CVE-2025-52893

Executive Summary

CVE-2025-52893 is a medium-severity information disclosure vulnerability affecting OpenBao, a secrets management solution. The flaw allows sensitive data to be leaked in application logs when the system processes malformed or improperly formatted requests. This issue is distinct from the previously disclosed HCSEC-2025-09 / CVE-2025-4166. The vulnerability has been addressed in OpenBao version 2.3.0. There are no known workarounds, and the only mitigation is to ensure all clients send properly formatted requests and to upgrade to the patched version. The EPSS score is 0.0%, indicating a very low probability of exploitation in the wild at this time.

Supply Chain & Package Security

OpenBao is a Go-based project. The vulnerability does not directly affect the supply chain of packages (NPM, PyPI, Ruby, etc.), but it does impact the security posture of any organization using OpenBao to manage secrets. A compromised log file could expose sensitive credentials, API keys, or certificates, leading to downstream supply chain risks if those secrets are used to access other systems or package registries.

CVSS Breakdown & Threat Level

• CVSS Score: 4.5 (Medium)
• Attack Vector (AV): Local (AV:L) – The attacker must have local access to the system or logs.
• Attack Complexity (AC): Low (AC:L) – No special conditions are required.
• Privileges Required (PR): Low (PR:L) – The attacker needs low-level privileges to read logs.
• User Interaction (UI): None (UI:N) – No user action is required.
• Scope (S): Unchanged (S:U) – The impact is confined to the vulnerable component.
• Confidentiality (C): Low (C:L) – Limited information disclosure.
• Integrity (I): None (I:N) – No integrity impact.
• Availability (A): None (A:N) – No availability impact.

Threat Level: Medium. The vulnerability requires local access to logs, but the potential exposure of secrets makes it a significant concern for organizations that rely on OpenBao for sensitive data management.

Deep Dive & Mechanics

The vulnerability resides in OpenBao's request processing logic. When the system receives malformed or improperly structured data, it may inadvertently include sensitive information (such as secret values, tokens, or keys) in the log output. This occurs because the logging mechanism does not properly sanitize or redact sensitive fields before writing to the log stream.

The issue is separate from CVE-2025-4166, which was a similar but distinct logging vulnerability. The root cause is likely a failure to apply consistent redaction rules across all code paths that handle malformed input. An attacker with access to the log files (e.g., via a compromised monitoring system, shared log storage, or a local privilege escalation) could extract sensitive data.

Vulnerable vs. Patched Code

The exact code changes are not publicly available, but the fix in OpenBao v2.3.0 likely involves:

• Vulnerable Code (Conceptual):

  func processRequest(req *Request) {
      log.Printf("Processing request: %+v", req)
      // ... processing logic that may fail on malformed data
  }
  

  This logs the entire request object, including any sensitive fields.

• Patched Code (Conceptual):

  func processRequest(req *Request) {
      sanitizedReq := sanitizeRequest(req) // Redacts sensitive fields
      log.Printf("Processing request: %+v", sanitizedReq)
      // ... processing logic
  }
  

  The patched version sanitizes the request before logging, ensuring that secrets are not written to logs.

Exploitation & Lab Setup

Red Team

Prerequisites:

• Access to OpenBao logs (e.g., via a shared log directory, SIEM, or a compromised monitoring agent).
• Ability to send malformed requests to the OpenBao server.

Exploitation Steps:

1. Identify the target: Locate an OpenBao instance running a version prior to 2.3.0.
2. Send malformed requests: Craft requests with intentionally broken JSON, missing fields, or invalid authentication tokens.

   curl -k -X POST https://openbao.example.com/v1/secret/data/my-secret \
     -H "X-Vault-Token: s.abc123" \
     -d '{"data": {"key": "value"}'  # Malformed JSON
   

3. Monitor logs: Check the OpenBao logs for entries that contain the sensitive data (e.g., the token or secret values).

   tail -f /var/log/openbao.log | grep -i "sensitive\|secret\|token"
   

4. Extract secrets: Parse the log entries to recover leaked credentials.

Blue Team

Detection and Prevention:

1. Upgrade immediately: Update OpenBao to version 2.3.0 or later.
2. Restrict log access: Ensure that only authorized personnel and systems can read OpenBao logs.
3. Implement log monitoring: Use a SIEM or log analysis tool to detect patterns indicative of malformed requests or leaked secrets.
4. Enable audit logging: Configure OpenBao to use a dedicated audit backend that redacts sensitive data.
5. Review existing logs: Scan historical logs for any leaked secrets and rotate affected credentials.

Indicators of Compromise (IOCs)

• Log entries containing raw secret data (e.g., tokens, passwords, certificates) in plaintext.
• Unusual patterns of malformed requests to OpenBao endpoints.
• Unexpected access to log files by non-administrative users or processes.
• Alerts from log monitoring tools indicating potential information disclosure.

Detection Engineering

YARA Rule

rule CVE_2025_52893_OpenBao_Log_Leak {
    meta:
        description = "Detects potential OpenBao log entries containing leaked secrets"
        author = "Valters IT"
        date = "2025-04-10"
        reference = "CVE-2025-52893"
    strings:
        $s1 = /[A-Za-z0-9+/]{40,}/  // Base64-like strings (potential tokens)
        $s2 = /s\.[a-zA-Z0-9]{22,}/  // Vault token pattern
        $s3 = /-----BEGIN (RSA|EC|OPENSSH) PRIVATE KEY-----/  // Private key
        $s4 = /password|secret|token|api_key/i
    condition:
        any of ($s*) and #s1 > 5  // At least 5 matches in a file
}

Sigma Rule

title: OpenBao Sensitive Data Leak in Logs
id: 7a8b9c0d-1e2f-3a4b-5c6d-7e8f9a0b1c2d
status: experimental
description: Detects potential leakage of sensitive data in OpenBao log files
author: Valters IT
date: 2025/04/10
references:
    - https://nvd.nist.gov/vuln/detail/CVE-2025-52893
logsource:
    product: linux
    service: openbao
detection:
    selection:
        EventID: 1  # Process creation (if logs are monitored via sysmon)
        Image|endswith: '/openbao'
        CommandLine|contains: 'log'
    keywords:
        - 's.'
        - '-----BEGIN'
        - 'password'
        - 'secret'
    condition: selection and keywords
falsepositives:
    - Legitimate use of tokens in logs (e.g., during debugging)
level: medium

Suricata Rule

alert http $HOME_NET any -> $EXTERNAL_NET any (msg:"CVE-2025-52893 OpenBao Malformed Request"; flow:to_server; content:"POST"; http_method; content:"/v1/"; http_uri; pcre:"/^[^{]*\{[^}]*$/"; classtype:attempted-recon; sid:1000001; rev:1;)

Remediation & Mitigation

1. Immediate Action: Upgrade all OpenBao instances to version 2.3.0 or later.
2. Log Rotation and Retention: Implement strict log rotation and retention policies to limit the exposure window.
3. Access Control: Restrict access to log files using file permissions and SELinux/AppArmor profiles.
4. Audit Backend: Configure OpenBao to use a dedicated audit backend (e.g., syslog, file) with redaction enabled.
5. Monitor for Malformed Requests: Deploy WAF rules or API gateways to reject malformed requests before they reach OpenBao.
6. Credential Rotation: Rotate any secrets that may have been exposed in logs prior to patching.

Valters IT