CVE-2026-18061

Executive Summary

CVE-2026-18061 is an XML External Entity (XXE) injection vulnerability (CWE-611) affecting the RemoteQueryCachePlugin in AWS Advanced JDBC Wrapper versions 3.3.0 through 4.2.0. An attacker with write access to the shared cache infrastructure can inject crafted XML data into a cached column value, potentially leading to the disclosure of sensitive files on application hosts. The vulnerability has a CVSS score of 5.9, indicating a moderate severity level with high confidentiality impact.

Technical Analysis

The vulnerability resides in the RemoteQueryCachePlugin component of the AWS Advanced JDBC Wrapper. This plugin is designed to cache database query results in a shared infrastructure (such as Redis or another remote cache) to improve performance and reduce database load. The flaw is an instance of CWE-611: Improper Restriction of XML External Entity References.

When the wrapper retrieves cached query results, it parses the cached data. If the cached column value contains crafted XML data that includes external entity references, and the XML parser is not configured to disable external entity resolution, the parser will attempt to resolve these entities. This can cause the application host to read local files and include their contents in the parsed result. The description explicitly notes that this could lead to the disclosure of "stored database and IAM role credentials." These credentials are often stored in configuration files or environment variables on application hosts. By injecting a malicious XML payload into the cache, an attacker with write access to the cache infrastructure can exfiltrate these sensitive files.

The attack requires the attacker to have write access to the shared cache infrastructure, which is a significant precondition. This suggests the vulnerability is most likely to be exploited by an insider threat, a compromised cache service, or an attacker who has already gained a foothold in the network. The CVSS vector CVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:U/C:H/I:N/A:L reflects that the attack is network-based (AV:N), requires high complexity (AC:H) due to the need for cache write access and specific conditions, requires low privileges (PR:L) on the cache, requires no user interaction (UI:N), and results in high confidentiality impact (C:H) with low availability impact (A:L).

The vulnerability was addressed in version 4.3.0 of the AWS Advanced JDBC Wrapper. Users are advised to upgrade to this version or later. As of this report, no public proof-of-concept (PoC) or exploit code is available, and the vulnerability has not been listed in CISA's Known Exploited Vulnerabilities (KEV) catalog. The EPSS score has not yet been assigned by FIRST.org.

Exploitation Scenarios

1. Reconnaissance and Target Identification: An attacker first identifies an application that uses the AWS Advanced JDBC Wrapper version 3.3.0 to 4.2.0 with the RemoteQueryCachePlugin enabled and configured to use a shared cache (e.g., Redis, Memcached). The attacker then needs to gain write access to that cache. This could be achieved through compromised credentials, misconfigured access controls, or a separate vulnerability in the cache infrastructure.

2. Triggering the XXE Flaw: Once write access is obtained, the attacker crafts an XML payload that includes an external entity reference. For example, an XML document with a DOCTYPE declaration defining an entity that references a local file, such as file:///etc/passwd or a path to a credentials file. This payload is then inserted into the cache as a value for a key that the application will later read as a cached column value for a query result. The exact format of the cache key and value depends on the RemoteQueryCachePlugin's implementation, which is not detailed in the available description.

3. Payload Execution: When the application executes a query that hits the cache, the RemoteQueryCachePlugin retrieves the cached data. If the cached data contains the malicious XML, the XML parser processes it. Due to the lack of external entity restrictions, the parser resolves the external entity, reading the specified local file and embedding its content into the parsed result. The application may then log this result, return it to a user, or otherwise expose the file contents.

4. Post-Exploitation Impact: The attacker can exfiltrate sensitive files from the application host. According to the NVD description, this includes "stored database and IAM role credentials." With these credentials, the attacker can escalate privileges, access databases, or move laterally within the AWS environment by assuming IAM roles. The impact is primarily confidentiality loss, though availability impact is low (A:L). The scope is unchanged (S:U), meaning the vulnerability does not affect resources beyond the application host's security scope, but the leaked credentials could be used to compromise other systems.

No public PoC is available; the attack chain is inferred from the vulnerability class (XXE) and the specific context of the cache plugin.

Impact Assessment

The business impact of CVE-2026-18061 is significant for organizations using the affected AWS Advanced JDBC Wrapper. The high confidentiality impact (C:H) means that sensitive credentials, such as database passwords and IAM role credentials, can be exposed. This could lead to unauthorized access to databases, cloud resources, and further lateral movement within the AWS environment. The low availability impact (A:L) suggests that the exploit might cause minor disruptions, such as parsing errors or application crashes, but the primary risk is data theft.

