Medium severity · published Dec 5, 2025
CVE-2025-66577
cpp-httplib Untrusted HTTP Header Handling: X-Forwarded-For/X-Real-IP Trust
5.3
CVSS
0.3%
EPSS
No
On KEV
Description
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 supply X-Forwarded-For or X-Real-IP headers which get accepted unconditionally by get_client_ip() in docker/main.cc, causing access and error logs (nginx_access_logger / nginx_error_logger) to record spoofed client IPs (log poisoning / audit evasion). This vulnerability is fixed in 0.27.0.
CVSS vector
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:N
Attack vector
Network
Complexity
Low
Privileges
None
User interaction
None
Confidentiality
None
Integrity
Low
Availability
None
Scope
Unchanged
Exploitation
Is it being used?
Exploit prediction (EPSS)0.3% · higher than 20% of CVEs
Exploited in the wildNo evidence yet
CISA KEVNot listed
Ransomware campaign useNot known
Affected products
Which versions
CP
cpp-httplib · yhirose
< 0.27.0 · source: vendor, NVD
References
NVD
https://nvd.nist.gov/vuln/detail/CVE-2025-66577
CVE.org
https://www.cve.org/CVERecord?id=CVE-2025-66577
Patch
https://github.com/yhirose/cpp-httplib/commit/ac9ebb0ee333ce8bf13523f487bdfad9518a2aff
Exploit
https://github.com/yhirose/cpp-httplib/security/advisories/GHSA-gfpf-r66f-5mh2
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