FKIE_CVE-2026-9545

Vulnerability from fkie_nvd - Published: 2026-07-03 07:16 - Updated: 2026-07-03 07:16
Severity ?
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uses a proper HTTP/3 server for the initial transfers, and when it makes a second transfer to the same site it has been replaced by the attacker's impostor machine - without a valid certificate.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.
References
2499f714-1537-4658-8207-48ae4bb9eae9https://curl.se/docs/CVE-2026-9545.html
2499f714-1537-4658-8207-48ae4bb9eae9https://curl.se/docs/CVE-2026-9545.json
2499f714-1537-4658-8207-48ae4bb9eae9https://hackerone.com/reports/3752888
Impacted products
Vendor Product Version
To clipboard 

{
  "affected": [
    {
      "affectedData": [
        {
          "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"
            }
          ]
        }
      ],
      "source": "2499f714-1537-4658-8207-48ae4bb9eae9"
    }
  ],
  "cveTags": [],
  "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."
    }
  ],
  "id": "CVE-2026-9545",
  "lastModified": "2026-07-03T07:16:25.807",
  "metrics": {},
  "published": "2026-07-03T07:16:25.807",
  "references": [
    {
      "source": "2499f714-1537-4658-8207-48ae4bb9eae9",
      "url": "https://curl.se/docs/CVE-2026-9545.html"
    },
    {
      "source": "2499f714-1537-4658-8207-48ae4bb9eae9",
      "url": "https://curl.se/docs/CVE-2026-9545.json"
    },
    {
      "source": "2499f714-1537-4658-8207-48ae4bb9eae9",
      "url": "https://hackerone.com/reports/3752888"
    }
  ],
  "sourceIdentifier": "2499f714-1537-4658-8207-48ae4bb9eae9",
  "vulnStatus": "Received"
}


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Detection rules are retrieved from Rulezet.