{"api_version":"1","generated_at":"2026-06-24T12:16:59+00:00","cve":"CVE-2026-52940","urls":{"html":"https://cve.report/CVE-2026-52940","api":"https://cve.report/api/cve/CVE-2026-52940.json","docs":"https://cve.report/api","cve_org":"https://www.cve.org/CVERecord?id=CVE-2026-52940","nvd":"https://nvd.nist.gov/vuln/detail/CVE-2026-52940"},"summary":{"title":"tun: zero the whole vnet header in tun_put_user()","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.","state":"PUBLISHED","assigner":"Linux","published_at":"2026-06-24 08:16:24","updated_at":"2026-06-24 08:16:24"},"problem_types":[],"metrics":[],"references":[{"url":"https://git.kernel.org/stable/c/7f2fcff15e99bb852f6967396ed12b38376e2c8d","name":"https://git.kernel.org/stable/c/7f2fcff15e99bb852f6967396ed12b38376e2c8d","refsource":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","tags":[],"title":"","mime":"","httpstatus":"","archivestatus":"0"},{"url":"https://git.kernel.org/stable/c/585cb85e9a29185be05f326369573c2663cf4380","name":"https://git.kernel.org/stable/c/585cb85e9a29185be05f326369573c2663cf4380","refsource":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","tags":[],"title":"","mime":"","httpstatus":"","archivestatus":"0"},{"url":"https://git.kernel.org/stable/c/5fd1fa5a4254bfdd70571c77f5e3bcb4e43738d5","name":"https://git.kernel.org/stable/c/5fd1fa5a4254bfdd70571c77f5e3bcb4e43738d5","refsource":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","tags":[],"title":"","mime":"","httpstatus":"","archivestatus":"0"},{"url":"https://www.cve.org/CVERecord?id=CVE-2026-52940","name":"CVE Program record","refsource":"CVE.ORG","tags":["canonical"]},{"url":"https://nvd.nist.gov/vuln/detail/CVE-2026-52940","name":"NVD vulnerability detail","refsource":"NVD","tags":["canonical","analysis"]}],"affected":[{"source":"CNA","vendor":"Linux","product":"Linux","version":"affected 288f30435132d2f9e7a29ec9b9745a4f9dc7fd37 5fd1fa5a4254bfdd70571c77f5e3bcb4e43738d5 git","platforms":[]},{"source":"CNA","vendor":"Linux","product":"Linux","version":"affected 288f30435132d2f9e7a29ec9b9745a4f9dc7fd37 585cb85e9a29185be05f326369573c2663cf4380 git","platforms":[]},{"source":"CNA","vendor":"Linux","product":"Linux","version":"affected 288f30435132d2f9e7a29ec9b9745a4f9dc7fd37 7f2fcff15e99bb852f6967396ed12b38376e2c8d git","platforms":[]},{"source":"CNA","vendor":"Linux","product":"Linux","version":"affected 6.17","platforms":[]},{"source":"CNA","vendor":"Linux","product":"Linux","version":"unaffected 6.17 semver","platforms":[]},{"source":"CNA","vendor":"Linux","product":"Linux","version":"unaffected 6.18.36 6.18.* semver","platforms":[]},{"source":"CNA","vendor":"Linux","product":"Linux","version":"unaffected 7.0.13 7.0.* semver","platforms":[]},{"source":"CNA","vendor":"Linux","product":"Linux","version":"unaffected 7.1 * original_commit_for_fix","platforms":[]}],"timeline":[],"solutions":[],"workarounds":[],"exploits":[],"credits":[],"nvd_cpes":[],"vendor_comments":[],"enrichments":{"kev":null,"epss":null,"legacy_qids":[]},"source_records":{"cve_program":{"containers":{"cna":{"affected":[{"defaultStatus":"unaffected","product":"Linux","programFiles":["drivers/net/tun.c"],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","vendor":"Linux","versions":[{"lessThan":"5fd1fa5a4254bfdd70571c77f5e3bcb4e43738d5","status":"affected","version":"288f30435132d2f9e7a29ec9b9745a4f9dc7fd37","versionType":"git"},{"lessThan":"585cb85e9a29185be05f326369573c2663cf4380","status":"affected","version":"288f30435132d2f9e7a29ec9b9745a4f9dc7fd37","versionType":"git"},{"lessThan":"7f2fcff15e99bb852f6967396ed12b38376e2c8d","status":"affected","version":"288f30435132d2f9e7a29ec9b9745a4f9dc7fd37","versionType":"git"}]},{"defaultStatus":"affected","product":"Linux","programFiles":["drivers/net/tun.c"],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","vendor":"Linux","versions":[{"status":"affected","version":"6.17"},{"lessThan":"6.17","status":"unaffected","version":"0","versionType":"semver"},{"lessThanOrEqual":"6.18.*","status":"unaffected","version":"6.18.36","versionType":"semver"},{"lessThanOrEqual":"7.0.*","status":"unaffected","version":"7.0.13","versionType":"semver"},{"lessThanOrEqual":"*","status":"unaffected","version":"7.1","versionType":"original_commit_for_fix"}]}],"cpeApplicability":[{"nodes":[{"cpeMatch":[{"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionEndExcluding":"6.18.36","versionStartIncluding":"6.17","vulnerable":true},{"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionEndExcluding":"7.0.13","versionStartIncluding":"6.17","vulnerable":true},{"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionEndExcluding":"7.1","versionStartIncluding":"6.17","vulnerable":true}],"negate":false,"operator":"OR"}]}],"descriptions":[{"lang":"en","value":"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."}],"providerMetadata":{"dateUpdated":"2026-06-24T07:14:29.281Z","orgId":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","shortName":"Linux"},"references":[{"url":"https://git.kernel.org/stable/c/5fd1fa5a4254bfdd70571c77f5e3bcb4e43738d5"},{"url":"https://git.kernel.org/stable/c/585cb85e9a29185be05f326369573c2663cf4380"},{"url":"https://git.kernel.org/stable/c/7f2fcff15e99bb852f6967396ed12b38376e2c8d"}],"title":"tun: zero the whole vnet header in tun_put_user()","x_generator":{"engine":"bippy-1.2.0"}}},"cveMetadata":{"assignerOrgId":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","assignerShortName":"Linux","cveId":"CVE-2026-52940","datePublished":"2026-06-24T07:14:29.281Z","dateReserved":"2026-06-09T07:44:35.370Z","dateUpdated":"2026-06-24T07:14:29.281Z","state":"PUBLISHED"},"dataType":"CVE_RECORD","dataVersion":"5.2"},"nvd":{"publishedDate":"2026-06-24 08:16:24","lastModifiedDate":"2026-06-24 08:16:24","problem_types":[],"metrics":[],"configurations":[]},"legacy_mitre":{"record":{"CveYear":"2026","CveId":"52940","Ordinal":"1","Title":"tun: zero the whole vnet header in tun_put_user()","CVE":"CVE-2026-52940","Year":"2026"},"notes":[{"CveYear":"2026","CveId":"52940","Ordinal":"1","NoteData":"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.","Type":"Description","Title":"tun: zero the whole vnet header in tun_put_user()"}]}}}