CVE-2026-81000
HighCVSS 7.8Exploitation Probability (EPSS)
Low risk6th percentile - higher than 6% of all known CVEs
Summary
In the Linux kernel, tun_get_user() in the TUN/TAP driver uses tun->align both as skb headroom and to decide how much packet data to keep linear. When align exceeds the usable space in a one-page skb head, SKB_MAX_HEAD(align) underflows, the result becomes negative, and after assignment to a size_t it causes skb->data to be placed outside the allocated head. OVS can propagate an oversized headroom request from another port to TUN or TAP.
Risk Assessment
This can lead to kernel memory corruption and potentially privilege escalation or system crash. In environments using OVS with TUN/TAP interfaces the risk is real because oversized headroom can be propagated from an untrusted port.
Recommendation
Update the Linux kernel to a version containing the fix that bounds TUN headroom to the one-page skb budget and the largest non-sentinel 16-bit header offset. If updating is not possible, restrict the ability to propagate large align values through OVS to TUN/TAP interfaces.
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: net: tun: bound receive headroom tun_get_user() uses tun->align both as skb headroom and when choosing how much packet data to keep linear. OVS can propagate an oversized headroom request from another port to TUN or TAP. When align is larger than the usable space in a one-page skb head, SKB_MAX_HEAD(align) underflows and the result becomes negative when stored in good_linear. That value later wraps when assigned to the size_t linear variable, and tun_alloc_skb() can place skb->data outside the allocated head. Bound the headroom stored by TUN to the one-page skb-head budget and the largest non-sentinel 16-bit skb header offset. Leave one linear byte for raw TUN and a complete Ethernet header for TAP, including NET_IP_ALIGN. Also pull the raw-TUN protocol byte and the TAP Ethernet header before accessing them, so these checks remain safe for nonlinear skbs supplied by other allocation paths.
Vulnerability data from NVD (NIST) · CISA KEV · EPSS