CVE-2026-31521

In the Linux kernel, the following vulnerability has been resolved:<br /> <br /> module: Fix kernel panic when a symbol st_shndx is out of bounds<br /> <br /> The module loader doesn&amp;#39;t check for bounds of the ELF section index in<br /> simplify_symbols():<br /> <br /> for (i = 1; i sh_size / sizeof(Elf_Sym); i++) {<br /> const char *name = info-&gt;strtab + sym[i].st_name;<br /> <br /> switch (sym[i].st_shndx) {<br /> case SHN_COMMON:<br /> <br /> [...]<br /> <br /> default:<br /> /* Divert to percpu allocation if a percpu var. */<br /> if (sym[i].st_shndx == info-&gt;index.pcpu)<br /> secbase = (unsigned long)mod_percpu(mod);<br /> else<br /> /** HERE --&gt; **/ secbase = info-&gt;sechdrs[sym[i].st_shndx].sh_addr;<br /> sym[i].st_value += secbase;<br /> break;<br /> }<br /> }<br /> <br /> A symbol with an out-of-bounds st_shndx value, for example 0xffff<br /> (known as SHN_XINDEX or SHN_HIRESERVE), may cause a kernel panic:<br /> <br /> BUG: unable to handle page fault for address: ...<br /> RIP: 0010:simplify_symbols+0x2b2/0x480<br /> ...<br /> Kernel panic - not syncing: Fatal exception<br /> <br /> This can happen when module ELF is legitimately using SHN_XINDEX or<br /> when it is corrupted.<br /> <br /> Add a bounds check in simplify_symbols() to validate that st_shndx is<br /> within the valid range before using it.<br /> <br /> This issue was discovered due to a bug in llvm-objcopy, see relevant<br /> discussion for details [1].<br /> <br /> [1] https://lore.kernel.org/linux-modules/20251224005752.201911-1-ihor.solodrai@linux.dev/