VulnerabilityPublished 13 Mar 2026Updated 16 Mar 2026

CVE-2026-32627: yhirose cpp-httplib · Improper Certificate Validation

Affects yhirose cpp-httplibSource CVE Database V5

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Not known to be exploited · CVSS 8.7 High : upgrade to 0.37.2 soon.

Data as of 29 Oct 2026, 19:04 UTC

CVSS 3.1 base score

8.7High

How severe the flaw is on the 0–10 CVSS scale.

EPSS: 0.1% chance of exploitation in 30 days – higher than 8% of CVEsExploit Prediction Scoring System: the likelihood attackers will use this flaw soon.
Patch: Available – fixed in 0.37.2

CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:C/C:H/I:H/A:N

Attack Vector: Network
Attack Complexity: High
Privileges Required: None
User Interaction: None
Scope: Changed
Confidentiality: High
Integrity: High
Availability: None

Bold values are the worst case: easiest to exploit or largest impact.

Attack Vector: Network: The vulnerable component is bound to the network stack and the set of possible attackers extends beyond the other options listed, up to and including the entire Internet. Such a vulnerability is often termed 'remotely exploitable' and can be thought of as an attack being exploitable at the protocol level one or more network hops away (e.g., across one or more routers).
Attack Complexity: High: A successful attack depends on conditions beyond the attacker's control. That is, a successful attack cannot be accomplished at will, but requires the attacker to invest in some measurable amount of effort in preparation or execution against the vulnerable component before a successful attack can be expected. For example, a successful attack may require an attacker to: gather knowledge about the environment in which the vulnerable target/component exists; prepare the target environment to improve exploit reliability; or inject themselves into the logical network path between the target and the resource requested by the victim in order to read and/or modify network communications (e.g., a man in the middle attack).
Privileges Required: None: The attacker is unauthorized prior to attack, and therefore does not require any access to settings or files to carry out an attack.
User Interaction: None: The vulnerable system can be exploited without any interaction from any user.
Scope: Changed: An exploited vulnerability can affect resources beyond the security scope managed by the security authority of the vulnerable component. In this case, the vulnerable component and the impacted component are different and managed by different security authorities.
Confidentiality: High: There is total loss of confidentiality, resulting in all resources within the impacted component being divulged to the attacker. Alternatively, access to only some restricted information is obtained, but the disclosed information presents a direct, serious impact.
Integrity: High: There is a total loss of integrity, or a complete loss of protection. For example, the attacker is able to modify any/all files protected by the impacted component. Alternatively, only some files can be modified, but malicious modification would present a direct, serious consequence to the impacted component.
Availability: None: There is no impact to availability within the impacted component.

Definitions: FIRST CVSS v3.1 specification.

Exploitation evidence

Disclosed: evidence found.
CVE published 13 Mar 2026
Detectable: no evidence on record.
No public nuclei template indexed
Weaponized: no evidence on record.
No public exploit code indexed in Metasploit or Exploit-DB
Exploited in the wildExploited: no evidence on record.
Not in CISA KEV and no source reports exploitation
Observed by OffSeq MirageSeen by Mirage: no evidence on record.
No attack traffic recorded by OffSeq Mirage sensors

A missing step is not evidence of safety. Sources: cve.org (opens in a new tab), the Metasploit, Exploit-DB and nuclei-templates index as of 29 Oct 2026.

Disclosed: The CVE record is public on cve.org. Its publication is t = 0.
Detectable: A public nuclei template can find exposed instances, for defenders and attackers alike.
Weaponized: A Metasploit exploit module or Exploit-DB entry exists (Metasploit scanner modules do not count), or CISA SSVC or the CVSS exploit maturity reports a public proof of concept.
Exploited in the wild: CISA KEV lists it, CISA SSVC rates exploitation active, or a source reports attacks.
Observed by OffSeq Mirage: OffSeq Mirage honeypot sensors recorded attack traffic for this CVE, or found exposed hosts without attack traffic.

Moments are spaced evenly, not to scale; a dashed line marks a gap of six months or more. Deltas count from t = 0. Sources that give only a date (CISA KEV, Exploit-DB, or a time of exactly 00:00Z) read “same day” rather than hours. Metasploit modules carry the flaw’s disclosure date, not their release date, and nuclei templates carry no date, so both appear above but not on the timeline.

