CVE-2026-68136 (GCVE-0-2026-68136)
Vulnerability from cvelistv5
Published
2026-08-10 11:58
Modified
2026-10-19 20:58
Severity ?
9.8 (Critical) - CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
Summary
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 skb_gro_receive_list() lacks the same validation. As a result, packets marked with NAPI_GRO_CB(skb)->flush may still be re-aggregated. This allows already-GRO'd packets with existing frag_list to be re-aggregated into a new GRO session, corrupting the frag_list chain structure. When skb_segment() attempts to unpack these malformed packets, it encounters invalid state and triggers a kernel panic. Scenario (Tethering/Device forwarding): 1. Driver: Generated aggregated packet P1 via LRO with frag_list 2. Dev A: Receives aggregated fraglist packet and flush flag set 3. Dev A: Re-enters GRO, skb_gro_receive_list() is called 4. Missing flush check allows re-aggregation despite flush flag 5. Frag_list chain becomes corrupted (loops or dangling refs) 6. Dev B: TX path calls skb_segment(), crashes on corrupted frag_list Root cause in skb_segment(): The check at line ~4891: if (hsize <= 0 && i >= nfrags && skb_headlen(list_skb) && (skb_headlen(list_skb) == len || sg)) { When frag_list is corrupted by double aggregation, when list_skb is a NULL pointer from skb->next, skb_headlen(list_skb) dereference NULL/corrupted pointers occurs. Call Trace: skb_headlen(NULL skb) skb_segment tcp_gso_segment tcp4_gso_segment inet_gso_segment skb_mac_gso_segment __skb_gso_segment skb_gso_segment validate_xmit_skb validate_xmit_skb_list sch_direct_xmit qdisc_restart __qdisc_run qdisc_run net_tx_action Fix: Add NAPI_GRO_CB(skb)->flush validation to the early-return check in skb_gro_receive_list(), matching the defensive programming pattern of skb_gro_receive().
References
Impacted products
Vendor Product Version
Linux Linux Version: 3a1296a38d0cf62bffb9a03c585cbd5dbf15d596
Version: 3a1296a38d0cf62bffb9a03c585cbd5dbf15d596
Version: 3a1296a38d0cf62bffb9a03c585cbd5dbf15d596
Version: 3a1296a38d0cf62bffb9a03c585cbd5dbf15d596
Version: 3a1296a38d0cf62bffb9a03c585cbd5dbf15d596
Version: 3a1296a38d0cf62bffb9a03c585cbd5dbf15d596
Version: 3a1296a38d0cf62bffb9a03c585cbd5dbf15d596
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          "value": "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)-\u003eflush may still be\nre-aggregated.\n\nThis allows already-GRO\u0027d 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 \u003c= 0 \u0026\u0026 i \u003e= nfrags \u0026\u0026 skb_headlen(list_skb) \u0026\u0026\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-\u003enext, 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)-\u003eflush validation to the early-return check in\nskb_gro_receive_list(), matching the defensive programming pattern of\nskb_gro_receive()."
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              "value": "AV:N - The bug is reached from the standard NAPI GRO receive path processing remotely originated TCP/IP packets (napi_gro_receive\u2192dev_gro_receive\u2192tcp_gro_receive\u2192skb_gro_receive_list), including tethering/NAT/forwarding scenarios where packets re-enter GRO on a second netdev after driver LRO or prior GRO aggregation.\nAC:L - An attacker can reliably trigger the bug by crafting a TCP stream through a forwarding host with rx-gro-list enabled, without races or victim-specific timing; the commit documents a deterministic tethering/forwarding repro where flush-marked frag_list skbs are re-aggregated and later crash skb_segment.\nPR:N - No local privileges or authentication are required; any remote peer that can send TCP traffic through a vulnerable forwarding/tethering/NAT Linux host can reach the GRO fraglist merge path, which performs no capability or credential checks on the receive path.\nUI:N - Exploitation requires only network-delivered packets and normal kernel forwarding/GRO processing; the victim does not need to open files, mount filesystems, click links, or perform any deliberate action beyond routine network operation.\nS:U - Impact is confined to kernel memory corruption and panic within the same host kernel security domain during packet GRO aggregation and subsequent segmentation on transmit; it does not cross VM, container, or IOMMU boundaries to affect a separate security authority.\nC:H - Double aggregation corrupts the skb frag_list chain (loops, dangling references, NULL/corrupted list_skb pointers), constituting kernel heap memory corruption that can be read during skb_segment processing and is classifiable as a high-impact info-disclosure primitive beyond a simple crash.\nI:H - Re-aggregating flush-marked skbs with existing frag_list corrupts skb linked-list structure and reference relationships in kernel memory, enabling potential control of subsequent skb metadata and write/control-flow primitives during GSO segmentation, not merely integrity-preserving packet drops.\nA:H - Corrupted frag_list state causes skb_segment to dereference a NULL or invalid list_skb via skb_headlen(), producing a kernel panic/oops on the transmit path (sch_direct_xmit/qdisc_run), fully denying availability of the affected system."
