Vulnerability-Lookup

GHSA-6V72-WFCJ-JV53

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

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.

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{
  "affected": [],
  "aliases": [
    "CVE-2026-9545"
  ],
  "database_specific": {
    "cwe_ids": [],
    "github_reviewed": false,
    "github_reviewed_at": null,
    "nvd_published_at": "2026-07-03T07:16:25Z",
    "severity": null
  },
  "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": "2026-07-03T09:31:27Z",
  "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": []
}

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

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

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uses a proper HTTP/3 server for the initial transfers, and when it makes a second transfer to the same site it has been replaced by the attacker's impostor machine - without a valid certificate.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 ?

No CVSS data available.

CWE

CWE-200 Exposure of Sensitive Information to an Unauthorized Actor

Assigner

curl

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

	Vendor	Product	Version
	curl	curl	Affected: 8.20.0 , ≤ 8.20.0 (semver) Affected: 8.19.0 , ≤ 8.19.0 (semver) Affected: 8.18.0 , ≤ 8.18.0 (semver) Affected: 8.17.0 , ≤ 8.17.0 (semver) Affected: 8.16.0 , ≤ 8.16.0 (semver) Affected: 8.15.0 , ≤ 8.15.0 (semver) Affected: 8.14.1 , ≤ 8.14.1 (semver) Affected: 8.14.0 , ≤ 8.14.0 (semver) Affected: 8.13.0 , ≤ 8.13.0 (semver) Affected: 8.12.1 , ≤ 8.12.1 (semver) Affected: 8.12.0 , ≤ 8.12.0 (semver) Affected: 8.11.1 , ≤ 8.11.1 (semver) Affected: 8.11.0 , ≤ 8.11.0 (semver)

Credits

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

Show details on NVD website

JSON

To clipboard

{
  "containers": {
    "cna": {
      "affected": [
        {
          "defaultStatus": "unaffected",
          "product": "curl",
          "vendor": "curl",
          "versions": [
            {
              "lessThanOrEqual": "8.20.0",
              "status": "affected",
              "version": "8.20.0",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "8.19.0",
              "status": "affected",
              "version": "8.19.0",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "8.18.0",
              "status": "affected",
              "version": "8.18.0",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "8.17.0",
              "status": "affected",
              "version": "8.17.0",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "8.16.0",
              "status": "affected",
              "version": "8.16.0",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "8.15.0",
              "status": "affected",
              "version": "8.15.0",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "8.14.1",
              "status": "affected",
              "version": "8.14.1",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "8.14.0",
              "status": "affected",
              "version": "8.14.0",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "8.13.0",
              "status": "affected",
              "version": "8.13.0",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "8.12.1",
              "status": "affected",
              "version": "8.12.1",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "8.12.0",
              "status": "affected",
              "version": "8.12.0",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "8.11.1",
              "status": "affected",
              "version": "8.11.1",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "8.11.0",
              "status": "affected",
              "version": "8.11.0",
              "versionType": "semver"
            }
          ]
        }
      ],
      "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": [
            {
              "description": "CWE-200 Exposure of Sensitive Information to an Unauthorized Actor",
              "lang": "en"
            }
          ]
        }
      ],
      "providerMetadata": {
        "dateUpdated": "2026-07-03T06:17:55.931Z",
        "orgId": "2499f714-1537-4658-8207-48ae4bb9eae9",
        "shortName": "curl"
      },
      "references": [
        {
          "name": "json",
          "url": "https://curl.se/docs/CVE-2026-9545.json"
        },
        {
          "name": "www",
          "url": "https://curl.se/docs/CVE-2026-9545.html"
        },
        {
          "name": "issue",
          "url": "https://hackerone.com/reports/3752888"
        }
      ],
      "title": "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": "2026-07-03T06:17:55.931Z",
    "state": "PUBLISHED"
  },
  "dataType": "CVE_RECORD",
  "dataVersion": "5.2"
}

Sightings

Author	Source	Type	Date

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.

Action not permitted

GHSA-6V72-WFCJ-JV53

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

Tags

Sightings

Nomenclature