Vulnerability-Lookup

GHSA-Q27J-H4QM-X5F7

Vulnerability from github – Published: 2026-09-01 21:31 – Updated: 2026-09-01 21:31

Details

The BLOCKED access control list items that are evaluated to deny access on the the proxy protocol port can be bypassed completely when connecting over TCP or TLS and sending the query twice on connection that is kept open.

Severity

8.2 (High)


                  
                    CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:H/VI:N/VA:N/SC:N/SI:N/SA:N

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{
  "affected": [],
  "aliases": [
    "CVE-2026-19538"
  ],
  "database_specific": {
    "cwe_ids": [
      "CWE-290"
    ],
    "github_reviewed": false,
    "github_reviewed_at": null,
    "nvd_published_at": "2026-08-26T09:16:46Z",
    "severity": "HIGH"
  },
  "details": "The BLOCKED access control list items that are evaluated to deny access on the the proxy protocol port can be bypassed completely when connecting over TCP or TLS and sending the query twice on connection that is kept open.",
  "id": "GHSA-q27j-h4qm-x5f7",
  "modified": "2026-09-01T21:31:25Z",
  "published": "2026-09-01T21:31:25Z",
  "references": [
    {
      "type": "ADVISORY",
      "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-19538"
    },
    {
      "type": "WEB",
      "url": "https://www.nlnetlabs.nl/downloads/nsd/CVE-2026-19538.txt"
    }
  ],
  "schema_version": "1.4.0",
  "severity": [
    {
      "score": "CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:H/VI:N/VA:N/SC:N/SI:N/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X",
      "type": "CVSS_V4"
    }
  ]
}

CVE-2026-19538 (GCVE-0-2026-19538)

Vulnerability from cvelistv5 – Published: 2026-08-26 08:47 – Updated: 2026-08-26 14:00

Title

Bypass of BLOCKED ACL items on proxy protocol port over TCP or TLS

Summary

Severity

8.2 (High)


                        
                          CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:H/VI:N/VA:N/SC:N/SI:N/SA:N

SSVC

Exploitation: none Automatable: no Technical Impact: partial

CISA Coordinator · CISA-ADP (v2.0.3)

Decision recorded 2026-08-26 13:51 UTC

CWE

CWE-290 - Authentication Bypass by Spoofing
CWE-672 - Operation on a Resource after Expiration or Release

Assigner

NLnet Labs

References

1 reference

URL	Tags
https://www.nlnetlabs.nl/downloads/nsd/CVE-2026-1…	vendor-advisory

Impacted products

1 product

Vendor	Product	Version
NLnet Labs	NSD	Affected: 4.8.0 , < 4.15.1 (semver)

Date Public

2026-08-26 12:00

Credits

Qifan Zhang from Palo Alto Networks

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JSON

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{
  "containers": {
    "adp": [
      {
        "metrics": [
          {
            "other": {
              "content": {
                "id": "CVE-2026-19538",
                "options": [
                  {
                    "Exploitation": "none"
                  },
                  {
                    "Automatable": "no"
                  },
                  {
                    "Technical Impact": "partial"
                  }
                ],
                "role": "CISA Coordinator",
                "timestamp": "2026-08-26T13:51:21.490331Z",
                "version": "2.0.3"
              },
              "type": "ssvc"
            }
          }
        ],
        "providerMetadata": {
          "dateUpdated": "2026-08-26T14:00:12.918Z",
          "orgId": "134c704f-9b21-4f2e-91b3-4a467353bcc0",
          "shortName": "CISA-ADP"
        },
        "title": "CISA ADP Vulnrichment"
      }
    ],
    "cna": {
      "affected": [
        {
          "defaultStatus": "unaffected",
          "product": "NSD",
          "vendor": "NLnet Labs",
          "versions": [
            {
              "lessThan": "4.15.1",
              "status": "affected",
              "version": "4.8.0",
              "versionType": "semver"
            }
          ]
        }
      ],
      "credits": [
        {
          "lang": "en",
          "type": "finder",
          "value": "Qifan Zhang from Palo Alto Networks"
        }
      ],
      "datePublic": "2026-08-26T12:00:00.000Z",
      "descriptions": [
        {
          "lang": "en",
          "value": "The BLOCKED access control list items that are evaluated to deny access on the the proxy protocol port can be bypassed completely when connecting over TCP or TLS and sending the query twice on connection that is kept open."
        }
      ],
      "metrics": [
        {
          "cvssV4_0": {
            "baseScore": 8.2,
            "baseSeverity": "HIGH",
            "vectorString": "CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:H/VI:N/VA:N/SC:N/SI:N/SA:N",
            "version": "4.0"
          },
          "format": "CVSS",
          "scenarios": [
            {
              "lang": "en",
              "value": "Explicitly denied access to the proxy protocol port is bypassed on TCP or TLS"
            }
          ]
        }
      ],
      "problemTypes": [
        {
          "descriptions": [
            {
              "cweId": "CWE-290",
              "description": "CWE-290 Authentication Bypass by Spoofing",
              "lang": "en",
              "type": "CWE"
            },
            {
              "cweId": "CWE-672",
              "description": "CWE-672 Operation on a Resource after Expiration or Release",
              "lang": "en",
              "type": "CWE"
            }
          ]
        }
      ],
      "providerMetadata": {
        "dateUpdated": "2026-08-26T08:47:08.992Z",
        "orgId": "206fc3a0-e175-490b-9eaa-a5738056c9f6",
        "shortName": "NLnet Labs"
      },
      "references": [
        {
          "tags": [
            "vendor-advisory"
          ],
          "url": "https://www.nlnetlabs.nl/downloads/nsd/CVE-2026-19538.txt"
        }
      ],
      "solutions": [
        {
          "lang": "en",
          "value": "This issue is fixed in 4.15.1 and all later versions."
        }
      ],
      "timeline": [
        {
          "lang": "en",
          "time": "2026-07-15T18:04:25.000Z",
          "value": "Issue reported by Qifan Zhang"
        },
        {
          "lang": "en",
          "time": "2026-08-10T07:56:32.000Z",
          "value": "NLnet Labs shares patch"
        },
        {
          "lang": "en",
          "time": "2026-08-15T00:00:00.000Z",
          "value": "Qifan Zhang verifies patch"
        },
        {
          "lang": "en",
          "time": "2026-08-26T12:00:00.000Z",
          "value": "Fix released with version 4.15.1"
        }
      ],
      "title": "Bypass of BLOCKED ACL items on proxy protocol port over TCP or TLS",
      "x_generator": {
        "engine": "cvelib 1.8.0"
      }
    }
  },
  "cveMetadata": {
    "assignerOrgId": "206fc3a0-e175-490b-9eaa-a5738056c9f6",
    "assignerShortName": "NLnet Labs",
    "cveId": "CVE-2026-19538",
    "datePublished": "2026-08-26T08:47:08.992Z",
    "dateReserved": "2026-08-11T10:27:22.294Z",
    "dateUpdated": "2026-08-26T14:00:12.918Z",
    "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.

Action not permitted

GHSA-Q27J-H4QM-X5F7

CVE-2026-19538 (GCVE-0-2026-19538)

Tags

Sightings

Nomenclature