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    "datePublished": "2026-08-10T11:58:59.450Z",
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    "dateUpdated": "2026-10-19T20:58:52.839Z",
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Double aggregation corrupts the skb frag_list chain (loops, dangling references, NULL/corrupted list_skb pointers), constituting kernel heap memory corruption that can be read during skb_segment processing and is classifiable as a high-impact info-disclosure primitive beyond a simple crash.\\nI:H - Re-aggregating flush-marked skbs with existing frag_list corrupts skb linked-list structure and reference relationships in kernel memory, enabling potential control of subsequent skb metadata and write/control-flow primitives during GSO segmentation, not merely integrity-preserving packet drops.\\nA:H - Corrupted frag_list state causes skb_segment to dereference a NULL or invalid list_skb via skb_headlen(), producing a kernel panic/oops on the transmit path (sch_direct_xmit/qdisc_run), fully denying availability of the affected system.\"}]}], \"affected\": [{\"repo\": \"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git\", \"vendor\": \"Linux\", \"product\": \"Linux\", \"versions\": [{\"status\": \"affected\", \"version\": \"3a1296a38d0cf62bffb9a03c585cbd5dbf15d596\", \"lessThan\": \"7fc7e35212cf58c134310fb47566a844297ceae9\", \"versionType\": \"git\"}, {\"status\": \"affected\", \"version\": \"3a1296a38d0cf62bffb9a03c585cbd5dbf15d596\", \"lessThan\": \"d1fb23f8f794ac4683127bd49a6422bd87e0ac02\", \"versionType\": \"git\"}, {\"status\": \"affected\", \"version\": \"3a1296a38d0cf62bffb9a03c585cbd5dbf15d596\", \"lessThan\": \"db3e82da616f52e2b27e25e7be3fde2f2a5e54d6\", \"versionType\": \"git\"}, {\"status\": \"affected\", \"version\": \"3a1296a38d0cf62bffb9a03c585cbd5dbf15d596\", \"lessThan\": \"107e1a469f53a2a70874f3f12bf6fcd23925da1d\", \"versionType\": \"git\"}, {\"status\": \"affected\", \"version\": \"3a1296a38d0cf62bffb9a03c585cbd5dbf15d596\", \"lessThan\": \"a4dfd46cc8f08a29c6183794790547d0945f3d45\", \"versionType\": \"git\"}, {\"status\": \"affected\", \"version\": \"3a1296a38d0cf62bffb9a03c585cbd5dbf15d596\", \"lessThan\": \"fc0c0f7a207f0cd2d2aa725696c907f7d03af9e0\", \"versionType\": \"git\"}, {\"status\": \"affected\", \"version\": \"3a1296a38d0cf62bffb9a03c585cbd5dbf15d596\", \"lessThan\": \"e751256486d0ded20f5a9f9863467f1dce65142f\", \"versionType\": \"git\"}], \"programFiles\": [\"net/core/gro.c\"], \"defaultStatus\": \"unaffected\"}, {\"repo\": \"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git\", \"vendor\": \"Linux\", \"product\": \"Linux\", \"versions\": [{\"status\": \"affected\", \"version\": \"5.6\"}, {\"status\": \"unaffected\", \"version\": \"0\", \"lessThan\": \"5.6\", \"versionType\": \"semver\"}, {\"status\": \"unaffected\", \"version\": \"5.10.266\", \"versionType\": \"semver\", \"lessThanOrEqual\": \"5.10.*\"}, {\"status\": \"unaffected\", \"version\": \"6.1.184\", \"versionType\": \"semver\", \"lessThanOrEqual\": \"6.1.*\"}, {\"status\": \"unaffected\", \"version\": \"6.6.153\", \"versionType\": \"semver\", \"lessThanOrEqual\": \"6.6.*\"}, {\"status\": \"unaffected\", \"version\": \"6.12.101\", \"versionType\": \"semver\", \"lessThanOrEqual\": \"6.12.*\"}, {\"status\": \"unaffected\", \"version\": \"6.18.42\", \"versionType\": \"semver\", \"lessThanOrEqual\": \"6.18.