Vulnerability-Lookup

GHSA-Q4JF-GP35-367G

Vulnerability from github – Published: 2026-06-24 18:32 – Updated: 2026-07-04 12:30

Details

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

sctp: disable BH before calling udp_tunnel_xmit_skb()

udp_tunnel_xmit_skb() / udp_tunnel6_xmit_skb() are expected to run with BH disabled. After commit 6f1a9140ecda ("add xmit recursion limit to tunnel xmit functions"), on the path:

udp(6)_tunnel_xmit_skb() -> ip(6)tunnel_xmit()

dev_xmit_recursion_inc()/dec() must stay balanced on the same CPU.

Without local_bh_disable(), the context may move between CPUs, which can break the inc/dec pairing. This may lead to incorrect recursion level detection and cause packets to be dropped in ip(6)_tunnel_xmit() or __dev_queue_xmit().

Fix it by disabling BH around both IPv4 and IPv6 SCTP UDP xmit paths.

In my testing, after enabling the SCTP over UDP:

# ip net exec ha sysctl -w net.sctp.udp_port=9899 # ip net exec ha sysctl -w net.sctp.encap_port=9899 # ip net exec hb sysctl -w net.sctp.udp_port=9899 # ip net exec hb sysctl -w net.sctp.encap_port=9899

# ip net exec ha iperf3 -s

without this patch:

# ip net exec hb iperf3 -c 192.168.0.1 --sctp [ 5] 0.00-10.00 sec 37.2 MBytes 31.2 Mbits/sec sender [ 5] 0.00-10.00 sec 37.1 MBytes 31.1 Mbits/sec receiver

with this patch:

# ip net exec hb iperf3 -c 192.168.0.1 --sctp [ 5] 0.00-10.00 sec 3.14 GBytes 2.69 Gbits/sec sender [ 5] 0.00-10.00 sec 3.14 GBytes 2.69 Gbits/sec receiver

Severity

7.5 (High)


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

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{
  "affected": [],
  "aliases": [
    "CVE-2026-53070"
  ],
  "database_specific": {
    "cwe_ids": [],
    "github_reviewed": false,
    "github_reviewed_at": null,
    "nvd_published_at": "2026-06-24T17:17:20Z",
    "severity": "HIGH"
  },
  "details": "In the Linux kernel, the following vulnerability has been resolved:\n\nsctp: disable BH before calling udp_tunnel_xmit_skb()\n\nudp_tunnel_xmit_skb() / udp_tunnel6_xmit_skb() are expected to run with\nBH disabled.  After commit 6f1a9140ecda (\"add xmit recursion limit to\ntunnel xmit functions\"), on the path:\n\n  udp(6)_tunnel_xmit_skb() -\u003e ip(6)tunnel_xmit()\n\ndev_xmit_recursion_inc()/dec() must stay balanced on the same CPU.\n\nWithout local_bh_disable(), the context may move between CPUs, which can\nbreak the inc/dec pairing. This may lead to incorrect recursion level\ndetection and cause packets to be dropped in ip(6)_tunnel_xmit() or\n__dev_queue_xmit().\n\nFix it by disabling BH around both IPv4 and IPv6 SCTP UDP xmit paths.\n\nIn my testing, after enabling the SCTP over UDP:\n\n  # ip net exec ha sysctl -w net.sctp.udp_port=9899\n  # ip net exec ha sysctl -w net.sctp.encap_port=9899\n  # ip net exec hb sysctl -w net.sctp.udp_port=9899\n  # ip net exec hb sysctl -w net.sctp.encap_port=9899\n\n  # ip net exec ha iperf3 -s\n\n- without this patch:\n\n  # ip net exec hb iperf3 -c 192.168.0.1 --sctp\n  [  5]   0.00-10.00  sec  37.2 MBytes  31.2 Mbits/sec  sender\n  [  5]   0.00-10.00  sec  37.1 MBytes  31.1 Mbits/sec  receiver\n\n- with this patch:\n\n  # ip net exec hb iperf3 -c 192.168.0.1 --sctp\n  [  5]   0.00-10.00  sec  3.14 GBytes  2.69 Gbits/sec  sender\n  [  5]   0.00-10.00  sec  3.14 GBytes  2.69 Gbits/sec  receiver",
  "id": "GHSA-q4jf-gp35-367g",
  "modified": "2026-07-04T12:30:28Z",
  "published": "2026-06-24T18:32:45Z",
  "references": [
    {
      "type": "ADVISORY",
      "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-53070"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/0de7db2eb27e82b983157016fa604b1ba664ae5f"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/2cd7e6971fc2787408ceef17906ea152791448cf"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/790093245e35040c2adb15f48970020425aa3f47"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/be3bfcb34bda04f6a350710db471d4133f950f2c"
    }
  ],
  "schema_version": "1.4.0",
  "severity": [
    {
      "score": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H",
      "type": "CVSS_V3"
    }
  ]
}

CVE-2026-53070 (GCVE-0-2026-53070)