What to do

Upgrade cpp-httplib and yhirose/cpp-httplib to 0.37.2.

Affected software

Product	Affected	Fixed in
yhirosecpp-httplib	Affected <0.37.2	Fixed in 0.37.2
GitHubyhirose/cpp-httplib`pkg:github/yhirose/cpp-httplib`Other threats	Affected <0.37.2	Fixed in 0.37.2

Check your own hosts for these packages with threat-finder (opens in a new tab), our free open-source scanner.

AI-suggested

Immediate mitigation requires upgrading cpp-httplib to version 0.37.2 or later where the certificate validation bug is fixed. Until upgrade is possible, organizations should disable automatic redirect following (set_follow_location(false)) when using proxies to prevent the vulnerable code path. Network defenses such as strict proxy controls, TLS interception detection, and network segmentation can reduce exposure to man-in-the-middle attackers. Application developers should audit their use of cpp-httplib to confirm proxy and redirect configurations and ensure TLS verification is enforced. Employing additional TLS validation layers or certificate pinning at the application level can provide defense in depth. Monitoring network traffic for unexpected redirects and anomalous TLS certificates can help detect exploitation attempts. Finally, educating developers and security teams about this specific vulnerability and its conditions is critical to prevent misconfiguration and exploitation.

Description

cpp-httplib is a C++11 single-file header-only cross platform HTTP/HTTPS library. Prior to 0.37.2, when a cpp-httplib client is configured with a proxy and set_follow_location(true), any HTTPS redirect it follows will have TLS certificate and hostname verification silently disabled on the new connection. The client will accept any certificate presented by the redirect target — expired, self-signed, or forged — without raising an error or notifying the application. A network attacker in a position to return a redirect response can fully intercept the follow-up HTTPS connection, including any credentials or session tokens in flight. This vulnerability is fixed in 0.37.2.

Impact

This vulnerability severely compromises the confidentiality and integrity of HTTPS communications made using vulnerable cpp-httplib clients configured with proxies and automatic redirect following. Attackers with network access can perform man-in-the-middle attacks by injecting malicious redirects and presenting invalid TLS certificates that the client will accept without error. This enables interception and potential modification of sensitive data such as authentication credentials, session cookies, and other private information transmitted over HTTPS. Organizations relying on cpp-httplib in proxy environments, especially in internal networks or cloud infrastructures where proxies are common, face risks of credential theft, session hijacking, and data leakage. The vulnerability undermines the fundamental trust model of TLS, potentially exposing critical systems and user data to attackers. Although exploitation requires network-level access, the widespread use of proxies and automatic redirect following in HTTP clients increases the attack surface. The flaw does not affect availability but has high impact on confidentiality and integrity.

CWE-295Improper Certificate Validation (opens in a new tab)
Base weaknessOWASP Top 10 A07:2025: Authentication Failures (opens in a new tab)
The product does not validate, or incorrectly validates, a certificate.
Architecture and Design · Implementation
Certificates should be carefully managed and checked to assure that data are encrypted with the intended owner's public key.
Implementation
If certificate pinning is being used, ensure that all relevant properties of the certificate are fully validated before the certificate is pinned, including the hostname.
OWASP Cheat Sheets
Transport Layer Protection (opens in a new tab)
TLS Cipher String (opens in a new tab)
OWASP Authentication (opens in a new tab)
OWASP ASVS 4.0.3
V9.2.1 (opens in a new tab)
V1.9.2 (opens in a new tab)
V2.8.5 (opens in a new tab)
Attack patterns
Creating a Rogue Certification Authority Certificate (opens in a new tab)
Signature Spoofing by Improper Validation (opens in a new tab)
From MITRE CWE, MITRE CAPEC and OWASP (Top 10, OpenCRE).

References

github.com/yhirose/cpp-httplib/security/advisories/GHSA-c3h8-fqq4-xm4g (opens in a new tab)

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Exploitation evidence

What to do

Affected software

Description

AI analysisMachine-generated, updated 20 Mar 2026, 23:28 UTC

WeaknessesCWE-295

Technical details

References

Community reviews

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