Authentication Bypass Affecting cpp-httplib package, versions <0.10.3+ds-1ubuntu0.1~esm1


Severity

Recommended
high

Based on Ubuntu security rating.

Threat Intelligence

EPSS
0.33% (26th percentile)

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  • Snyk IDSNYK-UBUNTU2204-CPPHTTPLIB-14222499
  • published16 Jan 2026
  • disclosed5 Dec 2025

Introduced: 5 Dec 2025

CVE-2025-66570  (opens in a new tab)
CWE-290  (opens in a new tab)
CWE-345  (opens in a new tab)
CWE-807  (opens in a new tab)

How to fix?

Upgrade Ubuntu:22.04 cpp-httplib to version 0.10.3+ds-1ubuntu0.1~esm1 or higher.

NVD Description

Note: Versions mentioned in the description apply only to the upstream cpp-httplib package and not the cpp-httplib package as distributed by Ubuntu. See How to fix? for Ubuntu:22.04 relevant fixed versions and status.

cpp-httplib is a C++11 single-file header-only cross platform HTTP/HTTPS library. Prior to 0.27.0, a vulnerability allows attacker-controlled HTTP headers to influence server-visible metadata, logging, and authorization decisions. An attacker can inject headers named REMOTE_ADDR, REMOTE_PORT, LOCAL_ADDR, LOCAL_PORT that are parsed into the request header multimap via read_headers() in httplib.h (headers.emplace), then the server later appends its own internal metadata using the same header names in Server::process_request without erasing duplicates. Because Request::get_header_value returns the first entry for a header key (id == 0) and the client-supplied headers are parsed before server-inserted headers, downstream code that uses these header names may inadvertently use attacker-controlled values. Affected files/locations: cpp-httplib/httplib.h (read_headers, Server::process_request, Request::get_header_value, get_header_value_u64) and cpp-httplib/docker/main.cc (get_client_ip, nginx_access_logger, nginx_error_logger). Attack surface: attacker-controlled HTTP headers in incoming requests flow into the Request.headers multimap and into logging code that reads forwarded headers, enabling IP spoofing, log poisoning, and authorization bypass via header shadowing. This vulnerability is fixed in 0.27.0.

CVSS Base Scores

version 3.1