{"id":"CVE-2026-98377","title":"In the Linux kernel, the following vulnerability has been resolved:\n\nvlan: require the MAC header to be present in __vlan_insert_inner_tag()\n\n__vlan_insert_inner_tag() only guarantees head room via skb_cow_head(),\nnever that mac_len byte…","summary":"In the Linux kernel, the following vulnerability has been resolved:\n\nvlan: require the MAC header to be present in __vlan_insert_inner_tag()\n\n__vlan_insert_inner_tag() only guarantees head room via skb_cow_head(),\nnever that mac_len byte…","severity":"high","published":"2026-10-09","updated":"2026-10-09","sourceUpdated":"2026-10-09T08:16:56.010","source":"NVD","sourceUrl":"https://nvd.nist.gov/vuln/detail/CVE-2026-98377","references":[{"url":"https://git.kernel.org/stable/c/40a5cc4b7251c74f3341332a226d02200e96bccf","label":"416baaa9-dc9f-4396-8d5f-8c081fb06d67"},{"url":"https://git.kernel.org/stable/c/59af43ccece4d2d8b62e9e3ccc96b6e2e793bcdc","label":"416baaa9-dc9f-4396-8d5f-8c081fb06d67"},{"url":"https://git.kernel.org/stable/c/ab888242fce4f16f6c4d4c6ec53939ad36aa3b3a","label":"416baaa9-dc9f-4396-8d5f-8c081fb06d67"},{"url":"https://git.kernel.org/stable/c/f42562dd027dc4ed103fae17b2206e73ea1963c4","label":"416baaa9-dc9f-4396-8d5f-8c081fb06d67"},{"url":"https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-98377.json"},{"url":"https://access.redhat.com/security/cve/CVE-2026-98377"},{"url":"https://bugzilla.redhat.com/show_bug.cgi?id=2548389"},{"url":"https://www.cve.org/CVERecord?id=CVE-2026-98377"},{"url":"https://nvd.nist.gov/vuln/detail/CVE-2026-98377"},{"url":"https://git.kernel.org/pub/scm/linux/security/vulns.git/plain/cve/published/2026/CVE-2026-98377.mbox"},{"url":"https://git.kernel.org/stable/c/3d531429524df2c7116579306640283fea68bcf0"}],"tags":["nvd","csaf","vex","red-hat","cve.org"],"ingestedAt":"2026-10-09T08:29:41.350Z","vendor":"Red Hat","product":"Red Hat Enterprise Linux 9","affected":["enterprise_linux 10","enterprise_linux 6","enterprise_linux 7","enterprise_linux 8","enterprise_linux 9","openshift_container_platform 4"],"cvss":7,"cvssVector":"CVSS:3.1/AV:L/AC:H/PR:L/UI:N/S:U/C:H/I:H/A:H","cvssSource":"vendor","cwe":["CWE-125"],"epss":0.00162,"epssPercentile":0.05374,"slug":"CVE-2026-98377","body":"## Overview\n\nIn the Linux kernel, the following vulnerability has been resolved:\n\nvlan: require the MAC header to be present in __vlan_insert_inner_tag()\n\n__vlan_insert_inner_tag() only guarantees head room via skb_cow_head(),\nnever that mac_len bytes of MAC header are present.  Its ETH_HLEN\nwrappers - __vlan_insert_tag() under skb_vlan_push(), and\nvlan_insert_tag() under validate_xmit_vlan() on the generic transmit\npath - therefore rewrite the first 16 bytes at skb->data: a 12-byte\nmemmove plus two 2-byte stores at +12 and +14.  No caller supplies the\nbound, while the pop helpers use skb_ensure_writable()/pskb_may_pull().\n\nAn IFF_TUN device has hard_header_len == 0, so packet_snd() accepts a\none-byte AF_PACKET/SOCK_RAW frame.  The first vlan push only sets a\nhwaccel tag; the next - clsact \"action vlan push\" or\nbpf_skb_vlan_push() - enters the helper with skb->len still 1.  The\nhead comes from skbuff_small_head without __GFP_ZERO, so each push\ndrags bytes from beyond skb->tail into the frame.  After three the\none-byte send leaves as 13 bytes carrying 11 bytes of uninitialised\nslab:\n\n  0000: 5a b3 62 12 80 88 ff ff 00 b3 62 12 81\n           `------------------------------'\n  only 0x5a was sent; the rest is slab, here the top 56 bits of a\n  linear-map address\n\nRequire the MAC header the helper rewrites to be present, so such a\nframe is dropped rather than transmitted.\n\n## Remediation\n\nRefer to the linked advisories for vendor-supplied fixes and affected version ranges.\n\n## Vendor advisories\n\n- **Red Hat VEX** · Moderate · affected: Red Hat Enterprise Linux 10, Red Hat Enterprise Linux 6, Red Hat Enterprise Linux 7, Red Hat Enterprise Linux 8, Red Hat Enterprise Linux 9, Red Hat OpenShift Container Platform 4 · no fix planned: Red Hat Enterprise Linux 6, Red Hat Enterprise Linux 10, Red Hat Enterprise Linux 7, Red Hat Enterprise Linux 8, … · updated 2026-10-10 · [vex](https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-98377.json)","depth":"twilight","depthScore":39,"depthScoreParts":{"impact":38.5,"likelihood":0,"exploitation":0,"ransomware":0},"changes":[{"seq":219115,"id":"CVE-2026-98377","ts":1791707065741,"field":"cvss","old":null,"new":"7"},{"seq":219114,"id":"CVE-2026-98377","ts":1791707065741,"field":"severity","old":"none","new":"high"}]}