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Vulnerabilities

Vulnerability · CVE-2025-66570

cpp-httplib is a C++11 single-file header-only cross platform HTTP/HTTPS library.

Published Dec 5, 2025 · catalog updated Dec 5, 2025 · cpp-httplib is a C++11

Last checked Nov 3, 2026. A connected source was read within the last 7 days.

Check if you run it

No confirmed exploitation is on record for CVE-2025-66570. EPSS is 0.34%. Act only if a listed version of cpp-httplib is a C++11 is installed.

Gaps on this record

  • The stored product name is a package slug. The name on this page is taken from the title (cpp-httplib is a C++11).
  • No vendor fix or required action is stored. Compare the linked advisory before you change production.

Same product and reporting

Severity
Critical10.0
Known exploitation
Not in CISA/VulnCheck KEV
EPSS
0.34%
Remediation
Version ranges on file
Affected products
vendor yhirose cpp-httplib < 0.27.0

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 th

Are you affected?

Enter the version you run. The result uses only the ranges stored on this record.

The check returns affected, not affected, or incomplete. It does not guess a version that is missing from the record.

  • vendor yhirose cpp-httplib < 0.27.0< 0.27.0

How to fix CVE-2025-66570

What to do

Three questions, each answered from this record only. Confirm the vendor advisory before you patch.

Should you patch?

No confirmed exploitation is on record for CVE-2025-66570. EPSS is 0.34%. Act only if a listed version of cpp-httplib is a C++11 is installed.

Which versions are affected?

Compare what you have installed with yhirose cpp-httplib < 0.27.0 < 0.27.0. Compare the installed version with the linked vendor advisory before you change production.

What should an analyst verify?

No weakness class is stored. EPSS 0.34%. There is no CISA KEV listing. No Exploit-DB or Metasploit reference is linked. Use the source links for the original advisory.

Code

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

Timeline

Detection, updates, and resolution for this record.

  1. Dec 5, 2025 · EUVD

    Detected

    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 (h

  2. Dec 5, 2025 · EUVD

    Updated

    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 (h

Sources

  • CVE.orgVulnerability recordCVE-2025-66570

    Official CVE identifier

    cve.org
  • FIRST EPSSExploitation probabilityCVE-2025-66570

    30-day exploitation probability 0.34%

    first.org
  • EUVDVulnerability recordEUVD-2025-201455

    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,

    euvd.enisa.europa.eu

References

Freshness

Last verified in this catalog Nov 3, 2026. Significant claims (KEV, EPSS, CVSS, affected ranges) come from the source rows above — open the original publisher for the authoritative advisory.

  • FIRST EPSSNov 3, 2026
  • CVE.orgOct 28, 2026
  • EUVDOct 27, 2026