Vulnerability-Lookup

GHSA-6V72-WFCJ-JV53

Vulnerability from github – Published: 2026-07-03 09:31 – Updated: 2026-07-06 18:30

Details

When libcurl returns to the hostname the second time with a cached SSL session (CURLOPT_SSL_SESSIONID_CACHE is not disabled) and early data enabled (the CURLSSLOPT_EARLYDATA bit is set in CURLOPT_SSL_OPTIONS), libcurl might send off the second request's bytes on that new connection before enforcing the certificate verification failure. Potentially leaking sensitive information.

Severity

7.5 (High)


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

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{
  "affected": [],
  "aliases": [
    "CVE-2026-9545"
  ],
  "database_specific": {
    "cwe_ids": [
      "CWE-200"
    ],
    "github_reviewed": false,
    "github_reviewed_at": null,
    "nvd_published_at": "2026-07-03T07:16:25Z",
    "severity": "HIGH"
  },
  "details": "In this scenario, libcurl first uses a proper HTTP/3 server for the initial\ntransfers, and when it makes a second transfer to the same site it has been\nreplaced by the attacker\u0027s impostor machine - without a valid certificate.\n\nWhen libcurl returns to the hostname the second time with a cached SSL session\n(`CURLOPT_SSL_SESSIONID_CACHE` is not disabled) and early data enabled (the\n`CURLSSLOPT_EARLYDATA` bit is set in `CURLOPT_SSL_OPTIONS`), libcurl might\nsend off the second request\u0027s bytes on that new connection *before* enforcing\nthe certificate verification failure. Potentially leaking sensitive\ninformation.",
  "id": "GHSA-6v72-wfcj-jv53",
  "modified": "2026-07-06T18:30:50Z",
  "published": "2026-07-03T09:31:27Z",
  "references": [
    {
      "type": "ADVISORY",
      "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-9545"
    },
    {
      "type": "WEB",
      "url": "https://hackerone.com/reports/3752888"
    },
    {
      "type": "WEB",
      "url": "https://curl.se/docs/CVE-2026-9545.html"
    },
    {
      "type": "WEB",
      "url": "https://curl.se/docs/CVE-2026-9545.json"
    }
  ],
  "schema_version": "1.4.0",
  "severity": [
    {
      "score": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N",
      "type": "CVSS_V3"
    }
  ]
}

CVE-2026-9545 (GCVE-0-2026-9545)

Vulnerability from cvelistv5 – Published: 2026-07-03 06:17 – Updated: 2026-09-15 06:03

Title

exposing HTTP/3 early data

Summary

In this scenario, libcurl first uses a proper HTTP/3 server for the initial transfers, and when it makes a second transfer to the same site it has been replaced by the attacker's impostor machine - without a valid certificate. When libcurl returns to the hostname the second time with a cached SSL session (`CURLOPT_SSL_SESSIONID_CACHE` is not disabled) and early data enabled (the `CURLSSLOPT_EARLYDATA` bit is set in `CURLOPT_SSL_OPTIONS`), libcurl might send off the second request's bytes on that new connection *before* enforcing the certificate verification failure. Potentially leaking sensitive information.

Severity

7.5 (High)


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

SSVC

Exploitation: poc Automatable: yes Technical Impact: partial

CISA Coordinator · CISA-ADP (v2.0.3)

Decision recorded 2026-07-06 16:52 UTC

CWE

CWE-200 - Exposure of Sensitive Information to an Unauthorized Actor

Assigner

curl redhat root

References

3 references

URL	Tags
https://curl.se/docs/CVE-2026-9545.json
https://curl.se/docs/CVE-2026-9545.html
https://hackerone.com/reports/3752888

Impacted products

3 products

Vendor	Product	Version
curl	curl	Affected: 8.11.0 , < 8.14.2 (semver) Affected: 8.15.0 , < 8.16.1 (semver) Affected: 8.17.0 , < 8.20.1 (semver)
curl	curl	Affected: 962097b8dd44ed5b9e7984bc1cdffdbdd566857f , < 7b9613fa9b1a5e04301a3920eef58e8138dad05e (git)
curl	curl	Affected: 8.20.0 Affected: 8.19.0 Affected: 8.18.0 Affected: 8.17.0 Affected: 8.16.0 Affected: 8.15.0 Affected: 8.14.1 Affected: 8.14.0 Affected: 8.13.0 Affected: 8.12.1 Affected: 8.12.0 Affected: 8.11.1 Affected: 8.11.0

