---
id: "CVE-2026-118371"
kind: "vulnerability"
aliases: ["CVE-2026-118371"]
title: "LibreSSL: OCSP request path lets certificate URIs inject HTTP headers"
severity: "medium"
cvss: 6.3
epss: null
exploited: false
status: "open"
category: "infrastructure"
products: []
ecosystems: []
tags: ["infrastructure", "libressl", "openbsd", "self-hosted", "tls"]
not_affected_if: ["no-ocsp-fetch", "openssl-only"]
published_at: "2026-10-28T03:17:13+00:00"
first_seen_at: "2026-10-28T03:31:02+00:00"
updated_at: "2026-10-28T03:32:45+00:00"
sources: [{"source": "nvd", "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-118371", "first_seen_at": "2026-10-28T03:31:02+00:00"}]
---

# LibreSSL: OCSP request path lets certificate URIs inject HTTP headers

LibreSSL through 4.4.0 does not validate the request path that libcrypto's OCSP_sendreq_new() and OCSP_parse_url() write into the OCSP POST request line. A certificate whose Authority Information Access OCSP URI contains carriage return and line feed characters can inject HTTP headers or split requests sent to OCSP responders and proxies.

_Summary, check and fix written by a model from the sources; labelled as such._

## How to check

- Run `openssl version` or the LibreSSL build's version tool to confirm the library version; versions through `4.4.0` are listed as affected
- Check whether your application or service fetches OCSP responses from certificate AIA URIs using LibreSSL libcrypto (unknown whether this is exposed in default configurations)

## Fix

- Upgrade LibreSSL to a release later than `4.4.0` (fixed version unknown from the sources)
- Until patched, avoid processing untrusted certificates that trigger OCSP fetches through LibreSSL

## Timeline

- 2026-10-28T03:31:02+00:00 nvd https://nvd.nist.gov/vuln/detail/CVE-2026-118371

## From the sources

LibreSSL through 4.4.0 contains a CRLF injection vulnerability in the libcrypto OCSP_sendreq_new() and OCSP_parse_url() functions, which write unvalidated request paths into the OCSP POST request line. Attackers can embed carriage return and line feed characters in a certificate's Authority Information Access OCSP URI to inject HTTP headers or split requests sent to responders and proxies.

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_Free to read at a human pace. An API with keys and an MCP server are in preparation; early access: hello@infrastack.ai_