{"cve":"CVE-2026-89722","nvd":{"published":"2026-09-11T20:20:01.370","modified":"2026-10-19T09:18:12.380","status":"Received","description":"In the Linux kernel, the following vulnerability has been resolved:\n\nPCI/sysfs: Fix out-of-bounds read in pci_write_legacy_io()\n\npci_write_legacy_io() loads 4 bytes from the kernfs write buffer\nregardless of how many bytes userspace wrote:\n\n  if (count != 1 && count != 2 && count != 4)\n          return -EINVAL;\n\n  return pci_legacy_write(bus, off, *(u32 *)buf, count);\n\nkernfs_fop_write_iter() allocates the buffer with kmalloc(len + 1),\nso a 1-byte write to the legacy_io sysfs file allocates 2 bytes and\nthe unconditional u32 load reads up to 2 bytes past the end of the\nallocation, which KASAN reports as a slab-out-of-bounds read.\nSimilarly, a 2-byte write overreads by 1 byte.\n\nThus, read only the number of bytes requested using get_unaligned_le16()\nand get_unaligned_le32() for the 2 and 4 byte cases, interpreting the\nbuffer as little-endian to match the byte ordering of PCI I/O port\nspace.\n\nThe PowerPC implementation previously compensated for the generic\ncode's native-endian 32-bit load by shifting the value into place\nfor the 1 and 2 byte cases.  The shifts were only correct on\nbig-endian kernels.\n\nOn little-endian PowerPC (POWER8 and later), they extracted the wrong\nbytes, so a 1-byte write wrote an out-of-bounds byte instead of the\nrequested value.  On big-endian, the native load also caused out_le16()\nand out_le32() to reverse the user's bytes on the wire for 2 and 4 byte\nwrites.  The little-endian helpers resolve both issues, so the shifts\nare removed.\n\nNo changes are needed for the Alpha platform.\n\nThe legacy_io file is root-only and exists only on Alpha and PowerPC,\nthe two architectures that define HAVE_PCI_LEGACY.","cvss_v4":null,"cvss_v3":null,"cwes":[],"references":["https://git.kernel.org/stable/c/7a99e9c7011905734cc2739038f2a224b6be0d1f","https://git.kernel.org/stable/c/dc76258d0132df1d831a5a29758bd448ca9c566e","https://git.kernel.org/stable/c/e892f05f1f790d5721cd8e3c561ed76da7e08bae"],"products":[],"source":"nvd","synced_at":"2026-10-19T22:53:43.293028046+00:00"},"epss":{"cve":"CVE-2026-89722","score":0.00206,"percentile":0.10609,"date":"2026-10-26"},"kev":null,"osv":[],"attribution":["This product uses the NVD API but is not endorsed or certified by the NVD.","EPSS scores: FIRST Exploit Prediction Scoring System, https://www.first.org/epss","Known exploited vulnerabilities: CISA Known Exploited Vulnerabilities Catalog, https://www.cisa.gov/known-exploited-vulnerabilities-catalog","Package advisories: OSV (https://osv.dev), from the GitHub Advisory Database, PyPA, Go, RustSec and other ecosystem databases, under CC-BY 4.0 or CC0","CVE records: the CVE Program's CVE List (https://www.cve.org), under its terms of use (https://www.cve.org/Legal/TermsOfUse). CVE is a registered trademark of The MITRE Corporation; this product is not affiliated with the CVE Program."]}