1b0f67c05affected · git
    • 4a4956249dac0b9b0027949907bff0cd1a9b57fa and later · before c5d7c31e17224d847a330180ec1b03bf390632b2affected · git
    • 4a4956249dac0b9b0027949907bff0cd1a9b57fa and later · before eb3a695aa71a514f2e7f5778e05faba3733b70a0affected · git
    • 4a4956249dac0b9b0027949907bff0cd1a9b57fa and later · before 15ebade3266b300da9cd1edce4004fe8fd6a2b88affected · git
    • 4a4956249dac0b9b0027949907bff0cd1a9b57fa and later · before c993799baf9c5861f8df91beb80e1611b12efcbdaffected · git
    • before 4.13not affected · semver

Package-level exposure

OSV and GitHub Advisory data: ecosystem, package and range. SBOM matching uses this table.

EcosystemPackageAffected rangeFix
Debian:12linuxbefore 6.1.20-16.1.20-1

Same product

linux: all records

Other highest-scoring records for the same primary product.

  • CVE-2026-31431crypto: algif_aead - Revert to operating out-of-placeKEV
    90Now
  • CVE-2022-0847A flaw was found in the way the "flags" member of the new pipe buffer structure was lacking proper initialization in copy_page_to_iter_pipe KEV
    89Now
  • CVE-2021-22555Heap Out-Of-Bounds Write in Netfilter IP6T_SO_SET_REPLACEKEV
    85Now

Published before and after this one in the same product

  • ← EarlierCVE-2023-53140May 2, 2025 · scsi: core: Remove the /proc/scsi/${proc_name} directory earlier
    22Monitor
  • ← EarlierCVE-2023-53141May 2, 2025 · ila: do not generate empty messages in ila_xlat_nl_cmd_get_mapping()
    22Monitor
  • Later →CVE-2025-37798May 2, 2025 · codel: remove sch->q.qlen check before qdisc_tree_reduce_backlog()
    31Monitor

Remediation

Which version to upgrade to

Fix versions compiled from the vendor, package registries and Microsoft. Verify the vendor's note before upgrading.

Product / packageFixed versionSource
Linux Linux15ebade3266b300da9cd1edce4004fe8fd6a2b88Vendor (CNA)
Linux Linux1d2366624b4c19a2ba6baf67fe57f4a1b0f67c05Vendor (CNA)
Linux Linuxa70b49dc7eee5dbe3775a650ce598e3557ff5475Vendor (CNA)
Linux Linuxc24f838493792b5e78a3596b4ca96375aa0af4c2Vendor (CNA)
Linux Linuxc5d7c31e17224d847a330180ec1b03bf390632b2Vendor (CNA)
Linux Linuxc993799baf9c5861f8df91beb80e1611b12efcbdVendor (CNA)
Linux Linuxeb3a695aa71a514f2e7f5778e05faba3733b70a0Vendor (CNA)
Linux Linuxf16054ac1774915160ca4e1c73ff7a269465a1b9Vendor (CNA)
debian:linux6.1.20-1 · Debian:12Package registry (OSV)

Exploit status

No known public exploit

No public exploit has been observed yet. That doesn't mean you're safe, only that the bar is a little higher.

Research context

For pentesters and researchers: attack profile, score disagreement, timeline, patch commits, credits, variant and chain candidates, bug bounty scope. All derived from existing data; no exploit code.

Timeline

From publication to today: proof of concept, Metasploit module, CISA KEV and fix record. Dates are as reported by the sources.

No dated events beyond publication.

No history yet (it accumulates with the daily EPSS job).

Patch and commit links

Commit, PR and diff links among the references. A starting point for patch-diffing and variant hunting; fixes, not exploits.

No commit or PR link among the references.

Credits

All researchers

Finders, reporters and analysts named in the CNA record. Click a name for that researcher’s other records.

No credits in the CNA record.

Variant candidates

Same product, same weakness class, within 18 months. If the patch missed the root cause, the sibling bug is here.

  • CVE-2026-53088418 days apartnet: bcmgenet: fix off-by-one in bcmgenet_put_txcb
    39Monitor
  • CVE-2026-53309420 days apartocfs2/dlm: fix off-by-one in dlm_match_regions() region comparison
    39Monitor
  • CVE-2026-64047443 days apartnet: tls: fix off-by-one in sg_chain entry count for wrapped sk_msg ring
    39Monitor
  • CVE-2024-5799065 days apartwifi: mt76: mt7925: fix off by one in mt7925_load_clc()
    31Monitor
  • CVE-2024-47682193 days apartscsi: sd: Fix off-by-one error in sd_read_block_characteristics()
    31Monitor
  • CVE-2024-49880193 days apartext4: fix off by one issue in alloc_flex_gd()
    31Monitor

Chain candidates

An authentication bypass and a privilege-requiring bug in the same product, published close together: combined they may become an unauthenticated path.

—

Bug bounty scope

No known public program.

Source: bounty-targets-data (public HackerOne, Bugcrowd, Intigriti, YesWeHack listings).

Technical details

Attack conditions

  • Someone with local access to the system can trigger it.
  • A low-privileged account is enough.
  • No user action is required.
  • No special conditions are required; it is repeatable.

If successful

Confidentiality
none
Integrity
none
Availability
high · the service can be disrupted
Attack vector
Local
Attack complexity
Low
Privileges required
Low
User interaction
None
Scope
Unchanged
Confidentiality impact
None
Integrity impact
None
Availability impact
High

Weakness class (CWE)

CWE-193 · Off-by-one Error

CVSS vector

CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H

nvd-primary

Attack context

MITRE CAPEC attack patterns and ATT&CK techniques for this weakness class (CWE). A starting point for detection rules and threat hunting.

MITRE has no CAPEC/ATT&CK mapping for this CWE.

Change log

  1. Fix✗ → ✓

For records you follow, these changes also arrive as notifications. →

References

Show all references (7 more)

Vendor advisories and official records. Exploit/PoC links are deliberately left out.

All records