The attack surface is limited to applications that use the RemoteQueryCachePlugin with a shared cache and where the cache has been compromised or is accessible to unauthorized writers. The blast radius can extend beyond the initial application host because leaked IAM credentials can be used to access other AWS services. However, the high attack complexity (AC:H) and the prerequisite of low privileges on the cache (PR:L) make mass exploitation less likely. The lack of public exploit code and KEV listing suggests that exploitation is not currently widespread.

Detection Guidance

Sigma Rule

title: AWS Advanced JDBC Wrapper XXE Exploitation Attempt
id: 8f9a2b1c-3d4e-5f6a-7b8c-9d0e1f2a3b4c
status: experimental
description: Detects potential XXE exploitation attempts against the RemoteQueryCachePlugin in AWS Advanced JDBC Wrapper
author: Valters IT
date: 2026/07/27
references:
  - https://nvd.nist.gov/vuln/detail/CVE-2026-18061
logsource:
  category: application
  product: aws_jdbc_wrapper
detection:
  selection:
    EventID: 1000  # Example event ID for XML parsing errors
    Message|contains:
      - 'DOCTYPE'
      - 'ENTITY'
      - 'SYSTEM'
  condition: selection
falsepositives:
  - Legitimate XML processing with external entities
level: high

YARA Rule

rule CVE_2026_18061_XXE_Payload
{
    meta:
        description = "Detects XML external entity payloads targeting CVE-2026-18061"
        author = "Valters IT"
        date = "2026-07-27"
        reference = "https://nvd.nist.gov/vuln/detail/CVE-2026-18061"
        severity = "high"
    strings:
        $xxe1 = "<!DOCTYPE" nocase
        $xxe2 = "<!ENTITY" nocase
        $xxe3 = "SYSTEM" nocase
        $file1 = "file://" nocase
        $file2 = "php://filter" nocase
    condition:
        uint16(0) == 0x3C3F or uint16(0) == 0x3C21 or uint16(0) == 0x3C45
        and any of ($xxe*)
        and any of ($file*)
}

Suricata IDS Rule

alert tcp any any -> any any (msg:"CVE-2026-18061 AWS JDBC Wrapper XXE Attempt"; flow:to_server,established; content:"<!DOCTYPE"; nocase; content:"<!ENTITY"; nocase; distance:0; content:"SYSTEM"; nocase; distance:0; reference:cve,2026-18061; classtype:attempted-recon; sid:1000001; rev:1;)

Elastic Detection

process where event.type == "start" and process.name == "java" and
  process.args : "*RemoteQueryCachePlugin*" and
  process.args : ("*DOCTYPE*" or "*ENTITY*" or "*SYSTEM*")

Splunk SPL Query

index=main sourcetype=aws_jdbc_wrapper
| search "RemoteQueryCachePlugin" AND ("DOCTYPE" OR "ENTITY" OR "SYSTEM")
| stats count by host, user, process

Wazuh OSSEC Rule

<group name="aws_jdbc_wrapper,">
  <rule id="100001" level="12">
    <decoded_as>json</decoded_as>
    <field name="message">RemoteQueryCachePlugin</field>
    <field name="message">DOCTYPE</field>
    <description>CVE-2026-18061: Potential XXE exploitation attempt in AWS Advanced JDBC Wrapper</description>
    <mitre>
      <id>T1190</id>
    </mitre>
  </rule>
</group>

Mitigation & Patch Guidance

Patch confidence: 0/4 (UNPATCHED — no patch evidence from any tracked source).

1. Immediate Mitigations:

   • Restrict write access to the shared cache infrastructure to trusted components only.
   • Implement network segmentation to limit access to the cache.
   • Monitor cache write operations for anomalous XML content.
   • If feasible, disable the RemoteQueryCachePlugin until an upgrade can be performed.

2. Patch/Upgrade Steps:

   • Upgrade to AWS Advanced JDBC Wrapper version 4.3.0 or later. This version addresses the improper restriction of XML external entity references.
   • After upgrading, verify that the RemoteQueryCachePlugin is functioning correctly and that XML parsing is secure.

3. Long-Term Hardening:

   • Regularly update dependencies and monitor for security advisories.
   • Implement strict input validation and sanitization for any data stored in caches.
   • Use a secure XML parser configuration that disables external entity resolution (e.g., set disallow-doctype-decl to true).
   • Conduct security reviews of third-party libraries and their configurations.

References

• NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-18061
• AWS Security Advisory: (No specific advisory available; check AWS security bulletins for updates)
• CWE-611: https://cwe.mitre.org/data/definitions/611.html
• OWASP XXE Prevention Cheat Sheet: https://cheatsheetseries.owasp.org/cheatsheets/XML_External_Entity_Prevention_Cheat_Sheet.html
• GitHub Advisory Database: (No entry available at this time)

No known threat actor campaigns or exploit-in-the-wild evidence has been observed for this vulnerability.