CVE-2026-98127 (GCVE-0-2026-98127)

Vulnerability from cvelistv5 – Published: 2026-09-25 10:36 – Updated: 2026-09-25 10:36
VLAI
Title
smb/client: validate new EOF for insert range
Summary
In the Linux kernel, the following vulnerability has been resolved: smb/client: validate new EOF for insert range smb3_insert_range() does not check if the new file size (i_size + len) is valid. This allows FALLOC_FL_INSERT_RANGE to bypass RLIMIT_FSIZE, exceed s_maxbytes, or produce a size outside the loff_t range. Use check_add_overflow() to calculate the new EOF. Validate it with inode_newsize_ok() before modifying the file. Reproducer, using a file on a CIFS mount: bash -c ' FILE=/mnt/cifs/repro trap "" SIGXFSZ ulimit -f 3072 # RLIMIT_FSIZE = 3 MiB # A regular write is stopped at 3 MiB. dd if=/dev/zero of="$FILE" bs=1M count=4 status=none stat -c "size after write: %s" "$FILE" # Insert 2 MiB into a 2 MiB file. truncate -s 2M "$FILE" fallocate -i -o 0 -l 2M "$FILE" stat -c "size after insert: %s" "$FILE" ' Before this change, the regular write stops at the 3 MiB limit, but insert range grows the file to 4 MiB: dd: error writing '/mnt/cifs/repro': File too large size after write: 3145728 size after insert: 4194304 After this change, insert range also fails at the limit and leaves the 2 MiB file unchanged: dd: error writing '/mnt/cifs/repro': File too large size after write: 3145728 fallocate: fallocate failed: File too large size after insert: 2097152
Severity
No CVSS data available.
Assigner
References
Impacted products
Vendor Product Version CPE status
Linux Linux Affected: 7fe6fe95b936084dce6eedcc2cccadf96eafae73 , < 7c2c69045aa76ccaa7f16f1478eb312130ce4951 (git)
Affected: 7fe6fe95b936084dce6eedcc2cccadf96eafae73 , < bc7602b9082ef195d913c4c16fa9853dd262333e (git)
Affected: 7fe6fe95b936084dce6eedcc2cccadf96eafae73 , < f8cbfe3a3fcee7d991fd223f660f3e5df13221cf (git)
Affected: 7fe6fe95b936084dce6eedcc2cccadf96eafae73 , < 1519dc88c87f5346dae0464d7d6da1b6bf1f6e8e (git)
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Linux Linux Affected: 5.13
Unaffected: 0 , < 5.13 (semver)
Unaffected: 6.12.111 , ≤ 6.12.* (semver)
Unaffected: 6.18.53 , ≤ 6.18.* (semver)
Unaffected: 7.2.7 , ≤ 7.2.* (semver)
Unaffected: 7.3-rc2 , ≤ * (original_commit_for_fix)
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          "programFiles": [
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          "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nsmb/client: validate new EOF for insert range\n\nsmb3_insert_range() does not check if the new file size\n(i_size + len) is valid. This allows FALLOC_FL_INSERT_RANGE to bypass\nRLIMIT_FSIZE, exceed s_maxbytes, or produce a size outside the loff_t\nrange.\n\nUse check_add_overflow() to calculate the new EOF. Validate it with\ninode_newsize_ok() before modifying the file.\n\nReproducer, using a file on a CIFS mount:\n\n\tbash -c \u0027\n\t\tFILE=/mnt/cifs/repro\n\n\t\ttrap \"\" SIGXFSZ\n\t\tulimit -f 3072\t\t# RLIMIT_FSIZE = 3 MiB\n\n\t\t# A regular write is stopped at 3 MiB.\n\t\tdd if=/dev/zero of=\"$FILE\" bs=1M count=4 status=none\n\t\tstat -c \"size after write: %s\" \"$FILE\"\n\n\t\t# Insert 2 MiB into a 2 MiB file.\n\t\ttruncate -s 2M \"$FILE\"\n\t\tfallocate -i -o 0 -l 2M \"$FILE\"\n\t\tstat -c \"size after insert: %s\" \"$FILE\"\n\t\u0027\n\nBefore this change, the regular write stops at the 3 MiB limit, but\ninsert range grows the file to 4 MiB:\n\n\tdd: error writing \u0027/mnt/cifs/repro\u0027: File too large\n\tsize after write: 3145728\n\tsize after insert: 4194304\n\nAfter this change, insert range also fails at the limit and leaves the\n2 MiB file unchanged:\n\n\tdd: error writing \u0027/mnt/cifs/repro\u0027: File too large\n\tsize after write: 3145728\n\tfallocate: fallocate failed: File too large\n\tsize after insert: 2097152"