Vulnerability from cvelistv5 – Published: 2026-06-24 16:30 – Updated: 2026-08-05 12:33

Title

sctp: disable BH before calling udp_tunnel_xmit_skb()

Summary

In the Linux kernel, the following vulnerability has been resolved: sctp: disable BH before calling udp_tunnel_xmit_skb() udp_tunnel_xmit_skb() / udp_tunnel6_xmit_skb() are expected to run with BH disabled. After commit 6f1a9140ecda ("add xmit recursion limit to tunnel xmit functions"), on the path: udp(6)_tunnel_xmit_skb() -> ip(6)tunnel_xmit() dev_xmit_recursion_inc()/dec() must stay balanced on the same CPU. Without local_bh_disable(), the context may move between CPUs, which can break the inc/dec pairing. This may lead to incorrect recursion level detection and cause packets to be dropped in ip(6)_tunnel_xmit() or __dev_queue_xmit(). Fix it by disabling BH around both IPv4 and IPv6 SCTP UDP xmit paths. In my testing, after enabling the SCTP over UDP: # ip net exec ha sysctl -w net.sctp.udp_port=9899 # ip net exec ha sysctl -w net.sctp.encap_port=9899 # ip net exec hb sysctl -w net.sctp.udp_port=9899 # ip net exec hb sysctl -w net.sctp.encap_port=9899 # ip net exec ha iperf3 -s - without this patch: # ip net exec hb iperf3 -c 192.168.0.1 --sctp [ 5] 0.00-10.00 sec 37.2 MBytes 31.2 Mbits/sec sender [ 5] 0.00-10.00 sec 37.1 MBytes 31.1 Mbits/sec receiver - with this patch: # ip net exec hb iperf3 -c 192.168.0.1 --sctp [ 5] 0.00-10.00 sec 3.14 GBytes 2.69 Gbits/sec sender [ 5] 0.00-10.00 sec 3.14 GBytes 2.69 Gbits/sec receiver

Severity

7.5 (High)


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

Assigner

Linux mitre root

References

4 references

URL	Tags
https://git.kernel.org/stable/c/be3bfcb34bda04f6a…
https://git.kernel.org/stable/c/0de7db2eb27e82b98…
https://git.kernel.org/stable/c/790093245e35040c2…
https://git.kernel.org/stable/c/2cd7e6971fc278740…

Impacted products

2 products

Vendor	Product	Version
Linux	Linux	Affected: 046c052b475e7119b6a30e3483e2888fc606a2f8 , < be3bfcb34bda04f6a350710db471d4133f950f2c (git) Affected: 046c052b475e7119b6a30e3483e2888fc606a2f8 , < 0de7db2eb27e82b983157016fa604b1ba664ae5f (git) Affected: 046c052b475e7119b6a30e3483e2888fc606a2f8 , < 790093245e35040c2adb15f48970020425aa3f47 (git) Affected: 046c052b475e7119b6a30e3483e2888fc606a2f8 , < 2cd7e6971fc2787408ceef17906ea152791448cf (git)
Linux	Linux	Affected: 5.11 Unaffected: 0 , < 5.11 (semver) Unaffected: 6.12.95 , ≤ 6.12.* (semver) Unaffected: 6.18.37 , ≤ 6.18.* (semver) Unaffected: 7.0.10 , ≤ 7.0.* (semver) Unaffected: 7.1 , ≤ * (original_commit_for_fix)