*\"}, {\"status\": \"unaffected\", \"version\": \"7.1.6\", \"versionType\": \"semver\", \"lessThanOrEqual\": \"7.1.*\"}, {\"status\": \"unaffected\", \"version\": \"7.2\", \"versionType\": \"original_commit_for_fix\", \"lessThanOrEqual\": \"*\"}], \"programFiles\": [\"net/core/gro.c\"], \"defaultStatus\": \"affected\"}], \"references\": [{\"url\": \"https://git.kernel.org/stable/c/7fc7e35212cf58c134310fb47566a844297ceae9\"}, {\"url\": \"https://git.kernel.org/stable/c/d1fb23f8f794ac4683127bd49a6422bd87e0ac02\"}, {\"url\": \"https://git.kernel.org/stable/c/db3e82da616f52e2b27e25e7be3fde2f2a5e54d6\"}, {\"url\": \"https://git.kernel.org/stable/c/107e1a469f53a2a70874f3f12bf6fcd23925da1d\"}, {\"url\": \"https://git.kernel.org/stable/c/a4dfd46cc8f08a29c6183794790547d0945f3d45\"}, {\"url\": \"https://git.kernel.org/stable/c/fc0c0f7a207f0cd2d2aa725696c907f7d03af9e0\"}, {\"url\": \"https://git.kernel.org/stable/c/e751256486d0ded20f5a9f9863467f1dce65142f\"}], \"x_generator\": {\"engine\": \"bippy-1.2.0\"}, \"descriptions\": [{\"lang\": \"en\", \"value\": \"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)-\u003eflush may still be\\nre-aggregated.\\n\\nThis allows already-GRO\u0027d 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 \u003c= 0 \u0026\u0026 i \u003e= nfrags \u0026\u0026 skb_headlen(list_skb) \u0026\u0026\\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-\u003enext, 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)-\u003eflush validation to the early-return check in\\nskb_gro_receive_list(), matching the defensive programming pattern of\\nskb_gro_receive().\"}], \"cpeApplicability\": [{\"nodes\": [{\"negate\": false, \"cpeMatch\": [{\"criteria\": \"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*\", \"vulnerable\": true, \"versionEndExcluding\": \"5.10.266\", \"versionStartIncluding\": \"5.6\"}, {\"criteria\": \"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*\", \"vulnerable\": true, \"versionEndExcluding\": \"6.1.184\", \"versionStartIncluding\": \"5.6\"}, {\"criteria\": \"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*\", \"vulnerable\": true, \"versionEndExcluding\": \"6.6.153\", \"versionStartIncluding\": \"5.6\"}, {\"criteria\": \"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*\", \"vulnerable\": true, \"versionEndExcluding\": \"6.12.101\", \"versionStartIncluding\": \"5.6\"}, {\"criteria\": \"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*\", \"vulnerable\": true, \"versionEndExcluding\": \"6.18.42\", \"versionStartIncluding\": \"5.6\"}, {\"criteria\": \"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*\", \"vulnerable\": true, \"versionEndExcluding\": \"7.1.6\", \"versionStartIncluding\": \"5.6\"}, {\"criteria\": \"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*\", \"vulnerable\": true, \"versionEndExcluding\": \"7.2\", \"versionStartIncluding\": \"5.6\"}], \"operator\": \"OR\"}]}], \"providerMetadata\": {\"orgId\": \"416baaa9-dc9f-4396-8d5f-8c081fb06d67\", \"shortName\": \"Linux\", \"dateUpdated\": \"2026-08-23T12:45:54.689Z\"}}}",
      "cveMetadata": "{\"cveId\": \"CVE-2026-68136\", \"state\": \"PUBLISHED\", \"dateUpdated\": \"2026-10-19T20:58:52.839Z\", \"dateReserved\": \"2026-07-30T09:28:09.370Z\", \"assignerOrgId\": \"416baaa9-dc9f-4396-8d5f-8c081fb06d67\", \"datePublished\": \"2026-08-10T11:58:59.450Z\", \"assignerShortName\": \"Linux\"}",
      "dataType": "CVE_RECORD",
      "dataVersion": "5.2"
    }
  }
}


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