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CVE-2026-80725 (GCVE-0-2026-80725)

Vulnerability from cvelistv5 – Published: 2026-08-29 06:39 – Updated: 2026-09-04 04:58
VLAI
Title
net: gro: properly validate BIG TCP aggregation criteria
Summary
In the Linux kernel, the following vulnerability has been resolved: net: gro: properly validate BIG TCP aggregation criteria When GRO attempts to aggregate packets beyond GRO_LEGACY_MAX_SIZE (64KB), BIG TCP should only be permitted for plain IPv4 TCP and plain IPv6 TCP (with sufficient MAC header room to insert the temporary HBH jumbo header). However, commit b1a78b9b9886 ("net: add support for ipv4 big tcp") loosened the check in skb_gro_receive(), leading to several issues: 1. skb_gro_receive() checked skb_headroom(p) instead of the actual space before the MAC header (p->mac_header). Because skb_headroom(p) includes mac_len, crafted frames (e.g. injected via AF_PACKET) can pass the check with p->mac_header < 8 bytes. When ipv6_gro_complete() inserts the temporary HBH jumbo header, the memmove() starts before skb->head, causing an out-of-bounds write and wrapping skb->mac_header. 2. It allowed non-IP protocols such as software VLAN (ETH_P_8021Q / ETH_P_8021AD) to aggregate beyond 64KB because p->protocol != ETH_P_IPV6 was true. 3. It checked p->encapsulation instead of NAPI_GRO_CB(skb)->encap_mark, allowing encapsulated flows (e.g. SIT / IPv6-in-IPv4) to aggregate beyond 64KB. Fix skb_gro_receive() to strictly enforce: - NAPI_GRO_CB(skb)->proto == IPPROTO_TCP - Not encapsulated (!NAPI_GRO_CB(skb)->encap_mark && !p->encapsulation) - Protocol must be either ETH_P_IP or ETH_P_IPV6 - If ETH_P_IPV6, p->mac_header must be at least sizeof(struct hop_jumbo_hdr) Returning -E2BIG from skb_gro_receive() ensures that packets which cannot become BIG TCP are cleanly flushed at <= 64KB and delivered intact without dropping. This issue does not exist in mainline (7.0+) because the subsystem was rewritten in commit 81be30c1f5f2 ("net/ipv6: Drop HBH for BIG TCP on RX side"), making this fix relevant only for older stable branches like 6.18.y.
Severity
9.8 (Critical)
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
Assigner
References
Impacted products
Vendor Product Version CPE status
Linux Linux Affected: 0fe79f28bfaf73b66b7b1562d2468f94aa03bd12 , < 37a5dcd6837fc2afc44a7bc3ed8af4e983783d46 (git)
Affected: 0fe79f28bfaf73b66b7b1562d2468f94aa03bd12 , < e907bf694ed55bdfe421be99dba35751a655df25 (git)
Affected: 0fe79f28bfaf73b66b7b1562d2468f94aa03bd12 , < 03cb8cc2961f5f781d12e903782cb3815ed84b1c (git)
Affected: 0fe79f28bfaf73b66b7b1562d2468f94aa03bd12 , < 3ce832e2bd431d0c12ba525ed73ad8fbc4191da5 (git)
Affected: 0fe79f28bfaf73b66b7b1562d2468f94aa03bd12 , < 81be30c1f5f2bffda1f04c0efd0746af10b9643a (git)
guessed Create a notification for this product.
Linux Linux Affected: 5.19
Unaffected: 0 , < 5.19 (semver)
Unaffected: 6.1.185 , ≤ 6.1.* (semver)
Unaffected: 6.6.154 , ≤ 6.6.* (semver)
Unaffected: 6.12.106 , ≤ 6.12.* (semver)
Unaffected: 6.18.47 , ≤ 6.18.* (semver)
Unaffected: 7.0 , ≤ * (original_commit_for_fix)
guessed Create a notification for this product.
Show details on NVD website
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          "lang": "en",
          "value": "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 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-\u003emac_header). Because skb_headroom(p) includes\n   mac_len, crafted frames (e.g. injected via AF_PACKET) can pass the check\n   with p-\u003emac_header \u003c 8 bytes. When ipv6_gro_complete() inserts the\n   temporary HBH jumbo header, the memmove() starts before skb-\u003ehead,\n   causing an out-of-bounds write and wrapping skb-\u003emac_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-\u003eprotocol != ETH_P_IPV6 was true.\n3. It checked p-\u003eencapsulation instead of NAPI_GRO_CB(skb)-\u003eencap_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)-\u003eproto == IPPROTO_TCP\n- Not encapsulated (!NAPI_GRO_CB(skb)-\u003eencap_mark \u0026\u0026 !p-\u003eencapsulation)\n- Protocol must be either ETH_P_IP or ETH_P_IPV6\n- If ETH_P_IPV6, p-\u003emac_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 \u003c= 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."
