CVE-2026-80725 (GCVE-0-2026-80725)
Vulnerability from cvelistv5
Published
2026-08-29 06:39
Modified
2026-08-29 06:40
Severity ?
VLAI Severity ?
EPSS score ?
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.
References
Impacted products
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"descriptions": [
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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."
}
],
"providerMetadata": {
"dateUpdated": "2026-08-29T06:40:30.300Z",
"orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
"shortName": "Linux"
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"references": [
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"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"
}
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"title": "net: gro: properly validate BIG TCP aggregation criteria",
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"cveId": "CVE-2026-80725",
"datePublished": "2026-08-29T06:39:35.212Z",
"dateReserved": "2026-08-26T14:34:25.789Z",
"dateUpdated": "2026-08-29T06:40:30.300Z",
"state": "PUBLISHED"
},
"dataType": "CVE_RECORD",
"dataVersion": "5.2"
}
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Sightings
| Author | Source | Type | Date |
|---|
Nomenclature
- Seen: The vulnerability was mentioned, discussed, or seen somewhere by the user.
- Confirmed: The vulnerability is confirmed from an analyst perspective.
- Published Proof of Concept: A public proof of concept is available for this vulnerability.
- Exploited: This vulnerability was exploited and seen by the user reporting the sighting.
- Patched: This vulnerability was successfully patched by the user reporting the sighting.
- Not exploited: This vulnerability was not exploited or seen by the user reporting the sighting.
- Not confirmed: The user expresses doubt about the veracity of the vulnerability.
- Not patched: This vulnerability was not successfully patched by the user reporting the sighting.
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