{"id":"CVE-2026-80725","title":"net: gro: properly validate BIG TCP aggregation criteria","summary":"In the Linux kernel, the following vulnerability has been resolved:\n\nnet: gro: properly validate BIG TCP aggregation criteria\n\nWhen GRO attempts to aggregate packets beyond GRO_LEGACY_MAX_SIZE (64KB),\nBIG TCP should only be permitted for…","severity":"critical","cvss":9.8,"cvssVector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H","cvssSource":"cna","vendor":"Linux","product":"Linux","affected":["Linux >= 0fe79f28bfaf73b66b7b1562d2468f94aa03bd12 < 37a5dcd6837fc2afc44a7bc3ed8af4e983783d46","Linux >= 0fe79f28bfaf73b66b7b1562d2468f94aa03bd12 < e907bf694ed55bdfe421be99dba35751a655df25","Linux >= 0fe79f28bfaf73b66b7b1562d2468f94aa03bd12 < 03cb8cc2961f5f781d12e903782cb3815ed84b1c","Linux >= 0fe79f28bfaf73b66b7b1562d2468f94aa03bd12 < 3ce832e2bd431d0c12ba525ed73ad8fbc4191da5","Linux >= 0fe79f28bfaf73b66b7b1562d2468f94aa03bd12 < 81be30c1f5f2bffda1f04c0efd0746af10b9643a","Linux 5.19"],"ssvc":{"exploitation":"none","automatable":"yes","technicalImpact":"total","timestamp":"2026-10-16T19:21:06.422941Z"},"published":"2026-08-29","updated":"2026-10-16","sourceUpdated":"2026-10-16T19:26:35.734Z","source":"CVEORG","sourceUrl":"https://www.cve.org/CVERecord?id=CVE-2026-80725","references":[{"url":"https://git.kernel.org/stable/c/37a5dcd6837fc2afc44a7bc3ed8af4e983783d46"},{"url":"https://git.kernel.org/stable/c/e907bf694ed55bdfe421be99dba35751a655df25"},{"url":"https://git.kernel.org/stable/c/03cb8cc2961f5f781d12e903782cb3815ed84b1c"},{"url":"https://git.kernel.org/stable/c/3ce832e2bd431d0c12ba525ed73ad8fbc4191da5"},{"url":"https://git.kernel.org/stable/c/81be30c1f5f2bffda1f04c0efd0746af10b9643a"}],"tags":["cve.org"],"epss":0.00459,"epssPercentile":0.38329,"ingestedAt":"2026-10-16T19:46:24.302Z","slug":"CVE-2026-80725","body":"## Overview\n\nIn the Linux kernel, the following vulnerability has been resolved:\n\nnet: gro: properly validate BIG TCP aggregation criteria\n\nWhen GRO attempts to aggregate packets beyond GRO_LEGACY_MAX_SIZE (64KB),\nBIG TCP should only be permitted for plain IPv4 TCP and plain IPv6 TCP\n(with sufficient MAC header room to insert the temporary HBH jumbo header).\n\nHowever, commit b1a78b9b9886 (\"net: add support for ipv4 big tcp\")\nloosened the check in skb_gro_receive(), leading to several issues:\n\n1. skb_gro_receive() checked skb_headroom(p) instead of the actual space\n   before the MAC header (p->mac_header). Because skb_headroom(p) includes\n   mac_len, crafted frames (e.g. injected via AF_PACKET) can pass the check\n   with p->mac_header < 8 bytes. When ipv6_gro_complete() inserts the\n   temporary HBH jumbo header, the memmove() starts before skb->head,\n   causing an out-of-bounds write and wrapping skb->mac_header.\n2. It allowed non-IP protocols such as software VLAN (ETH_P_8021Q /\n   ETH_P_8021AD) to aggregate beyond 64KB because\n   p->protocol != ETH_P_IPV6 was true.\n3. It checked p->encapsulation instead of NAPI_GRO_CB(skb)->encap_mark,\n   allowing encapsulated flows (e.g. SIT / IPv6-in-IPv4) to aggregate\n   beyond 64KB.\n\nFix skb_gro_receive() to strictly enforce:\n- NAPI_GRO_CB(skb)->proto == IPPROTO_TCP\n- Not encapsulated (!NAPI_GRO_CB(skb)->encap_mark && !p->encapsulation)\n- Protocol must be either ETH_P_IP or ETH_P_IPV6\n- If ETH_P_IPV6, p->mac_header must be at least\n  sizeof(struct hop_jumbo_hdr)\n\nReturning -E2BIG from skb_gro_receive() ensures that packets which cannot\nbecome BIG TCP are cleanly flushed at <= 64KB and delivered intact without\ndropping.\n\nThis issue does not exist in mainline (7.0+) because the subsystem was\nrewritten in commit 81be30c1f5f2 (\"net/ipv6: Drop HBH for BIG TCP on RX\nside\"), making this fix relevant only for older stable branches like\n6.18.y.\n\n## Affected\n\n- `Linux >= 0fe79f28bfaf73b66b7b1562d2468f94aa03bd12 < 37a5dcd6837fc2afc44a7bc3ed8af4e983783d46`\n- `Linux >= 0fe79f28bfaf73b66b7b1562d2468f94aa03bd12 < e907bf694ed55bdfe421be99dba35751a655df25`\n- `Linux >= 0fe79f28bfaf73b66b7b1562d2468f94aa03bd12 < 03cb8cc2961f5f781d12e903782cb3815ed84b1c`\n- `Linux >= 0fe79f28bfaf73b66b7b1562d2468f94aa03bd12 < 3ce832e2bd431d0c12ba525ed73ad8fbc4191da5`\n- `Linux >= 0fe79f28bfaf73b66b7b1562d2468f94aa03bd12 < 81be30c1f5f2bffda1f04c0efd0746af10b9643a`\n- `Linux 5.19`\n\n## Remediation\n\nRefer to the linked advisories for vendor-supplied fixes and affected version ranges.","depth":"midnight","depthScore":54,"depthScoreParts":{"impact":53.9,"likelihood":0.1,"exploitation":0,"ransomware":0},"changes":[]}