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JSON

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            "net/sctp/ipv6.c",
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            },
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              "versionType": "git"
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            "net/sctp/protocol.c"
          ],
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          "versions": [
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              "version": "5.11"
            },
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              "status": "unaffected",
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              "versionType": "semver"
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            }
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        }
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      "cpeApplicability": [
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          "nodes": [
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                  "versionEndExcluding": "6.12.95",
                  "versionStartIncluding": "5.11",
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                },
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                },
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      "descriptions": [
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          "lang": "en",
          "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nsctp: disable BH before calling udp_tunnel_xmit_skb()\n\nudp_tunnel_xmit_skb() / udp_tunnel6_xmit_skb() are expected to run with\nBH disabled.  After commit 6f1a9140ecda (\"add xmit recursion limit to\ntunnel xmit functions\"), on the path:\n\n  udp(6)_tunnel_xmit_skb() -\u003e ip(6)tunnel_xmit()\n\ndev_xmit_recursion_inc()/dec() must stay balanced on the same CPU.\n\nWithout local_bh_disable(), the context may move between CPUs, which can\nbreak the inc/dec pairing. This may lead to incorrect recursion level\ndetection and cause packets to be dropped in ip(6)_tunnel_xmit() or\n__dev_queue_xmit().\n\nFix it by disabling BH around both IPv4 and IPv6 SCTP UDP xmit paths.\n\nIn my testing, after enabling the SCTP over UDP:\n\n  # ip net exec ha sysctl -w net.sctp.udp_port=9899\n  # ip net exec ha sysctl -w net.sctp.encap_port=9899\n  # ip net exec hb sysctl -w net.sctp.udp_port=9899\n  # ip net exec hb sysctl -w net.sctp.encap_port=9899\n\n  # ip net exec ha iperf3 -s\n\n- without this patch:\n\n  # ip net exec hb iperf3 -c 192.168.0.1 --sctp\n  [  5]   0.00-10.00  sec  37.2 MBytes  31.2 Mbits/sec  sender\n  [  5]   0.00-10.00  sec  37.1 MBytes  31.1 Mbits/sec  receiver\n\n- with this patch:\n\n  # ip net exec hb iperf3 -c 192.168.0.1 --sctp\n  [  5]   0.00-10.00  sec  3.14 GBytes  2.69 Gbits/sec  sender\n  [  5]   0.00-10.00  sec  3.14 GBytes  2.69 Gbits/sec  receiver"
        }
      ],
      "metrics": [
        {
          "cvssV3_1": {
            "baseScore": 7.5,
            "baseSeverity": "HIGH",
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            "version": "3.1"
          },
          "scenarios": [
            {
              "lang": "en",
              "value": "AV:N - SCTP-over-UDP transmit is reachable from network-facing SCTP endpoints when received packets or application-level requests cause replies through the SCTP output path. A remote peer can trigger the affected UDP-encapsulated transmit path in a reasonable SCTP service deployment.\nAC:L - The bug is triggered by repeatedly causing SCTP-over-UDP transmission in process/backlog context where BH is not disabled. Although CPU migration/preemption timing is involved, the attacker can drive repeated transmissions and the higher-severity choice is AC:L.\nPR:N - A remote SCTP peer does not need local credentials or kernel privileges to send packets to an SCTP-over-UDP service and induce responses. Local setup of SCTP-over-UDP may require configuration, but exploitation of an exposed configured service is unauthenticated.\nUI:N - No victim user action is required once an SCTP-over-UDP endpoint is exposed. The attacker only sends network traffic.\nS:U - The impact remains within the kernel networking stack and host network availability. This is not a VM escape, IOMMU bypass, or cross-authority boundary violation.\nC:N - The bug corrupts transmit recursion accounting, not packet contents or attacker-readable memory. I found no evidence of an information disclosure primitive.\nI:N - The issue causes incorrect recursion detection and packet drops, not arbitrary writes, control-flow hijack, or attacker-controlled data modification. The only modified state is internal transmit recursion accounting.\nA:H - Unbalanced per-CPU transmit recursion counters can become stale or underflowed, causing false recursion-limit detection and persistent packet drops in tunnel or device transmit paths. Repeated triggering can deny network availability for affected SCTP-over-UDP traffic and potentially broader transmit paths on affected CPUs."
            }
          ]
        }
      ],
      "providerMetadata": {
        "dateUpdated": "2026-08-05T12:33:04.761Z",
        "orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
        "shortName": "Linux"
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          "url": "https://git.kernel.org/stable/c/790093245e35040c2adb15f48970020425aa3f47"
        },
        {
          "url": "https://git.kernel.org/stable/c/2cd7e6971fc2787408ceef17906ea152791448cf"
        }
      ],
      "title": "sctp: disable BH before calling udp_tunnel_xmit_skb()",
      "x_generator": {
        "engine": "bippy-1.2.0"
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  "cveMetadata": {
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    "assignerShortName": "Linux",
    "cveId": "CVE-2026-53070",
    "datePublished": "2026-06-24T16:30:11.816Z",
    "dateReserved": "2026-06-09T07:44:35.382Z",
    "dateUpdated": "2026-08-05T12:33:04.761Z",
    "state": "PUBLISHED"
  },
  "dataType": "CVE_RECORD",
  "dataVersion": "5.2"
}

Sightings

Author	Source	Type	Date	Other

Nomenclature

Seen: The vulnerability was mentioned, discussed, or observed by the user.
Confirmed: The vulnerability has been validated from an analyst's perspective.
Published Proof of Concept: A public proof of concept is available for this vulnerability.
Exploited: The vulnerability was observed as exploited by the user who reported the sighting.
Patched: The vulnerability was observed as successfully patched by the user who reported the sighting.
Not exploited: The vulnerability was not observed as exploited by the user who reported the sighting.
Not confirmed: The user expressed doubt about the validity of the vulnerability.
Not patched: The vulnerability was not observed as successfully patched by the user who reported the sighting.

Detection rules are retrieved from Rulezet.

The MITRE ATT&CK techniques below are AI-generated suggestions, inferred from the description of the vulnerability by the CIRCL/vulnerability-attack-technique-classification-roberta-base model, served locally by ML-Gateway. They have not been verified by an analyst and are provided for guidance only.
The approach is described in our paper Mapping CVEs to MITRE ATT&CK Techniques: A Curated Gold-Set Classifier and the Limits of LLM-Assisted Label Expansion.
Browse all ATT&CK techniques and the vulnerabilities related to each.

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