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    CVE-2026-21428

    cpp-httplib is a C++11 single-file header-only cross platform HTTP/HTTPS library. Prior to version 0.30.0, the ``write_headers`` function does not check for CR & LF characters in user supplied headers, allowing untrusted header value to escape header lines. This vulnerability allows attackers to add extra headers, modify request body unexpectedly & trigger an SSRF attack. When combined with a server that supports http1.1 pipelining (springboot, python twisted etc), this can be used for server side request forgery (SSRF). Version 0.30.0 fixes this issue.

    Published:Jan 1, 2026
    Last Modified:Apr 18, 2026
    EPS:Jan 1, 2026
    EPSS Score:0.00018
    CVSS Score:7.5

    Affected Products

    Vendor
    Yhirose
    Product
    Cpp-httplib

    Exploits

    https://github.com/yhirose/cpp-httplib/security/advisories/GHSA-wpc6-j37r-jcx7

    Common Attack Pattern Enumeration and Classification (CAPEC)

    CAPEC-15 Command Delimiters
    CAPEC-81 Web Server Logs Tampering

    Related CVEs

    CVE-2026-77358 (CVSS 8.2) — cpp-httplib is a C++ header-only HTTP/HTTPS library. In versions 0.33.0 through 0.50.0, the TLS-enabled WebSoc…
    CVE-2026-77341 (CVSS 5.3) — cpp-httplib is a C++ header-only HTTP/HTTPS library. In version 0.49.0, the chunked-response trailer output pa…
    CVE-2026-54919 (CVSS 7.4) — cpp-httplib is a C++11 single-file header-only cross platform HTTP/HTTPS library. In affected Mbed TLS backend…
    CVE-2026-45372 (CVSS 9.9) — cpp-httplib is a C++11 single-file header-only cross platform HTTP/HTTPS library. Prior to 0.44.0, when cpp-ht…
    CVE-2026-46527 (CVSS 8.7) — cpp-httplib is a C++11 single-file header-only cross platform HTTP/HTTPS library. Prior to 0.44.0, When the se…
    CVE-2026-45352 (CVSS 5.3) — cpp-httplib is a C++11 single-file header-only cross platform HTTP/HTTPS library. Prior to 0.43.4, negative ch…
    CVE-2026-34441 (CVSS 4.8) — cpp-httplib is a C++11 single-file header-only cross platform HTTP/HTTPS library. Prior to version 0.40.0, cpp…
    CVE-2026-33745 (CVSS 7.4) — cpp-httplib is a C++11 single-file header-only cross platform HTTP/HTTPS library. Prior to 0.39.0, the cpp-htt…
    CVE-2026-32627 (CVSS 8.7) — cpp-httplib is a C++11 single-file header-only cross platform HTTP/HTTPS library. Prior to 0.37.2, when a cpp-…
    CVE-2026-31870 (CVSS 7.5) — cpp-httplib is a C++11 single-file header-only cross platform HTTP/HTTPS library. Prior to 0.37.1, when a cpp-…

    Common Vulnerability Scoring System

    Attack Vector
    Network
    Adjacent
    Local
    Physical
    Privileges Required
    None
    Low
    High
    User Interaction
    None
    Required
    Scope
    Unchanged
    Changed
    Confidentiality
    None
    Low
    High
    Integrity
    None
    Low
    High
    Availability
    None
    Low
    High