GHSA-H7P4-FPXW-M265

Vulnerability from github – Published: 2026-04-22 15:31 – Updated: 2026-04-28 18:30
VLAI?
Details

In the Linux kernel, the following vulnerability has been resolved:

module: Fix kernel panic when a symbol st_shndx is out of bounds

The module loader doesn't check for bounds of the ELF section index in simplify_symbols():

   for (i = 1; i < symsec->sh_size / sizeof(Elf_Sym); i++) {
    const char *name = info->strtab + sym[i].st_name;

    switch (sym[i].st_shndx) {
    case SHN_COMMON:

    [...]

    default:
        /* Divert to percpu allocation if a percpu var. */
        if (sym[i].st_shndx == info->index.pcpu)
            secbase = (unsigned long)mod_percpu(mod);
        else

/ HERE --> / secbase = info->sechdrs[sym[i].st_shndx].sh_addr; sym[i].st_value += secbase; break; } }

A symbol with an out-of-bounds st_shndx value, for example 0xffff (known as SHN_XINDEX or SHN_HIRESERVE), may cause a kernel panic:

BUG: unable to handle page fault for address: ... RIP: 0010:simplify_symbols+0x2b2/0x480 ... Kernel panic - not syncing: Fatal exception

This can happen when module ELF is legitimately using SHN_XINDEX or when it is corrupted.

Add a bounds check in simplify_symbols() to validate that st_shndx is within the valid range before using it.

This issue was discovered due to a bug in llvm-objcopy, see relevant discussion for details [1].

[1] https://lore.kernel.org/linux-modules/20251224005752.201911-1-ihor.solodrai@linux.dev/

Severity ?
5.5 (Medium)
CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H
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{
  "affected": [],
  "aliases": [
    "CVE-2026-31521"
  ],
  "database_specific": {
    "cwe_ids": [
      "CWE-787"
    ],
    "github_reviewed": false,
    "github_reviewed_at": null,
    "nvd_published_at": "2026-04-22T14:16:51Z",
    "severity": "MODERATE"
  },
  "details": "In the Linux kernel, the following vulnerability has been resolved:\n\nmodule: Fix kernel panic when a symbol st_shndx is out of bounds\n\nThe module loader doesn\u0027t check for bounds of the ELF section index in\nsimplify_symbols():\n\n       for (i = 1; i \u003c symsec-\u003esh_size / sizeof(Elf_Sym); i++) {\n\t\tconst char *name = info-\u003estrtab + sym[i].st_name;\n\n\t\tswitch (sym[i].st_shndx) {\n\t\tcase SHN_COMMON:\n\n\t\t[...]\n\n\t\tdefault:\n\t\t\t/* Divert to percpu allocation if a percpu var. */\n\t\t\tif (sym[i].st_shndx == info-\u003eindex.pcpu)\n\t\t\t\tsecbase = (unsigned long)mod_percpu(mod);\n\t\t\telse\n  /** HERE --\u003e **/\t\tsecbase = info-\u003esechdrs[sym[i].st_shndx].sh_addr;\n\t\t\tsym[i].st_value += secbase;\n\t\t\tbreak;\n\t\t}\n\t}\n\nA symbol with an out-of-bounds st_shndx value, for example 0xffff\n(known as SHN_XINDEX or SHN_HIRESERVE), may cause a kernel panic:\n\n  BUG: unable to handle page fault for address: ...\n  RIP: 0010:simplify_symbols+0x2b2/0x480\n  ...\n  Kernel panic - not syncing: Fatal exception\n\nThis can happen when module ELF is legitimately using SHN_XINDEX or\nwhen it is corrupted.\n\nAdd a bounds check in simplify_symbols() to validate that st_shndx is\nwithin the valid range before using it.\n\nThis issue was discovered due to a bug in llvm-objcopy, see relevant\ndiscussion for details [1].\n\n[1] https://lore.kernel.org/linux-modules/20251224005752.201911-1-ihor.solodrai@linux.dev/",
  "id": "GHSA-h7p4-fpxw-m265",
  "modified": "2026-04-28T18:30:29Z",
  "published": "2026-04-22T15:31:43Z",
  "references": [
    {
      "type": "ADVISORY",
      "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-31521"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/082f15d2887329e0f43fd3727e69365f5bfe5d2c"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/4bbdb0e48176fd281c2b9a211b110db6fd94e175"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/5d16f519b6eb1d071807e57efe0df2baa8d32ad6"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/6ba6957c640f58dc8ef046981a045da43e47ea23"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/ec2b22a58073f80739013588af448ff6e2ab906f"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/ef75dc1401d8e797ee51559a0dd0336c225e1776"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/f9d69d5e7bde2295eb7488a56f094ac8f5383b92"
    }
  ],
  "schema_version": "1.4.0",
  "severity": [
    {
      "score": "CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H",
      "type": "CVSS_V3"
    }
  ]
}


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