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Findings

CVE-2026-103930

cpp-httplib is a C++ header-only HTTP/HTTPS library.

Published Oct 14, 2026 · updated Oct 15, 2026

cpp-httplib is a C++ header-only HTTP/HTTPS library. From 0.29.0 until 0.51.0, Client::open_stream in httplib.h accepts a caller-controlled path that reaches detail::write_request_line() without the detail::encode_path() protection used by the ordinary buffered request path. Raw carriage-return and line-feed bytes in the path can therefore split the outbound HTTP/1.1 request line and inject attacker-shaped request metadata. Exploitation requires an embedding application to pass remote user input into the open_stream path and a backend or intermediary that interprets the injected bytes; the established impact is modification of backend-visible request data, not direct confidentiality or availability impact. This issue is fixed in version 0.51.0.

Code

The project this record applies to. Exploit listings stay in References.

Timeline

Detection, updates, and resolution for this record.

  1. Oct 14, 2026 · NIST NVD

    Detected

    cpp-httplib is a C++ header-only HTTP/HTTPS library. From 0.29.0 until 0.51.0, Client::open_stream in httplib.h accepts a caller-controlled path that reaches detail::write_request_line() without the detail::encode_path() protection used by the ordinary buffered request path. Raw carriage-return and line-feed bytes in the path can therefore split the outbound HTTP/1.1 request line and inject attack

  2. Oct 15, 2026 · NIST NVD

    Updated

    cpp-httplib is a C++ header-only HTTP/HTTPS library. From 0.29.0 until 0.51.0, Client::open_stream in httplib.h accepts a caller-controlled path that reaches detail::write_request_line() without the detail::encode_path() protection used by the ordinary buffered request path. Raw carriage-return and line-feed bytes in the path can therefore split the outbound HTTP/1.1 request line and inject attack

Sources

  • CVE.orgVulnerability recordCVE-2026-103930

    Official CVE identifier

    cve.org
  • FIRST EPSSExploitation probabilityCVE-2026-103930

    30-day exploitation probability 0.4%

    first.org
  • NIST NVDVulnerability recordCVE-2026-103930

    cpp-httplib is a C++ header-only HTTP/HTTPS library. From 0.29.0 until 0.51.0, Client::open_stream in httplib.h accepts a caller-controlled path that reaches detail::write_request_line() without the detail::encode_path() protection used by the ordinary buffered request path. Raw

    nvd.nist.gov

References