net: gro: fix double aggregation of flush-marked skbs

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().

Timeline

Scores

EPSS (exploitation in 30 days)

0.54% · top 54% of all CVEs (11 Nov 2026)

CISA SSVC

Exploitation: none · Automatable: yes · Technical impact: total

The list uses the assigner's score when there is one, then CISA's, then NVD's: Critical 9.8.

Affected products

• Linux · Linux

  • affected 3a1296a38d0cf62bffb9a03c585cbd5dbf15d596 – < 7fc7e35212cf58c134310fb47566a844297ceae9
  • affected 3a1296a38d0cf62bffb9a03c585cbd5dbf15d596 – < d1fb23f8f794ac4683127bd49a6422bd87e0ac02
  • affected 3a1296a38d0cf62bffb9a03c585cbd5dbf15d596 – < db3e82da616f52e2b27e25e7be3fde2f2a5e54d6
  • affected 3a1296a38d0cf62bffb9a03c585cbd5dbf15d596 – < 107e1a469f53a2a70874f3f12bf6fcd23925da1d
  • affected 3a1296a38d0cf62bffb9a03c585cbd5dbf15d596 – < a4dfd46cc8f08a29c6183794790547d0945f3d45
  • affected 3a1296a38d0cf62bffb9a03c585cbd5dbf15d596 – < fc0c0f7a207f0cd2d2aa725696c907f7d03af9e0
  • affected 3a1296a38d0cf62bffb9a03c585cbd5dbf15d596 – < e751256486d0ded20f5a9f9863467f1dce65142f

• Linux · Linux

  • affected 5.6
  • unaffected < 5.6
  • unaffected 5.10.266 – ≤ 5.10.*
  • unaffected 6.1.184 – ≤ 6.1.*
  • unaffected 6.6.153 – ≤ 6.6.*
  • unaffected 6.12.101 – ≤ 6.12.*
  • unaffected 6.18.42 – ≤ 6.18.*
  • unaffected 7.1.6 – ≤ 7.1.*
  • unaffected 7.2 – ≤ *

Sources

The same CVE in the primary databases and aggregators, to check against.

• CVE.org record (opens in a new tab)
• CVE List JSON (GitHub) (opens in a new tab)
• NVD (opens in a new tab)
• FIRST EPSS (opens in a new tab)
• EUVD EUVD-2026-55517 (opens in a new tab)
• OSV.dev (opens in a new tab)
• GitHub Advisories (opens in a new tab)
• CIRCL Vulnerability-Lookup (opens in a new tab)

Badge for a README or a ticket

[![CVE-2026-68136](https://cveledger.app/badge/CVE-2026-68136.svg)](https://cveledger.app/cve/CVE-2026-68136)

Record last updated 19 Oct 2026, 20:58 UTC.