{
  "schema_version": "1.6.1",
  "id": "RPI-CVE-2026-45859",
  "modified": "2026-10-09T11:39:44Z",
  "upstream": [
    "CVE-2026-45859"
  ],
  "published": "2026-05-27T12:19:29Z",
  "summary": "netfilter: nfnetlink_queue: do shared-unconfirmed check before segmentation",
  "details": "In the Linux kernel, the following vulnerability has been resolved:\n\nnetfilter: nfnetlink_queue: do shared-unconfirmed check before segmentation\n\nUlrich reports a regression with nfqueue:\n\nIf an application did not set the 'F_GSO' capability flag and a gso\npacket with an unconfirmed nf_conn entry is received all packets are\nnow dropped instead of queued, because the check happens after\nskb_gso_segment().  In that case, we did have exclusive ownership\nof the skb and its associated conntrack entry.  The elevated use\ncount is due to skb_clone happening via skb_gso_segment().\n\nMove the check so that its peformed vs. the aggregated packet.\n\nThen, annotate the individual segments except the first one so we\ncan do a 2nd check at reinject time.\n\nFor the normal case, where userspace does in-order reinjects, this avoids\npacket drops: first reinjected segment continues traversal and confirms\nentry, remaining segments observe the confirmed entry.\n\nWhile at it, simplify nf_ct_drop_unconfirmed(): We only care about\nunconfirmed entries with a refcnt > 1, there is no need to special-case\ndying entries.\n\nThis only happens with UDP.  With TCP, the only unconfirmed packet will\nbe the TCP SYN, those aren't aggregated by GRO.\n\nNext patch adds a udpgro test case to cover this scenario.",
  "severity": [
    {
      "type": "CVSS_V3",
      "score": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H"
    }
  ],
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            "upstream_version": "6.12.62",
            "assessment": "commit ancestry (strak rule)",
            "upstream_fixed": "6.12.75"
          }
        }
      }
    }
  ],
  "references": [
    {
      "type": "ADVISORY",
      "url": "https://www.cve.org/CVERecord?id=CVE-2026-45859"
    },
    {
      "type": "FIX",
      "url": "https://git.kernel.org/stable/c/79b713ef4261a8ead96af4703f89d0b5f25532e2"
    },
    {
      "type": "FIX",
      "url": "https://git.kernel.org/stable/c/23901aa6b8a2f294c4b774436b4691f3ff863a8f"
    },
    {
      "type": "FIX",
      "url": "https://git.kernel.org/stable/c/b740e7ddd7ca0dbfeafca3f5e52717206cf28524"
    },
    {
      "type": "FIX",
      "url": "https://git.kernel.org/stable/c/207b3ebacb6113acaaec0d171d5307032c690004"
    }
  ],
  "database_specific": {
    "source": "https://git.kernel.org/pub/scm/linux/security/vulns.git",
    "upstream_modified": "2026-08-05T13:16:28Z",
    "severity": {
      "source": "kernel CNA",
      "cvss_v3_score": 7.5,
      "cvss_v3_severity": "High",
      "scenario": "AV:N - The vulnerable nfnetlink_queue path processes packets that hit an NFQUEUE netfilter verdict; GRO-aggregated UDP traffic received from the network reaches it, so the dropping condition is triggered by remote network packets.\nAC:L - Once an nfqueue without F_GSO exists, an attacker reliably triggers the drop by sending a UDP burst that GRO coalesces into a GSO skb for a new (unconfirmed) flow; no uncontrollable condition is required.\nPR:N - Triggering the condition requires only sending network traffic to the host; no authentication or privileges are needed by the remote sender.\nUI:N - The packet drop occurs automatically during kernel packet processing with no victim interaction.\nS:U - The impact is confined to the kernel's own network packet processing; no security boundary is crossed.\nC:N - The bug only causes packets to be dropped; no kernel memory is read or disclosed.\nI:N - No data is modified or written; dropped packets are simply not delivered, which is an availability rather than integrity effect.\nA:H - All GSO-aggregated UDP packets of new (unconfirmed) conntrack flows are dropped on a non-F_GSO nfqueue, denying establishment/processing of those new flows \u2014 a sustained, network-triggerable denial of that traffic class."
    }
  }
}