Credits

Eunsoo Kim (Autonomous Code Security team at Microsoft) Stefan Eissing

Show details on NVD website

JSON

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{
  "containers": {
    "adp": [
      {
        "metrics": [
          {
            "cvssV3_1": {
              "attackComplexity": "LOW",
              "attackVector": "NETWORK",
              "availabilityImpact": "NONE",
              "baseScore": 7.5,
              "baseSeverity": "HIGH",
              "confidentialityImpact": "HIGH",
              "integrityImpact": "NONE",
              "privilegesRequired": "NONE",
              "scope": "UNCHANGED",
              "userInteraction": "NONE",
              "vectorString": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N",
              "version": "3.1"
            }
          },
          {
            "other": {
              "content": {
                "id": "CVE-2026-9545",
                "options": [
                  {
                    "Exploitation": "poc"
                  },
                  {
                    "Automatable": "yes"
                  },
                  {
                    "Technical Impact": "partial"
                  }
                ],
                "role": "CISA Coordinator",
                "timestamp": "2026-07-06T16:52:42.898546Z",
                "version": "2.0.3"
              },
              "type": "ssvc"
            }
          }
        ],
        "providerMetadata": {
          "dateUpdated": "2026-07-06T16:53:23.396Z",
          "orgId": "134c704f-9b21-4f2e-91b3-4a467353bcc0",
          "shortName": "CISA-ADP"
        },
        "references": [
          {
            "tags": [
              "exploit"
            ],
            "url": "https://hackerone.com/reports/3752888"
          }
        ],
        "title": "CISA ADP Vulnrichment"
      }
    ],
    "cna": {
      "affected": [
        {
          "defaultStatus": "unaffected",
          "product": "curl",
          "vendor": "curl",
          "versions": [
            {
              "lessThan": "8.14.2",
              "status": "affected",
              "version": "8.11.0",
              "versionType": "semver"
            },
            {
              "lessThan": "8.16.1",
              "status": "affected",
              "version": "8.15.0",
              "versionType": "semver"
            },
            {
              "lessThan": "8.20.1",
              "status": "affected",
              "version": "8.17.0",
              "versionType": "semver"
            }
          ]
        },
        {
          "defaultStatus": "unaffected",
          "product": "curl",
          "repo": "https://github.com/curl/curl.git",
          "vendor": "curl",
          "versions": [
            {
              "lessThan": "7b9613fa9b1a5e04301a3920eef58e8138dad05e",
              "status": "affected",
              "version": "962097b8dd44ed5b9e7984bc1cdffdbdd566857f",
              "versionType": "git"
            }
          ]
        },
        {
          "defaultStatus": "unaffected",
          "product": "curl",
          "vendor": "curl",
          "versions": [
            {
              "status": "affected",
              "version": "8.20.0"
            },
            {
              "status": "affected",
              "version": "8.19.0"
            },
            {
              "status": "affected",
              "version": "8.18.0"
            },
            {
              "status": "affected",
              "version": "8.17.0"
            },
            {
              "status": "affected",
              "version": "8.16.0"
            },
            {
              "status": "affected",
              "version": "8.15.0"
            },
            {
              "status": "affected",
              "version": "8.14.1"
            },
            {
              "status": "affected",
              "version": "8.14.0"
            },
            {
              "status": "affected",
              "version": "8.13.0"
            },
            {
              "status": "affected",
              "version": "8.12.1"
            },
            {
              "status": "affected",
              "version": "8.12.0"
            },
            {
              "status": "affected",
              "version": "8.11.1"
            },
            {
              "status": "affected",
              "version": "8.11.0"
            }
          ]
        }
      ],
      "credits": [
        {
          "lang": "en",
          "type": "finder",
          "value": "Eunsoo Kim (Autonomous Code Security team at Microsoft)"
        },
        {
          "lang": "en",
          "type": "remediation developer",
          "value": "Stefan Eissing"
        }
      ],
      "descriptions": [
        {
          "lang": "en",
