{"id":"CVE-2026-98377","published":"2026-10-09T08:16:56.010","lastModified":"2026-10-09T08:16:56.010","description":"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 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.","cvssScore":null,"cvssSeverity":null,"cvssVector":null,"cwes":[],"vendors":[],"products":[],"references":[{"url":"https://git.kernel.org/stable/c/40a5cc4b7251c74f3341332a226d02200e96bccf","tags":[]},{"url":"https://git.kernel.org/stable/c/59af43ccece4d2d8b62e9e3ccc96b6e2e793bcdc","tags":[]},{"url":"https://git.kernel.org/stable/c/ab888242fce4f16f6c4d4c6ec53939ad36aa3b3a","tags":[]},{"url":"https://git.kernel.org/stable/c/f42562dd027dc4ed103fae17b2206e73ea1963c4","tags":[]}],"exploitRefs":[],"hasPoc":false,"ai":null}