How severe is CVE-2025-66577?

CVE-2025-66577 has a CVSS 3.x base score of 5.3, rated medium severity. It is exploitable over network with low attack complexity, requires no privileges and no user interaction. Impact on confidentiality is none, integrity low, and availability none.

Is CVE-2025-66577 being actively exploited?

It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 0% (15th percentile), an estimate of the probability of exploitation in the next 30 days.

What products are affected by CVE-2025-66577?

CVE-2025-66577 affects Yhirose Cpp-httplib. See the affected-products list for the exact vulnerable versions.

How do I fix CVE-2025-66577?

Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround.

Does CVE-2025-66577 have an EU (EUVD) identifier?

Yes. CVE-2025-66577 is tracked in the ENISA EU Vulnerability Database (EUVD) as EUVD-2025-201454.

When was CVE-2025-66577 published?

CVE-2025-66577 was published on 2025-12-05 and last updated on 2026-06-17.

CVE-2025-66577

CVE-2025-66577 is a medium-severity vulnerability in Yhirose Cpp-httplib with a CVSS 3.x base score of 5.3. It is not currently listed as actively exploited by CISA, and its EPSS exploit-prediction score is low. The underlying weakness is classified as CWE-117.

Key facts

Severity: Medium (CVSS 3.x base score 5.3)
EPSS exploit prediction: 0% (15th percentile)
Actively exploited: Not listed in CISA KEV
EU (EUVD) id: EUVD-2025-201454
Weakness: CWE-117
Affected product: Yhirose Cpp-httplib
Published: 2025-12-05
Last modified: 2026-06-17

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.

Frequently asked questions

What is CVE-2025-66577?: 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.
How severe is CVE-2025-66577?: CVE-2025-66577 has a CVSS 3.x base score of 5.3, rated medium severity. It is exploitable over network with low attack complexity, requires no privileges and no user interaction. Impact on confidentiality is none, integrity low, and availability none.
Is CVE-2025-66577 being actively exploited?: It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 0% (15th percentile), an estimate of the probability of exploitation in the next 30 days.
What products are affected by CVE-2025-66577?: CVE-2025-66577 affects Yhirose Cpp-httplib. See the affected-products list for the exact vulnerable versions.
How do I fix CVE-2025-66577?: Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround.
Does CVE-2025-66577 have an EU (EUVD) identifier?: Yes. CVE-2025-66577 is tracked in the ENISA EU Vulnerability Database (EUVD) as EUVD-2025-201454.
When was CVE-2025-66577 published?: CVE-2025-66577 was published on 2025-12-05 and last updated on 2026-06-17.

References

Affected products (1)

cpe:2.3:a:yhirose:cpp-httplib:*:*:*:*:*:*:*:*

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