          "value": "In this scenario, libcurl first uses a proper HTTP/3 server for the initial\ntransfers, and when it makes a second transfer to the same site it has been\nreplaced by the attacker\u0027s impostor machine - without a valid certificate.\n\nWhen libcurl returns to the hostname the second time with a cached SSL session\n(`CURLOPT_SSL_SESSIONID_CACHE` is not disabled) and early data enabled (the\n`CURLSSLOPT_EARLYDATA` bit is set in `CURLOPT_SSL_OPTIONS`), libcurl might\nsend off the second request\u0027s bytes on that new connection *before* enforcing\nthe certificate verification failure. Potentially leaking sensitive\ninformation."
        }
      ],
      "problemTypes": [
        {
          "descriptions": [
            {
              "cweId": "CWE-200",
              "description": "Exposure of Sensitive Information to an Unauthorized Actor",
              "lang": "en",
              "type": "CWE"
            }
          ]
        }
      ],
      "providerMetadata": {
        "dateUpdated": "2026-09-15T06:03:31.804Z",
        "orgId": "2499f714-1537-4658-8207-48ae4bb9eae9",
        "shortName": "curl"
      },
      "references": [
        {
          "url": "https://curl.se/docs/CVE-2026-9545.json"
        },
        {
          "url": "https://curl.se/docs/CVE-2026-9545.html"
        },
        {
          "url": "https://hackerone.com/reports/3752888"
        }
      ],
      "title": "exposing HTTP/3 early data",
      "x_generator": {
        "engine": "cvelib 1.8.0"
      },
      "x_osv": {
        "affected": [
          {
            "ranges": [
              {
                "events": [
                  {
                    "introduced": "8.11.0"
                  },
                  {
                    "fixed": "8.14.2"
                  },
                  {
                    "introduced": "8.15.0"
                  },
                  {
                    "fixed": "8.16.1"
                  },
                  {
                    "introduced": "8.17.0"
                  },
                  {
                    "fixed": "8.20.1"
                  }
                ],
                "type": "SEMVER"
              },
              {
                "events": [
                  {
                    "introduced": "962097b8dd44ed5b9e7984bc1cdffdbdd566857f"
                  },
                  {
                    "fixed": "7b9613fa9b1a5e04301a3920eef58e8138dad05e"
                  }
                ],
                "repo": "https://github.com/curl/curl.git",
                "type": "GIT"
              }
            ],
            "versions": [
              "8.20.0",
              "8.19.0",
              "8.18.0",
              "8.17.0",
              "8.16.0",
              "8.15.0",
              "8.14.1",
              "8.14.0",
              "8.13.0",
              "8.12.1",
              "8.12.0",
              "8.11.1",
              "8.11.0"
            ]
          }
        ],
        "aliases": [
          "CVE-2026-9545"
        ],
        "credits": [
          {
            "name": "Eunsoo Kim (Autonomous Code Security team at Microsoft)",
            "type": "finder"
          },
          {
            "name": "Stefan Eissing",
            "type": "remediation developer"
          }
        ],
        "database_specific": {
          "CWE": {
            "desc": "Exposure of Sensitive Information to an Unauthorized Actor",
            "id": "CWE-200"
          },
          "URL": "https://curl.se/docs/CVE-2026-9545.json",
          "affects": "both",
          "issue": "https://hackerone.com/reports/3752888",
          "last_affected": "8.20.0",
          "package": "curl",
          "severity": "Low",
          "www": "https://curl.se/docs/CVE-2026-9545.html"
        },
        "details": "In this scenario, libcurl first uses a proper HTTP/3 server for the initial\ntransfers, and when it makes a second transfer to the same site it has been\nreplaced by the attacker\u0027s impostor machine - without a valid certificate.\n\nWhen libcurl returns to the hostname the second time with a cached SSL session\n(`CURLOPT_SSL_SESSIONID_CACHE` is not disabled) and early data enabled (the\n`CURLSSLOPT_EARLYDATA` bit is set in `CURLOPT_SSL_OPTIONS`), libcurl might\nsend off the second request\u0027s bytes on that new connection *before* enforcing\nthe certificate verification failure. Potentially leaking sensitive\ninformation.",
        "id": "CURL-CVE-2026-9545",
        "modified": "2026-09-07T10:34:51.00Z",
        "published": "2026-06-24T08:00:00.00Z",
        "schema_version": "1.5.0",
        "summary": "exposing HTTP/3 early data"
      }
    }
  },
  "cveMetadata": {
    "assignerOrgId": "2499f714-1537-4658-8207-48ae4bb9eae9",
    "assignerShortName": "curl",
    "cveId": "CVE-2026-9545",
    "datePublished": "2026-07-03T06:17:55.931Z",
    "dateReserved": "2026-05-26T06:45:08.680Z",
    "dateUpdated": "2026-09-15T06:03:31.804Z",
    "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.

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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GHSA-6V72-WFCJ-JV53

CVE-2026-9545 (GCVE-0-2026-9545)

Tags

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