cpp-httplib's default exception handler leaks e.what() to clients via EXCEPTION_WHAT response header

{
  "dataType": "CVE_RECORD",
  "dataVersion": "5.2",
  "cveMetadata": {
    "cveId": "CVE-2026-28434",
    "assignerOrgId": "a0819718-46f1-4df5-94e2-005712e83aaa",
    "assignerShortName": "GitHub_M",
    "dateUpdated": "2026-03-04T20:55:40.320Z",
    "dateReserved": "2026-02-27T15:54:05.138Z",
    "datePublished": "2026-03-04T19:34:30.486Z",
    "state": "PUBLISHED"
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        "shortName": "GitHub_M",
        "dateUpdated": "2026-03-04T19:34:30.486Z"
      },
      "title": "cpp-httplib's default exception handler leaks e.what() to clients via EXCEPTION_WHAT response header",
      "descriptions": [
        {
          "lang": "en",
          "value": "cpp-httplib is a C++11 single-file header-only cross platform HTTP/HTTPS library. Prior to 0.35.0, when a request handler throws a C++ exception and the application has not registered a custom exception handler via set_exception_handler(), the library catches the exception and writes its message directly into the HTTP response as a header named EXCEPTION_WHAT. This header is sent to whoever made the request, with no authentication check and no special configuration required to trigger it. The behavior is on by default. A developer who does not know to opt in to set_exception_handler() will ship a server that leaks internal exception messages to any client. This vulnerability is fixed in 0.35.0."
        }
      ],
      "affected": [
        {
          "vendor": "yhirose",
          "product": "cpp-httplib",
          "versions": [
            {
              "version": "< 0.35.0",
              "status": "affected"
            }
          ]
        }
      ],
      "problemTypes": [
        {
          "descriptions": [
            {
              "lang": "en",
              "description": "CWE-200: Exposure of Sensitive Information to an Unauthorized Actor",
              "cweId": "CWE-200",
              "type": "CWE"
            }
          ]
        }
      ],
      "references": [
        {
          "url": "https://github.com/yhirose/cpp-httplib/security/advisories/GHSA-8mpw-r4gc-xm7q",
          "name": "https://github.com/yhirose/cpp-httplib/security/advisories/GHSA-8mpw-r4gc-xm7q",
          "tags": [
            "x_refsource_CONFIRM"
          ]
        },
        {
          "url": "https://github.com/yhirose/cpp-httplib/commit/defd907c7469c5c8281247b73bbd07be24c31164",
          "name": "https://github.com/yhirose/cpp-httplib/commit/defd907c7469c5c8281247b73bbd07be24c31164",
          "tags": [
            "x_refsource_MISC"
          ]
        }
      ],
      "metrics": [
        {
          "cvssV3_1": {
            "version": "3.1",
            "vectorString": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:N/A:N",
            "attackVector": "NETWORK",
            "attackComplexity": "LOW",
            "privilegesRequired": "NONE",
            "userInteraction": "NONE",
            "scope": "UNCHANGED",
            "confidentialityImpact": "LOW",
            "integrityImpact": "NONE",
            "availabilityImpact": "NONE",
            "baseScore": 5.3,
            "baseSeverity": "MEDIUM"
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          "dateUpdated": "2026-03-04T20:55:40.320Z"
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        "title": "CISA ADP Vulnrichment",
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