CVE-2023-52727

Executive Summary

CVE-2023-52727 is a security advisory affecting the Open Networking Foundation SD-RAN ONOS project, specifically the onos-lib-go library version 0.10.25. The vulnerability is an index out-of-range condition in the parseAlignBits function, which can lead to a denial of service (DoS) or potentially exploitable memory corruption. The vulnerability has a CVSS score of 0.0 (likely unassigned or under review) and an EPSS score of 0.0%, indicating low exploitation activity in the wild. No public proof-of-concept (PoC) or patch is currently available.

Supply Chain & Package Security

This vulnerability resides in a Go library (onos-lib-go) used by the SD-RAN ONOS project. As a Go module, it is distributed via standard Go module proxies and version control systems. Organizations using SD-RAN ONOS or any software that depends on onos-lib-go version 0.10.25 are at risk. The lack of a patch means that supply chain security is a significant concern, as downstream consumers cannot easily remediate the issue without forking or applying custom patches.

CVSS Breakdown & Threat Level

The CVSS score is listed as 0.0, which may indicate that the score has not been formally assigned or is under review. Based on the nature of the vulnerability (index out-of-range), a reasonable CVSS vector would be:

• Attack Vector (AV): Network (likely exploitable remotely if the library processes untrusted data)
• Attack Complexity (AC): Low
• Privileges Required (PR): None
• User Interaction (UI): None
• Scope (S): Unchanged
• Confidentiality (C): None (primarily DoS)
• Integrity (I): None
• Availability (A): High

Estimated CVSS Score: 7.5 (High) – based on the potential for remote denial of service.

Threat Level: Medium. While no active exploitation is reported, the vulnerability is in a critical networking component (SD-RAN ONOS) and could be leveraged to disrupt network operations.

Deep Dive & Mechanics

The vulnerability exists in the parseAlignBits function within the onos-lib-go library. This function is responsible for parsing alignment bits from a data stream. An index out-of-range condition occurs when the function attempts to access an array or slice index that is beyond its allocated bounds. This can happen if the input data is malformed or contains unexpected values.

Root Cause: The function likely lacks proper bounds checking before accessing an array or slice. For example, if the function reads a length field from the input and uses it to index into a buffer without verifying that the index is within the valid range, an attacker can craft input that causes an out-of-bounds read or write.

Impact:

• Denial of Service (DoS): The most immediate impact is a panic or crash of the Go application, leading to service disruption.
• Potential Memory Corruption: In some cases, out-of-bounds access can lead to memory corruption, which might be exploitable for arbitrary code execution, though this is less likely in Go due to its memory safety features.

Attack Vector: An attacker could send specially crafted network packets or data to an SD-RAN ONOS component that uses the vulnerable parseAlignBits function. This could be done remotely if the component listens on a network interface.

Vulnerable vs. Patched Code

Since no patch is available, we can only describe the vulnerable code pattern and the expected fix.

Vulnerable Code (Hypothetical):

func parseAlignBits(data []byte) (int, error) {
    // Assume data contains a length field at offset 0
    length := int(data[0])
    // Directly use length to index into data without bounds check
    result := data[length]
    return int(result), nil
}

Patched Code (Expected):

func parseAlignBits(data []byte) (int, error) {
    if len(data) < 1 {
        return 0, errors.New("data too short")
    }
    length := int(data[0])
    if length >= len(data) {
        return 0, errors.New("index out of range")
    }
    result := data[length]
    return int(result), nil
}

The fix involves adding a bounds check before using the index to access the slice.

Exploitation & Lab Setup

Red Team

Objective: Trigger a denial of service in an SD-RAN ONOS component.

Lab Setup:

1. Deploy a vulnerable SD-RAN ONOS instance using onos-lib-go version 0.10.25.
2. Identify a network service that uses the parseAlignBits function (e.g., a gRPC endpoint or REST API).
3. Craft a malicious payload that causes an out-of-bounds access.

Example Payload (Hypothetical):

import socket

# Assume the service listens on TCP port 50051
sock = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
sock.connect(("target_ip", 50051))

# Craft a malformed message that triggers the vulnerability
# The exact format depends on the protocol, but generally includes a large length field
malformed_payload = b"\xff\xff\xff\xff"  # Example: large length value
sock.send(malformed_payload)
sock.close()

Expected Outcome: The target service crashes or becomes unresponsive.

Blue Team

Detection:

• Monitor for application crashes or panics in logs.
• Look for unusual network traffic patterns, especially malformed packets.
• Use the detection rules provided below.

Mitigation:

• If possible, restrict network access to the vulnerable service.
• Implement a Web Application Firewall (WAF) or intrusion prevention system (IPS) to filter malformed requests.
• Monitor for known indicators of compromise (IOCs).

Indicators of Compromise (IOCs)

• Log Entries: Go panic logs containing "index out of range" or "runtime error: index out of range" in the context of parseAlignBits.
• Network Traffic: Malformed packets with unusually large length fields or unexpected data patterns.
• File Hashes: No specific file hashes are available, but any binary or container image using onos-lib-go version 0.10.25 is potentially compromised.

Detection Engineering

YARA Rule

rule CVE_2023_52727_parseAlignBits {
    meta:
        description = "Detects vulnerable parseAlignBits function in onos-lib-go"
        author = "Valters IT"
        date = "2025-04-10"
        reference = "CVE-2023-52727"
    strings:
        $func_name = "parseAlignBits"
        $vuln_pattern = /data\[length\]/ nocase
    condition:
        $func_name and $vuln_pattern
}

Sigma Rule

title: CVE-2023-52727 - Index Out-of-Range in parseAlignBits
id: 8a4b3c2d-1e5f-4a7b-9c8d-0e1f2a3b4c5d
status: experimental
description: Detects potential exploitation attempts of CVE-2023-52727 via application crashes
author: Valters IT
date: 2025-04-10
logsource:
    category: application
    product: go
detection:
    selection:
        EventID: 1000  # Windows Application Error
        Message|contains: "runtime error: index out of range"
    condition: selection
falsepositives:
    - Legitimate application bugs
level: high

Suricata Rule

alert tcp any any -> any any (msg:"CVE-2023-52727 - Potential Index Out-of-Range Exploit"; flow:to_server; content:"|ff ff ff ff|"; depth:4; reference:cve,2023-52727; classtype:attempted-dos; sid:1000001; rev:1;)

Remediation & Mitigation

Immediate Actions:

1. Isolate any systems running onos-lib-go version 0.10.25 from untrusted networks.
2. Monitor logs for signs of exploitation (crashes, panics).
3. Apply network-level filtering to block malformed packets.

Long-term Fix:

• Since no official patch is available, consider forking the onos-lib-go repository and applying the bounds check fix manually.
• Upgrade to a newer version of onos-lib-go if a patched version becomes available.
• Engage with the Open Networking Foundation to request a patch.

Workaround:

• If the vulnerable function is not critical, consider disabling or replacing the component that uses it.

Valters IT
DevSecOps & Cyber Threat Intelligence Expert