cpp-httplib: Malicious `X-Forwarded-For` Under Trusted-Proxy Configuration Triggers Empty `vector::front()`, Leading to Undefined Behavior and Server Crash_CVE-2026-46527

{
    "lastseen": "",
    "description": "cpp-httplib is a C++11 single-file header-only cross platform HTTP/HTTPS library. Prior to 0.44.0, When the server has called Server::set_trusted_proxies() with a non-empty trusted-proxy list, an attacker can send an HTTP request that includes an X-Forwarded-For header whose value parses to no valid IP segments. The code path then executes get_client_ip(), which calls front() on an empty std::vector\u2014undefined behavior in C++. On typical implementations this manifests as abnormal process termination (denial of service). With Sanitizers enabled, you get an explicit runtime diagnostic. This vulnerability is fixed in 0.44.0.",
    "published": "2026-05-29T19:18:26.615Z",
    "modified": "2026-05-29T19:18:26.615Z",
    "type": "cve",
    "title": "cpp-httplib: Malicious `X-Forwarded-For` Under Trusted-Proxy Configuration Triggers Empty `vector::front()`, Leading to Undefined Behavior and Server Crash",
    "source": "GitHub_M",
    "references": "https://github.com/yhirose/cpp-httplib/security/advisories/GHSA-hg3g-vrg8-578g",
    "id": "CVE-2026-46527",
    "bulletinFamily": "",
    "cwe": [
        "CWE-476"
    ],
    "cvelist": null,
    "sourceData": "yhirose cpp-httplib < 0.44.0",
    "sourceHref": "",
    "cvss": {
        "score": 8.7,
        "severity": "HIGH",
        "vector": "CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N",
        "version": "4.0"
    },
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    "href": "",
    "category_name": "CVE",
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    "product": "cpp-httplib",
    "version": "< 0.44.0",
    "vendor": "yhirose",
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}