{"id":"CVE-2026-99055","title":"tcp: reject net_iov in zerocopy receive mapping hints","summary":"In the Linux kernel, the following vulnerability has been resolved:\n\ntcp: reject net_iov in zerocopy receive mapping hints\n\nAfter copying a readable prefix, receive_fallback_to_copy() asks\ntcp_zerocopy_set_hint_for_skb() where page mappi…","severity":"none","vendor":"Linux","product":"Linux","affected":["Linux >= 9f6b619edf2e85746f261b42ae8f818a59d126f7 < 563d3564513496b9ce3b3ba7a5154427554d0f06","Linux >= 9f6b619edf2e85746f261b42ae8f818a59d126f7 < 1c7463ac0e99cc91c4eecc1b69a740ef1a619932","Linux >= 9f6b619edf2e85746f261b42ae8f818a59d126f7 < 3aa6f536a95eb0617c313ae2eb76fdfa85331f85","Linux >= 9f6b619edf2e85746f261b42ae8f818a59d126f7 < 8b1f0af1fd5fd113432233ed8a3862ee7c30a84f","Linux 6.12"],"published":"2026-10-23","updated":"2026-10-23","sourceUpdated":"2026-10-23T12:22:39.451Z","source":"CVEORG","sourceUrl":"https://www.cve.org/CVERecord?id=CVE-2026-99055","references":[{"url":"https://git.kernel.org/stable/c/563d3564513496b9ce3b3ba7a5154427554d0f06"},{"url":"https://git.kernel.org/stable/c/1c7463ac0e99cc91c4eecc1b69a740ef1a619932"},{"url":"https://git.kernel.org/stable/c/3aa6f536a95eb0617c313ae2eb76fdfa85331f85"},{"url":"https://git.kernel.org/stable/c/8b1f0af1fd5fd113432233ed8a3862ee7c30a84f"}],"tags":["cve.org"],"ingestedAt":"2026-10-23T13:24:55.523Z","slug":"CVE-2026-99055","body":"## Overview\n\nIn the Linux kernel, the following vulnerability has been resolved:\n\ntcp: reject net_iov in zerocopy receive mapping hints\n\nAfter copying a readable prefix, receive_fallback_to_copy() asks\ntcp_zerocopy_set_hint_for_skb() where page mapping can resume. If the\nnext skb is unreadable, find_next_mappable_frag() passes its net_iov\nfragment to can_map_frag().\n\nskb_frag_page() returns NULL for a net_iov, but can_map_frag()\ndereferences it in PageCompound(). A v7.2 KASAN run on a connected TCP\nsocket with 64 readable bytes followed by a 4096-byte NET_IOV_DMABUF\nfragment reported:\n\n  BUG: KASAN: null-ptr-deref in can_map_frag\n  tcp_zerocopy_receive -> can_map_frag\n  Kernel panic - not syncing: KASAN: panic_on_warn set\n\nThe diagnostic inserted the net_iov directly because the test host has\nno devmem-capable NIC. Hardware end-to-end reachability remains untested\nand requires CONFIG_NET_DEVMEM plus a supported DMA-buf-bound RX queue.\n\nReject all net_iov fragments before skb_frag_page(). This covers both\nDMABUF and IOURING net_iov types while leaving page-backed checks\nunchanged. With the guard, the same queue copied the readable prefix,\nreturned a 4096-byte skip hint, and completed without a fault.\n\n## Affected\n\n- `Linux >= 9f6b619edf2e85746f261b42ae8f818a59d126f7 < 563d3564513496b9ce3b3ba7a5154427554d0f06`\n- `Linux >= 9f6b619edf2e85746f261b42ae8f818a59d126f7 < 1c7463ac0e99cc91c4eecc1b69a740ef1a619932`\n- `Linux >= 9f6b619edf2e85746f261b42ae8f818a59d126f7 < 3aa6f536a95eb0617c313ae2eb76fdfa85331f85`\n- `Linux >= 9f6b619edf2e85746f261b42ae8f818a59d126f7 < 8b1f0af1fd5fd113432233ed8a3862ee7c30a84f`\n- `Linux 6.12`\n\n## Remediation\n\nRefer to the linked advisories for vendor-supplied fixes and affected version ranges.","depth":"sunlit","depthScore":3,"depthScoreParts":{"impact":2.8,"likelihood":0,"exploitation":0,"ransomware":0},"changes":[]}