CVE-2026-89722
Low risk· EPSS 10%Exploitation Probability (EPSS)
Low risk10th percentile - higher than 10% of all known CVEs
Summary
A vulnerability was fixed in the Linux kernel's pci_write_legacy_io() function in the PCI/sysfs subsystem. The function unconditionally loaded 4 bytes from the kernfs write buffer even when userspace wrote only 1 or 2 bytes, causing an out-of-bounds read of the allocated memory (slab-out-of-bounds). Additionally, on little-endian PowerPC (POWER8 and later), byte shifts caused an out-of-bounds byte write instead of the requested value.
Risk Assessment
The vulnerability affects the legacy_io file, which is root-only and exists only on Alpha and PowerPC architectures. It can lead to out-of-bounds kernel memory reads (reported by KASAN) and incorrect writes to PCI I/O space, potentially causing system instability.
Recommendation
Update the Linux kernel to a version containing the fix that uses get_unaligned_le16() and get_unaligned_le32() to read exactly the requested number of bytes. If updating is not possible, restrict access to the legacy_io file to trusted root users only on Alpha and PowerPC systems.
Other vulnerabilities in Linux kernel
See all- CVE-2026-98162Unknown
In the Linux kernel, the smb2_tree_connect() function of the SMB server (ksmbd) leaks a tree connection. When ksmbd_iov_pin_rsp() fails, the newly created tree connection is not disconnected, leading to a resource leak.
- CVE-2026-98160Unknown
In the Linux kernel, the staging rtl8723bs driver's rtw_sdio_if1_init() function frees padapter->HalData with kfree(), even though it was allocated via vzalloc(). Using kfree() to release a vmalloc-backed buffer can lead to memory corruption.
- CVE-2026-100079Unknown
In the Linux kernel, the USB Type-C (ucsi) subsystem's ucsi_register() creates per-instance debugfs entries, but ucsi_unregister() keeps them until ucsi_destroy(). Drivers like ucsi_glink that unregister/register the same UCSI instance across remoteproc restart then try to create an already existing debugfs directory.
- CVE-2026-100078Unknown
In the Linux kernel, the iwlwifi (mei) driver's iwl_mei_write_cyclic_buf() function receives an incorrect first argument — the q_head pointer is passed instead of cldev. The bug has been fixed.
- CVE-2026-100077Unknown
In the Linux kernel, the drm/msm driver does not safely retire a hung submit before GPU recovery completes. Retiring the submit triggers BO free, which can result in GPU pagefaults since the GPU may be actively accessing those BOs.
- CVE-2026-100074Unknown
In the Linux kernel, a bug was fixed where the BPF_REFCOUNT field was not marked as unique, although it should be. The fix addresses this oversight.
- CVE-2026-100073Unknown
In the Linux kernel, a bug in the ext4 filesystem related to transaction overflow during writeback was fixed. A previous fix was too eager in reducing reserved transaction credits, leading to insufficient reservation in some corner cases. The fix uses ext4_meta_trans_blocks() for a correct upper bound estimate.
- CVE-2026-100072Unknown
In the Linux kernel, a problem in the ACPI subsystem was fixed where the use of acpi_get_first_physical_node() in acpi_platform_fill_resource() and acpi_create_platform_device() was unsafe because the returned device could be freed at any time. The fix replaces it with acpi_bus_get_primary_device() and adjusts the code to call it only once.
- CVE-2026-100071Unknown
In the Linux kernel, a memory leak in the HSR (High-availability Seamless Redundancy) module was fixed. When hsr_dev_finalize() fails after registering an RX handler, dynamic nodes learned in that window are not released. The fix frees both dynamic databases in the error unwind path.
- CVE-2026-100070Unknown
In the Linux kernel, a bug in the netfilter nf_nat_sip module was fixed where the offset was not rewound when NAT shrinks the packet. If map_addr() changes the packet length, coff may point to an incorrect position, potentially causing subsequent Contact headers to be skipped and leaking internal network details.
Original NVD description (English source)
In the Linux kernel, the following vulnerability has been resolved: PCI/sysfs: Fix out-of-bounds read in pci_write_legacy_io() pci_write_legacy_io() loads 4 bytes from the kernfs write buffer regardless of how many bytes userspace wrote: if (count != 1 && count != 2 && count != 4) return -EINVAL; return pci_legacy_write(bus, off, *(u32 *)buf, count); kernfs_fop_write_iter() allocates the buffer with kmalloc(len + 1), so a 1-byte write to the legacy_io sysfs file allocates 2 bytes and the unconditional u32 load reads up to 2 bytes past the end of the allocation, which KASAN reports as a slab-out-of-bounds read. Similarly, a 2-byte write overreads by 1 byte. Thus, read only the number of bytes requested using get_unaligned_le16() and get_unaligned_le32() for the 2 and 4 byte cases, interpreting the buffer as little-endian to match the byte ordering of PCI I/O port space. The PowerPC implementation previously compensated for the generic code's native-endian 32-bit load by shifting the value into place for the 1 and 2 byte cases. The shifts were only correct on big-endian kernels. On little-endian PowerPC (POWER8 and later), they extracted the wrong bytes, so a 1-byte write wrote an out-of-bounds byte instead of the requested value. On big-endian, the native load also caused out_le16() and out_le32() to reverse the user's bytes on the wire for 2 and 4 byte writes. The little-endian helpers resolve both issues, so the shifts are removed. No changes are needed for the Alpha platform. The legacy_io file is root-only and exists only on Alpha and PowerPC, the two architectures that define HAVE_PCI_LEGACY.
Vulnerability data from NVD (NIST) · CISA KEV · EPSS