{"cve":"CVE-2026-52940","nvd":{"published":"2026-06-24T08:16:24.287","modified":"2026-07-08T19:12:57.360","status":"Analyzed","description":"In the Linux kernel, the following vulnerability has been resolved:\n\ntun: zero the whole vnet header in tun_put_user()\n\ntun_put_user() declares an on-stack struct virtio_net_hdr_v1_hash_tunnel\nwithout zeroing it. For a non-tunnel skb, virtio_net_hdr_tnl_from_skb()\nonly initializes the first 10 bytes (sizeof(struct virtio_net_hdr)),\nleaving bytes 10..23 (num_buffers and the hash/tunnel fields) as stack\ngarbage.\n\nAn unprivileged user can set the vnet header size to 24 with\nTUNSETVNETHDRSZ, so __tun_vnet_hdr_put() copies all 24 bytes of the\npartially-initialized struct to userspace, leaking 14 bytes of kernel\nstack on every read of a non-tunnel packet.\n\nFix it the same way tun_get_user() already does by zeroing the whole\nheader right after declaration.","cvss_v4":null,"cvss_v3":{"version":"3.1","vector":"CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H","score":5.5},"cwes":[],"references":["https://git.kernel.org/stable/c/585cb85e9a29185be05f326369573c2663cf4380","https://git.kernel.org/stable/c/5fd1fa5a4254bfdd70571c77f5e3bcb4e43738d5","https://git.kernel.org/stable/c/7f2fcff15e99bb852f6967396ed12b38376e2c8d"],"products":["linux:linux_kernel"],"source":"nvd","synced_at":"2026-10-19T22:41:17.107060303+00:00"},"epss":{"cve":"CVE-2026-52940","score":0.0016,"percentile":0.05158,"date":"2026-10-31"},"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."]}