CVE-2026-80725Critical· 9.8▾ Midnight

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…

▾ Midnight zone — Critical, or high with PoC / in-the-wild

Depth score54/ 100 · Moderate

impact 53.9 · likelihood 0.1 · exploitation 0

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Proof of concept

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Published

Aug 29, 2026

Updated

Oct 16, 2026

CVSS

9.8

Vendor

Linux

Product

Linux

CWE

—

Depth score

54 · Moderate

EPSS

0.46% · p40

Platforms

—

Source

NVD

Vector

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H

CISA SSVC

decided 2026-10-16

Exploitation: none
Automatable: yes
Technical impact: total

Stakeholder-Specific Vulnerability Categorization from CISA's ADP record at CVE.org: whether exploitation is observed, whether an attack can be automated, and how much of the system is at stake.

EPSS history

Exploit-prediction probability, daily snapshots since Oct 16.

0.5% → 0.5%

Timeline

Disclosure to exploitation, from the record and what we observed since indexing it.

3 events · 48 days

Aug 29, 2026Published
Disclosed via NVD
Oct 16, 2026Record revised
Last analysed / modified upstream
Oct 16, 2026EPSS first tracked
0.5%

Linux #nvd #cve.org

Affected

Linux >= 0fe79f28bfaf73b66b7b1562d2468f94aa03bd12 < 37a5dcd6837fc2afc44a7bc3ed8af4e983783d46
Linux >= 0fe79f28bfaf73b66b7b1562d2468f94aa03bd12 < e907bf694ed55bdfe421be99dba35751a655df25
Linux >= 0fe79f28bfaf73b66b7b1562d2468f94aa03bd12 < 03cb8cc2961f5f781d12e903782cb3815ed84b1c
Linux >= 0fe79f28bfaf73b66b7b1562d2468f94aa03bd12 < 3ce832e2bd431d0c12ba525ed73ad8fbc4191da5
Linux >= 0fe79f28bfaf73b66b7b1562d2468f94aa03bd12 < 81be30c1f5f2bffda1f04c0efd0746af10b9643a
Linux 5.19

Full technical detail▾

Overview

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:

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.
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.
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.

Remediation

Refer to the linked advisories for vendor-supplied fixes and affected version ranges.

References

Related vulnerabilities

Connected by shared product, vendor, weakness, or advisory.

#nvd#cve.org

▾ Midnight zone — Critical, or high with PoC / in-the-wild

Depth score54/ 100 · Moderate

impact 53.9 · likelihood 0.1 · exploitation 0

Overview

In the Linux kernel, the following vulnerability has been resolved:

net: gro: properly validate BIG TCP aggregation criteria

However, commit b1a78b9b9886 ("net: add support for ipv4 big tcp") loosened the check in skb_gro_receive(), leading to several issues:

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.

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.

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.