{"id":"CVE-2026-68136","url":"https://www.cyber-defence.io/tools/cve/CVE-2026-68136","generatedAt":"2026-10-28T04:01:56.170Z","title":"In the Linux kernel, the following vulnerability has been resolved: net: gro: fix double aggregation of flush-marked skbs Commit 0ab03f353d36 (\"net-gro: Fix GRO flush when receiving a GSO packet.\") added a flush check to skb_gro_receive(), but…","description":"In the Linux kernel, the following vulnerability has been resolved:\n\nnet: gro: fix double aggregation of flush-marked skbs\n\nCommit 0ab03f353d36 (\"net-gro: Fix GRO flush when receiving a GSO\npacket.\") added a flush check to skb_gro_receive(), but\nskb_gro_receive_list() lacks the same validation.\n\nAs a result, packets marked with NAPI_GRO_CB(skb)->flush may still be\nre-aggregated.\n\nThis allows already-GRO'd packets with existing frag_list to be\nre-aggregated into a new GRO session, corrupting the frag_list chain\nstructure. When skb_segment() attempts to unpack these malformed packets,\nit encounters invalid state and triggers a kernel panic.\n\nScenario (Tethering/Device forwarding):\n  1. Driver: Generated aggregated packet P1 via LRO with frag_list\n  2. Dev A: Receives aggregated fraglist packet and flush flag set\n  3. Dev A: Re-enters GRO, skb_gro_receive_list() is called\n  4. Missing flush check allows re-aggregation despite flush flag\n  5. Frag_list chain becomes corrupted (loops or dangling refs)\n  6. Dev B: TX path calls skb_segment(), crashes on corrupted frag_list\n\nRoot cause in skb_segment():\n  The check at line ~4891:\n    if (hsize <= 0 && i >= nfrags && skb_headlen(list_skb) &&\n        (skb_headlen(list_skb) == len || sg)) {\n\n  When frag_list is corrupted by double aggregation, when list_skb is\n  a NULL pointer from skb->next, skb_headlen(list_skb) dereference\n  NULL/corrupted pointers occurs.\n\nCall Trace:\n skb_headlen(NULL skb)\n skb_segment\n tcp_gso_segment\n tcp4_gso_segment\n inet_gso_segment\n skb_mac_gso_segment\n __skb_gso_segment\n skb_gso_segment\n validate_xmit_skb\n validate_xmit_skb_list\n sch_direct_xmit\n qdisc_restart\n __qdisc_run\n qdisc_run\n net_tx_action\n\nFix: Add NAPI_GRO_CB(skb)->flush validation to the early-return check in\nskb_gro_receive_list(), matching the defensive programming pattern of\nskb_gro_receive().","published":"2026-08-10T13:19:59.000Z","lastModified":"2026-10-19T21:17:53.000Z","status":"Received","sourceIdentifier":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","cvss":{"version":"3.1","score":9.8,"severity":"CRITICAL","vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H"},"cwe":["CWE-476"],"affected":[],"epss":{"score":0.00539,"percentile":0.45176,"date":"2026-10-27","history":[]},"kev":{"listed":false},"exploits":{"count":0,"verified":false,"firstPublished":null,"source":"Exploit-DB (https://gitlab.com/exploit-database/exploitdb)","entries":[]},"verdict":{"level":"high","text":"High impact if exploited, but EPSS currently rates exploitation as unlikely (0.54%). Schedule it in the normal patch cycle and watch for a rise in EPSS or a public exploit."},"changes":[],"references":[{"url":"https://git.kernel.org/stable/c/107e1a469f53a2a70874f3f12bf6fcd23925da1d","source":"416baaa9-dc9f-4396-8d5f-8c081fb06d67"},{"url":"https://git.kernel.org/stable/c/7fc7e35212cf58c134310fb47566a844297ceae9","source":"416baaa9-dc9f-4396-8d5f-8c081fb06d67"},{"url":"https://git.kernel.org/stable/c/a4dfd46cc8f08a29c6183794790547d0945f3d45","source":"416baaa9-dc9f-4396-8d5f-8c081fb06d67"},{"url":"https://git.kernel.org/stable/c/d1fb23f8f794ac4683127bd49a6422bd87e0ac02","source":"416baaa9-dc9f-4396-8d5f-8c081fb06d67"},{"url":"https://git.kernel.org/stable/c/db3e82da616f52e2b27e25e7be3fde2f2a5e54d6","source":"416baaa9-dc9f-4396-8d5f-8c081fb06d67"},{"url":"https://git.kernel.org/stable/c/e751256486d0ded20f5a9f9863467f1dce65142f","source":"416baaa9-dc9f-4396-8d5f-8c081fb06d67"},{"url":"https://git.kernel.org/stable/c/fc0c0f7a207f0cd2d2aa725696c907f7d03af9e0","source":"416baaa9-dc9f-4396-8d5f-8c081fb06d67"}],"sources":{"nvd":"https://nvd.nist.gov/vuln/detail/CVE-2026-68136","epss":"https://www.first.org/epss/","kev":"https://www.cisa.gov/known-exploited-vulnerabilities-catalog","exploitdb":"https://www.exploit-db.com/"},"licence":"CC BY 4.0 — link back to the CVE Explorer if you publish the results; upstream data remains subject to its own terms."}