        }
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            "version": "3.1"
          },
          "scenarios": [
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              "lang": "en",
              "value": "AV:N - The flaw is in skb_gro_receive() on the netdev NAPI GRO ingress path (netif_receive_skb\u2192napi_gro_receive\u2192dev_gro_receive\u2192tcp/ipv6 gro handlers); remote peers can deliver crafted in-flow TCP streams to internet-facing interfaces without local access.\nAC:L - On Big TCP deployments with gro_max_size\u003e64KB, an attacker reliably coalesces past GRO_LEGACY_MAX_SIZE by sending many same-flow TCP segments; AF_PACKET injection also gives deterministic header layout control without races or victim-dependent heap layout.\nPR:N - RX GRO runs in softirq on all received packets before socket authentication; no target credentials or capabilities are required. Elevated gro_max_size is an admin tuning prerequisite of the Big TCP server class, not an attacker privilege.\nUI:N - Packet reception and GRO aggregation are automatic kernel network-stack processing triggered solely by attacker-sent traffic; no victim mount, file open, or other interaction is required.\nS:U - Impact is kernel skb/heap memory corruption within the host kernel security authority; exploitation does not cross VM, container, or IOMMU boundaries that would warrant scope-changed scoring.\nC:H - When undersized mac_header room passes the broken skb_headroom check, ipv6_gro_complete() memmove() for the temporary HBH jumbo header writes before skb-\u003ehead, corrupting adjacent kernel memory and enabling information disclosure from attacker-influenced out-of-bounds writes.\nI:H - The same invalid BIG TCP aggregation drives attacker-controlled memmove/header corruption that wraps skb-\u003emac_header, yielding an out-of-bounds write primitive suitable for heap object corruption, control-flow hijacking, and local privilege escalation.\nA:H - The defective memmove or invalid \u003e64KB aggregation on disallowed VLAN, encapsulated, or malformed flows can oops or panic the kernel during GRO completion, and a remote attacker can trigger this repeatedly to deny service."
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      "providerMetadata": {
        "dateUpdated": "2026-09-04T04:58:15.396Z",
        "orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
        "shortName": "Linux"
      },
      "references": [
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    "cveId": "CVE-2026-80725",
    "datePublished": "2026-08-29T06:39:35.212Z",
    "dateReserved": "2026-08-26T14:34:25.789Z",
    "dateUpdated": "2026-09-04T04:58:15.396Z",
    "state": "PUBLISHED"
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  "dataVersion": "5.2",
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      "date": "2026-09-18",
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      "percentile": "0.38822"
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        "cveTags": [],
        "descriptions": [
          {
            "lang": "en",
            "value": "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 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-\u003emac_header). Because skb_headroom(p) includes\n   mac_len, crafted frames (e.g. injected via AF_PACKET) can pass the check\n   with p-\u003emac_header \u003c 8 bytes. When ipv6_gro_complete() inserts the\n   temporary HBH jumbo header, the memmove() starts before skb-\u003ehead,\n   causing an out-of-bounds write and wrapping skb-\u003emac_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-\u003eprotocol != ETH_P_IPV6 was true.\n3. It checked p-\u003eencapsulation instead of NAPI_GRO_CB(skb)-\u003eencap_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)-\u003eproto == IPPROTO_TCP\n- Not encapsulated (!NAPI_GRO_CB(skb)-\u003eencap_mark \u0026\u0026 !p-\u003eencapsulation)\n- Protocol must be either ETH_P_IP or ETH_P_IPV6\n- If ETH_P_IPV6, p-\u003emac_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 \u003c= 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."
          }
        ],
        "id": "CVE-2026-80725",
        "lastModified": "2026-09-04T05:17:13.230",
        "metrics": {
          "cvssMetricV31": [
            {
              "cvssData": {
                "attackComplexity": "LOW",
                "attackVector": "NETWORK",
                "availabilityImpact": "HIGH",
                "baseScore": 9.8,
                "baseSeverity": "CRITICAL",
                "confidentialityImpact": "HIGH",
                "integrityImpact": "HIGH",
                "privilegesRequired": "NONE",
                "scope": "UNCHANGED",
                "userInteraction": "NONE",
                "vectorString": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H",
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              "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
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        "published": "2026-08-29T07:16:54.573",
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            "url": "https://git.kernel.org/stable/c/03cb8cc2961f5f781d12e903782cb3815ed84b1c"
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            "url": "https://git.kernel.org/stable/c/e907bf694ed55bdfe421be99dba35751a655df25"
          }
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        "sourceIdentifier": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
        "vulnStatus": "Received"
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    "redhat_vex": {
      "aggregate_severity": "Important",
      "current_release_date": "2026-09-04T05:27:50+00:00",
      "cve": "CVE-2026-80725",
      "id": "CVE-2026-80725",
      "initial_release_date": "2026-08-29T00:00:00+00:00",
      "product_status:known_affected": "185",
      "product_status:known_not_affected": "90",
      "source": "Red Hat CSAF VEX",
      "status": "final",
      "title": "kernel: net: gro: properly validate BIG TCP aggregation criteria",
      "url": "https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-80725.json",
      "version": "3"
    },
    "suse_vex": {
      "aggregate_severity": "important",
      "current_release_date": "2026-09-15T01:09:23Z",
      "cve": "CVE-2026-80725",
      "id": "CVE-2026-80725",
      "initial_release_date": "2026-08-30T01:33:15Z",
      "product_status:known_affected": "114",
      "product_status:known_not_affected": "239",
      "source": "SUSE CSAF VEX",
      "status": "interim",
      "title": "SUSE CVE CVE-2026-80725",
      "url": "https://ftp.suse.com/pub/projects/security/csaf-vex/cve-2026-80725.json",
      "version": "5"
    }
  }
}



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