CVE-2026-118373: LibreSSL ocspcheck through 4.4.0 Cleartext Transmission of OCSP Requests via url2host()
LibreSSL ocspcheck through 4.4.0 contains a cleartext transmission vulnerability because url2host() discards the OCSP URL scheme and httpalloc() only selects TLS for port 443. On-path network attackers can read OCSP requests sent to https responder URLs on non-443 ports, exposing certificate serial numbers, issuer hashes, and nonces.
Affected Software
Event History
Frequently Asked Questions
Which deployments are exposed to this issue?
LibreSSL ocspcheck installations through 4.4.0 are exposed when they send OCSP requests to an HTTPS responder URL that uses a port other than 443. Requests to port 443 are selected for TLS by http_alloc().
What does an attacker need to exploit it?
An attacker must be in an on-path network position to observe the OCSP traffic. No authentication or user interaction is required.
What information can be exposed?
The affected requests can be transmitted in cleartext, exposing certificate serial numbers, issuer hashes, and OCSP nonces to the on-path attacker.
What can be done if an update cannot be applied immediately?
Avoid using HTTPS OCSP responder URLs on non-443 ports with ocspcheck. Using port 443 causes http_alloc() to select TLS according to the available data.