{"id":"CVE-2026-31521","title":"module: Fix kernel panic when a symbol st_shndx is out of bounds","summary":"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't check for bounds of the ELF section index in\nsimplify_symbols():\n\n       for…","severity":"none","vendor":"Linux","product":"Linux","affected":["Linux >= 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 < 5d16f519b6eb1d071807e57efe0df2baa8d32ad6","Linux >= 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 < 4bbdb0e48176fd281c2b9a211b110db6fd94e175","Linux >= 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 < 082f15d2887329e0f43fd3727e69365f5bfe5d2c","Linux >= 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 < ec2b22a58073f80739013588af448ff6e2ab906f","Linux >= 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 < ef75dc1401d8e797ee51559a0dd0336c225e1776","Linux >= 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 < 6ba6957c640f58dc8ef046981a045da43e47ea23","Linux >= 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 < f9d69d5e7bde2295eb7488a56f094ac8f5383b92","Linux 2.6.12"],"published":"2026-04-22","updated":"2026-09-08","sourceUpdated":"2026-09-08T08:47:38.796Z","source":"CVEORG","sourceUrl":"https://www.cve.org/CVERecord?id=CVE-2026-31521","references":[{"url":"https://git.kernel.org/stable/c/5d16f519b6eb1d071807e57efe0df2baa8d32ad6"},{"url":"https://git.kernel.org/stable/c/4bbdb0e48176fd281c2b9a211b110db6fd94e175"},{"url":"https://git.kernel.org/stable/c/082f15d2887329e0f43fd3727e69365f5bfe5d2c"},{"url":"https://git.kernel.org/stable/c/ec2b22a58073f80739013588af448ff6e2ab906f"},{"url":"https://git.kernel.org/stable/c/ef75dc1401d8e797ee51559a0dd0336c225e1776"},{"url":"https://git.kernel.org/stable/c/6ba6957c640f58dc8ef046981a045da43e47ea23"},{"url":"https://git.kernel.org/stable/c/f9d69d5e7bde2295eb7488a56f094ac8f5383b92"}],"tags":["cve.org"],"epss":0.00166,"epssPercentile":0.05204,"ingestedAt":"2026-09-08T15:33:26.990Z","slug":"CVE-2026-31521","body":"## Overview\n\nIn 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't check for bounds of the ELF section index in\nsimplify_symbols():\n\n       for (i = 1; i < symsec->sh_size / sizeof(Elf_Sym); i++) {\n\t\tconst char *name = info->strtab + 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->index.pcpu)\n\t\t\t\tsecbase = (unsigned long)mod_percpu(mod);\n\t\t\telse\n  /** HERE --> **/\t\tsecbase = info->sechdrs[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/\n\n## Affected\n\n- `Linux >= 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 < 5d16f519b6eb1d071807e57efe0df2baa8d32ad6`\n- `Linux >= 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 < 4bbdb0e48176fd281c2b9a211b110db6fd94e175`\n- `Linux >= 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 < 082f15d2887329e0f43fd3727e69365f5bfe5d2c`\n- `Linux >= 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 < ec2b22a58073f80739013588af448ff6e2ab906f`\n- `Linux >= 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 < ef75dc1401d8e797ee51559a0dd0336c225e1776`\n- `Linux >= 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 < 6ba6957c640f58dc8ef046981a045da43e47ea23`\n- `Linux >= 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 < f9d69d5e7bde2295eb7488a56f094ac8f5383b92`\n- `Linux 2.6.12`\n\n## Remediation\n\nRefer to the linked advisories for vendor-supplied fixes and affected version ranges.","depth":"sunlit","depthScore":3,"depthScoreParts":{"impact":2.8,"likelihood":0,"exploitation":0,"ransomware":0},"changes":[]}