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CVE-2023-53503

Full vulnerability record from the local CVENow database.

Description

In the Linux kernel, the following vulnerability has been resolved: ext4: allow ext4_get_group_info() to fail Previously, ext4_get_group_info() would treat an invalid group number as BUG(), since in theory it should never happen. However, if a malicious attaker (or fuzzer) modifies the superblock via the block device while it is the file system is mounted, it is possible for s_first_data_block to get set to a very large number. In that case, when calculating the block group of some block number (such as the starting block of a preallocation region), could result in an underflow and very large block group number. Then the BUG_ON check in ext4_get_group_info() would fire, resutling in a denial of service attack that can be triggered by root or someone with write access to the block device. For a quality of implementation perspective, it's best that even if the system administrator does something that they shouldn't, that it will not trigger a BUG. So instead of BUG'ing, ext4_get_group_info() will call ext4_error and return NULL. We also add fallback code in all of the callers of ext4_get_group_info() that it might NULL. Also, since ext4_get_group_info() was already borderline to be an inline function, un-inline it. The results in a next reduction of the compiled text size of ext4 by roughly 2k.

Severity
MEDIUM
CVSS score
5.5 (v3.1)
Vulnerability status
Analyzed
Source identifier
416baaa9-dc9f-4396-8d5f-8c081fb06d67
Published
2025-10-01 12:15:53.917000
Last modified
2026-11-05 21:17:23.370000
View original CVE JSON 
{
  "id": "CVE-2023-53503",
  "sourceIdentifier": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
  "published": "2025-10-01T12:15:53.917",
  "lastModified": "2026-11-05T21:17:23.370",
  "vulnStatus": "Analyzed",
  "cveTags": [],
  "descriptions": [
    {
      "lang": "en",
      "value": "In the Linux kernel, the following vulnerability has been resolved:\n\next4: allow ext4_get_group_info() to fail\n\nPreviously, ext4_get_group_info() would treat an invalid group number\nas BUG(), since in theory it should never happen.  However, if a\nmalicious attaker (or fuzzer) modifies the superblock via the block\ndevice while it is the file system is mounted, it is possible for\ns_first_data_block to get set to a very large number.  In that case,\nwhen calculating the block group of some block number (such as the\nstarting block of a preallocation region), could result in an\nunderflow and very large block group number.  Then the BUG_ON check in\next4_get_group_info() would fire, resutling in a denial of service\nattack that can be triggered by root or someone with write access to\nthe block device.\n\nFor a quality of implementation perspective, it's best that even if\nthe system administrator does something that they shouldn't, that it\nwill not trigger a BUG.  So instead of BUG'ing, ext4_get_group_info()\nwill call ext4_error and return NULL.  We also add fallback code in\nall of the callers of ext4_get_group_info() that it might NULL.\n\nAlso, since ext4_get_group_info() was already borderline to be an\ninline function, un-inline it.  The results in a next reduction of the\ncompiled text size of ext4 by roughly 2k."
    }
  ],
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            "fs/ext4/ext4.h",
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            "fs/ext4/mballoc.c",
            "fs/ext4/super.c"
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              "versionType": "original_commit_for_fix",
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  "metrics": {
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          "baseSeverity": "MEDIUM",
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          "attackComplexity": "LOW",
          "privilegesRequired": "LOW",
          "userInteraction": "NONE",
          "scope": "UNCHANGED",
          "confidentialityImpact": "NONE",
          "integrityImpact": "NONE",
          "availabilityImpact": "HIGH"
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          "role": "CISA Coordinator",
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  "weaknesses": [
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      "source": "[email protected]",
      "type": "Primary",
      "description": [
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          "value": "CWE-476"
        }
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    }
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}