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].stshndx].shaddr; sym[i].st_value += secbase; break; } }
A symbol with an out-of-bounds stshndx value, for example 0xffff (known as SHNXINDEX 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 simplifysymbols() to validate that stshndx 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/
{
"cna_assigner": "Linux",
"osv_generated_from": "https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/31xxx/CVE-2026-31521.json"
}