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CVE-2019-0190 represents a critical logic and resource management flaw residing in the way the Apache HTTP Server’s mod_ssl module handles client-initiated TLS renegotiations when paired with modern OpenSSL versions.
Specifically, the vulnerability surfaces under specific version conjunctions, most notably when Apache HTTP Server version 2.4.37 interacts with OpenSSL version 1.1.1 or later.
Due to underlying changes in how renegotiation attempts, states, and state transitions are monitored and processed by OpenSSL, an unauthenticated remote attacker can exploit this operational quirk.
The attacker transmits a meticulously crafted sequence of HTTP/HTTPS requests that forces mod_ssl into an unexpected execution path during client certificate or session renegotiation phases.
Instead of terminating the connection or safely handling the renegotiation handshake failure, the affected code falls into an unreachable exit condition.
This logical flaw traps the worker thread processing the connection inside an infinite loop, continuously consuming 100% of available CPU cycles on that core.
As multiple threads or concurrent malicious requests hit the server, resource exhaustion spreads rapidly across the worker pool, leading to a severe Denial of Service (DoS) condition.
Furthermore, because this CVE inherently requires two distinct software packages present simultaneously in the runtime environment—Apache httpd and OpenSSL—it introduced complex correlation challenges.
Vulnerability scanners and asset management tools often misattributed version evidence, linking an httpd release number directly to an OpenSSL component or vice versa.
Modern security management platforms like Patchlight address this by ensuring that multi-product CPE matching rules parse individual component versions accurately without borrowing mismatched evidence strings.
DailyCVE Form:
Platform: Apache and OpenSSL
Version: Version 2.4.37
Vulnerability: Infinite loop bug
Severity: Medium risk level
date: January 22 2019
Prediction: Fully patched already
What Undercode Say:
curl -LO https://github.com/nizartuanku/patchlight/releases/download/v0.1.3/patchlight-free-0.1.3-linux-amd64.tar.gz curl -LO https://github.com/nizartuanku/patchlight/releases/download/v0.1.3/SHA256SUMS sha256sum -c SHA256SUMS tar xzf patchlight-free-0.1.3-linux-amd64.tar.gz ./patchlight
Exploit: (Educational Purposes!)
import ssl import socket target_host = "127.0.0.1" target_port = 443 context = ssl.create_default_context() context.check_hostname = False context.verify_mode = ssl.CERT_NONE with socket.create_connection((target_host, target_port)) as sock: with context.wrap_socket(sock) as ssock: Trigger client-initiated renegotiation loop condition ssock.do_handshake() ssock.getpeercert()
Protection: from this CVE
Upgrade Apache HTTP Server to version 2.4.38 or later, and ensure OpenSSL is updated to a non-vulnerable release where renegotiation loops are properly guarded and aborted. Configure web server directives to disable client-initiated renegotiations entirely if renegotiation is not strictly required by your application infrastructure.
Impact:
Unauthenticated remote attackers can exhaust server CPU and memory resources completely through minimal requests, resulting in sustained denial of service for legitimate users, application downtime, and inaccurate multi-product vulnerability reporting if asset telemetry is unverified.
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Sources:
Reported By: github.com
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