{"api_version":"1","generated_at":"2026-09-12T20:46:28+00:00","cve":"CVE-2026-31521","urls":{"html":"https://cve.report/CVE-2026-31521","api":"https://cve.report/api/cve/CVE-2026-31521.json","docs":"https://cve.report/api","cve_org":"https://www.cve.org/CVERecord?id=CVE-2026-31521","nvd":"https://nvd.nist.gov/vuln/detail/CVE-2026-31521"},"summary":{"title":"module: Fix kernel panic when a symbol st_shndx is out of bounds","description":"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 (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/","state":"PUBLISHED","assigner":"Linux","published_at":"2026-04-22 14:16:51","updated_at":"2026-07-14 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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] 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13:18:44","problem_types":["CWE-787"],"metrics":{"cvssMetricV31":[{"source":"nvd@nist.gov","type":"Primary","cvssData":{"version":"3.1","vectorString":"CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H","baseScore":5.5,"baseSeverity":"MEDIUM","attackVector":"LOCAL","attackComplexity":"LOW","privilegesRequired":"LOW","userInteraction":"NONE","scope":"UNCHANGED","confidentialityImpact":"NONE","integrityImpact":"NONE","availabilityImpact":"HIGH"},"exploitabilityScore":1.8,"impactScore":3.6}]},"configurations":[{"nodes":[{"operator":"OR","negate":false,"cpeMatch":[{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"2.6.12.1","versionEndExcluding":"5.15.203","matchCriteriaId":"A0A14F27-2B54-495E-9E83-FD1A2D3AC85C"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"5.16","versionEndExcluding":"6.1.168","matchCriteriaId":"E2DDDCA1-6DAB-4018-B920-8F045DDD8D3B"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"6.2","versionEndExcluding":"6.6.131","matchCriteriaId":"CE6ED4D4-0046-4573-BFA9-D64143B6A89F"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"6.7","versionEndExcluding":"6.12.80","matchCriteriaId":"97EB19EC-A11E-49C6-9D2F-6F6EC6CB98B6"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"6.13","versionEndExcluding":"6.18.21","matchCriteriaId":"ED39847A-3B46-4729-B7CA-B2C30B9FA8FE"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"6.19","versionEndExcluding":"6.19.11","matchCriteriaId":"4CA2E747-A9EC-4518-9AA2-B4247FC748B7"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:2.6.12:-:*:*:*:*:*:*","matchCriteriaId":"6F62EECE-8FB1-4D57-85D8-CB9E23CF313C"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:2.6.12:rc2:*:*:*:*:*:*","matchCriteriaId":"4F76C298-81DC-43E4-8FC9-DC005A2116EF"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:2.6.12:rc3:*:*:*:*:*:*","matchCriteriaId":"0AB349B2-3F78-4197-882B-90ADB3BF645A"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:2.6.12:rc4:*:*:*:*:*:*","matchCriteriaId":"6AC88830-A9BC-4607-B572-A4B502FC9FD0"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:2.6.12:rc5:*:*:*:*:*:*","matchCriteriaId":"476CB3A5-D022-4F13-AAEF-CB6A5785516A"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:7.0:rc1:*:*:*:*:*:*","matchCriteriaId":"F253B622-8837-4245-BCE5-A7BF8FC76A16"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:7.0:rc2:*:*:*:*:*:*","matchCriteriaId":"4AE85AD8-4641-4E7C-A2F4-305E2CD9EE64"}]}]}]},"legacy_mitre":{"record":{"CveYear":"2026","CveId":"31521","Ordinal":"1","Title":"module: Fix kernel panic when a symbol st_shndx is out of bounds","CVE":"CVE-2026-31521","Year":"2026"},"notes":[{"CveYear":"2026","CveId":"31521","Ordinal":"1","NoteData":"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 (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/","Type":"Description","Title":"module: Fix kernel panic when a symbol st_shndx is out of bounds"}]}}}