CVE-2025-30077

Executive Summary

CVE-2025-30077 is a denial-of-service (DoS) vulnerability in the Open Networking Foundation's SD-RAN ONOS project, specifically within the onos-lib-go library version 0.10.28. The flaw resides in the ASN.1 APER (Aligned Packed Encoding Rules) GetBitString function, where a zero value for numBits triggers an index out-of-range panic. This leads to a crash of the Go application, effectively causing a denial of service. The vulnerability has a CVSS score of 6.2 (Medium) and an EPSS score of 0.0%, indicating low exploitation likelihood at this time. No public proof-of-concept or patch is currently available.

Supply Chain & Package Security

This vulnerability affects the Go package onos-lib-go, which is a core dependency for SD-RAN ONOS components. Organizations using SD-RAN ONOS in their network infrastructure should treat this as a supply chain risk. The vulnerable function is part of the ASN.1 decoding library, which may be used to parse control plane messages. A crafted ASN.1 message with a zero-length bit string can crash the receiver, disrupting SD-RAN operations.

CVSS Breakdown & Threat Level

• CVSS Score: 6.2 (Medium)
• Vector: CVSS:3.1/AV:L/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
• Attack Vector: Local (AV:L) – The attacker must be able to send a crafted ASN.1 message to the vulnerable process.
• Attack Complexity: Low (AC:L) – No special conditions required.
• Privileges Required: None (PR:N) – No authentication needed.
• User Interaction: None (UI:N) – No user action required.
• Scope: Unchanged (S:U) – The vulnerability does not affect other components.
• Confidentiality Impact: None (C:N)
• Integrity Impact: None (I:N)
• Availability Impact: High (A:H) – The process crashes, causing denial of service.

Threat Level: Medium. While the CVSS score is moderate, the potential for disrupting SD-RAN control plane operations makes this a significant concern for network operators.

Deep Dive & Mechanics

The vulnerability is in the GetBitString function within the asn1/aper package of onos-lib-go. This function decodes a bit string from an ASN.1 APER encoded byte stream. The function likely allocates a slice or array based on the numBits parameter. When numBits is zero, the code attempts to access an index that is out of bounds, causing a panic.

Root Cause: Improper validation of the numBits parameter. The function does not check for zero before using it in an indexing operation.

Impact: A remote attacker can send a specially crafted ASN.1 message with a zero-length bit string to a service using this library. The service will crash, leading to a denial of service. In an SD-RAN environment, this could disrupt network slicing, traffic steering, or other control functions.

Vulnerable vs. Patched Code

Vulnerable Code (conceptual):

func GetBitString(data []byte, numBits int) ([]byte, error) {
    // No check for numBits == 0
    result := make([]byte, (numBits + 7) / 8)
    // ... decoding logic that accesses result[0] even if numBits is 0
    return result, nil
}

Patched Code (hypothetical):

func GetBitString(data []byte, numBits int) ([]byte, error) {
    if numBits == 0 {
        return []byte{}, nil // Return empty slice without panic
    }
    result := make([]byte, (numBits + 7) / 8)
    // ... decoding logic
    return result, nil
}

The patch adds a guard clause to handle the zero numBits case gracefully.

Exploitation & Lab Setup

Red Team

Objective: Crash an SD-RAN ONOS component by sending a crafted ASN.1 message.

Lab Setup:

1. Deploy a test environment with SD-RAN ONOS using onos-lib-go v0.10.28.
2. Identify a service that accepts ASN.1 APER encoded messages (e.g., a control plane endpoint).
3. Craft a malicious ASN.1 message with a zero-length bit string.

Example Payload (hex):

// ASN.1 APER encoding for a bit string with numBits=0
// This is a simplified example; actual encoding depends on the specific ASN.1 module.
// The key is to set the length field to 0.
00 00 00 00

Execution:

# Send the crafted message to the target service
echo -ne '\x00\x00\x00\x00' | nc <target_ip> <port>

Expected Outcome: The target service crashes, and the process terminates.

Blue Team

Detection:

• Monitor for process crashes or restarts in SD-RAN ONOS components.
• Look for logs containing "panic" or "index out of range" in the asn1/aper package.
• Use network monitoring to detect malformed ASN.1 messages.

Mitigation:

• Apply the patch as soon as it becomes available.
• Implement input validation at the network edge to reject ASN.1 messages with zero-length bit strings.
• Use a Web Application Firewall (WAF) or intrusion prevention system (IPS) to filter malicious traffic.

Indicators of Compromise (IOCs)

• Log Entry: panic: runtime error: index out of range [0] with length 0 in asn1/aper/GetBitString
• Network Pattern: ASN.1 APER encoded messages with a length field of zero for a bit string.
• Process Behavior: Unexpected termination of onos or related Go processes.

Detection Engineering

YARA Rule

rule CVE_2025_30077_ASN1_Panic {
    meta:
        description = "Detects panic log entries for CVE-2025-30077"
        author = "Valters IT"
        date = "2025-04-10"
        reference = "CVE-2025-30077"
    strings:
        $panic1 = "panic: runtime error: index out of range"
        $panic2 = "asn1/aper/GetBitString"
    condition:
        all of them
}

Sigma Rule

title: CVE-2025-30077 - ASN.1 APER GetBitString Panic
id: 12345678-1234-1234-1234-123456789abc
status: experimental
description: Detects panic log entries indicating exploitation of CVE-2025-30077
author: Valters IT
date: 2025-04-10
logsource:
    product: linux
    service: syslog
detection:
    selection:
        - "panic: runtime error: index out of range"
        - "asn1/aper/GetBitString"
    condition: selection
falsepositives:
    - Legitimate crashes due to other bugs
level: high

Suricata Rule

alert udp any any -> any any (msg:"CVE-2025-30077 - ASN.1 APER Zero-Length Bit String"; content:"|00 00 00 00|"; depth:4; sid:1000001; rev:1;)

Remediation & Mitigation

1. Patch: Apply the official patch from the Open Networking Foundation when released. Monitor the onos-lib-go repository for updates.
2. Workaround: If patching is not immediately possible, implement input validation to reject ASN.1 messages with zero-length bit strings at the application or network level.
3. Monitoring: Enable detailed logging for ASN.1 parsing and monitor for panic events.
4. Network Segmentation: Isolate SD-RAN control plane traffic to trusted networks only.
5. Update Dependencies: Regularly update onos-lib-go and other Go dependencies to the latest versions.

Valters IT
DevSecOps & Cyber Threat Intelligence