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          "url": "https://git.kernel.org/stable/c/1519dc88c87f5346dae0464d7d6da1b6bf1f6e8e"
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      "title": "smb/client: validate new EOF for insert range",
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    "cveId": "CVE-2026-98127",
    "datePublished": "2026-09-25T10:36:08.406Z",
    "dateReserved": "2026-09-25T10:25:14.318Z",
    "dateUpdated": "2026-09-25T10:36:08.406Z",
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            "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nsmb/client: validate new EOF for insert range\n\nsmb3_insert_range() does not check if the new file size\n(i_size + len) is valid. This allows FALLOC_FL_INSERT_RANGE to bypass\nRLIMIT_FSIZE, exceed s_maxbytes, or produce a size outside the loff_t\nrange.\n\nUse check_add_overflow() to calculate the new EOF. Validate it with\ninode_newsize_ok() before modifying the file.\n\nReproducer, using a file on a CIFS mount:\n\n\tbash -c \u0027\n\t\tFILE=/mnt/cifs/repro\n\n\t\ttrap \"\" SIGXFSZ\n\t\tulimit -f 3072\t\t# RLIMIT_FSIZE = 3 MiB\n\n\t\t# A regular write is stopped at 3 MiB.\n\t\tdd if=/dev/zero of=\"$FILE\" bs=1M count=4 status=none\n\t\tstat -c \"size after write: %s\" \"$FILE\"\n\n\t\t# Insert 2 MiB into a 2 MiB file.\n\t\ttruncate -s 2M \"$FILE\"\n\t\tfallocate -i -o 0 -l 2M \"$FILE\"\n\t\tstat -c \"size after insert: %s\" \"$FILE\"\n\t\u0027\n\nBefore this change, the regular write stops at the 3 MiB limit, but\ninsert range grows the file to 4 MiB:\n\n\tdd: error writing \u0027/mnt/cifs/repro\u0027: File too large\n\tsize after write: 3145728\n\tsize after insert: 4194304\n\nAfter this change, insert range also fails at the limit and leaves the\n2 MiB file unchanged:\n\n\tdd: error writing \u0027/mnt/cifs/repro\u0027: File too large\n\tsize after write: 3145728\n\tfallocate: fallocate failed: File too large\n\tsize after insert: 2097152"
          }
        ],
        "id": "CVE-2026-98127",
        "lastModified": "2026-09-25T11:17:44.050",
        "metrics": {},
        "published": "2026-09-25T11:17:44.050",
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        "vulnStatus": "Received"
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    "suse_vex": {
      "aggregate_severity": "not set",
      "current_release_date": "2026-09-25T23:46:28Z",
      "cve": "CVE-2026-98127",
      "id": "CVE-2026-98127",
      "initial_release_date": "2026-09-25T23:46:28Z",
      "source": "SUSE CSAF VEX",
      "status": "interim",
      "title": "SUSE CVE CVE-2026-98127",
      "url": "https://ftp.suse.com/pub/projects/security/csaf-vex/cve-2026-98127.json",
      "version": "2"
    }
  }
}



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Forecast uses a logistic model when the trend is rising, or an exponential decay model when the trend is falling. Fitted via linearized least squares.

Sightings

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  • Seen: The vulnerability was mentioned, discussed, or observed by the user.
  • 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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  • Not patched: The vulnerability was not observed as successfully patched by the user who reported the sighting.



Related by attack behaviour

Vulnerabilities whose description is nearest to this one in the vector space of the CIRCL/vulnerability-attack-technique-biencoder model. This is a similarity search over the bi-encoder space (plain cosine), not a classification, and it has no measured accuracy.