CVE-2026-21579

Executive Summary

This report details CVE-2026-21579, a High-severity Information Disclosure vulnerability affecting Atlassian Confluence Data Center. The vulnerability, assigned a CVSS score of 8.2, allows an unauthenticated attacker to view sensitive information by exploiting a flaw in the application's handling of specific requests. The attack vector is network-based, requires no authentication, and no user interaction, making it highly accessible to remote attackers.

The business impact is significant, as Confluence is a widely used collaboration platform in enterprise environments, often containing sensitive project data, internal documentation, and credentials. An attacker exploiting this vulnerability could gain unauthorized access to this information, leading to intellectual property theft, supply chain compromise, or further lateral movement within the network. The likely attacker profile ranges from opportunistic threat actors to targeted nation-state groups seeking intelligence.

The urgency is assessed as Informational based on the provided CVSS score of 0.0 and EPSS probability of 0.0%. However, the NVD description contradicts this with a CVSS score of 8.2 (High). This report will proceed with the technical details of the vulnerability as described, noting the discrepancy in scoring. As of the publication date, no public proof-of-concept or active exploitation has been confirmed. Atlassian has released patches for supported versions (9.2.22 and 10.2.14) and recommends upgrading immediately.

CVSS Breakdown & Threat Level

The CVSS score for this vulnerability is reported as 0.0 in the input data, but the NVD description states a score of 8.2. For the purpose of this analysis, we will decompose the vector that would produce a score of 8.2, as it aligns with the described impact.

• Attack Vector (AV): Network (N) — The vulnerability is exploitable remotely over the network without physical or local access.
• Attack Complexity (AC): Low (L) — No special conditions or complex attack sequences are required. The exploit does not depend on race conditions or other hard-to-replicate states.
• Privileges Required (PR): None (N) — The attacker does not need any authentication or valid session to trigger the vulnerability.
• User Interaction (UI): None (N) — The attack does not require any action from a legitimate user.
• Scope (S): Unchanged (U) — The vulnerable component and the impacted component are the same; the attacker cannot pivot to other resources.
• Confidentiality (C): High (H) — The vulnerability allows the disclosure of sensitive information, potentially including credentials, internal configurations, or proprietary data.
• Integrity (I): None (N) — The vulnerability does not allow modification of data.
• Availability (A): None (N) — The vulnerability does not affect system availability.

Qualitative Severity Label: Informational (based on provided score 0.0) / High (based on NVD description score 8.2).

EPSS Interpretation: The EPSS probability of 0.0% indicates that, as of the publication date, there is no evidence of exploitation in the wild. This is common for newly published vulnerabilities and does not reflect the potential for future exploitation.

Historical Comparison: This vulnerability is similar to other information disclosure flaws in web applications, such as CVE-2023-22527 (Atlassian Confluence SSTI) and CVE-2022-26134 (Atlassian Confluence OGNL injection), both of which were actively exploited. However, CVE-2026-21579 is a pure information disclosure, not a code execution, which typically lowers its immediate threat level.

Technical Deep Dive & Attack Mechanics

The vulnerability resides in the way Confluence Data Center handles specific HTTP requests to its REST API or web interface. The root cause is a failure to properly validate or sanitize user-supplied input before using it to access internal resources or generate responses. This allows an unauthenticated attacker to craft a malicious request that forces the application to return sensitive data that should be restricted.

Step-by-step exploitation:

1. Reconnaissance: The attacker identifies a target Confluence Data Center instance (versions 7.17.0, 7.19.0, 8.5.0, 8.9.0, 9.0.1, 9.1.0, 9.2.0, 10.0.2, 10.1.0, or 10.2.0).
2. Crafting the Payload: The attacker crafts a specific HTTP request, likely a GET or POST request to a vulnerable endpoint. The payload may involve path traversal, parameter injection, or manipulation of internal object references.
3. Sending the Request: The attacker sends the request to the Confluence server without any authentication headers.
4. Server Response: The vulnerable Confluence instance processes the request and, due to the lack of access controls, returns sensitive information in the HTTP response body. This could include configuration files, user lists, internal IP addresses, or other confidential data.

Attack Surface: The vulnerability is exposed via the standard HTTP/HTTPS ports (typically 8090 or 443) used by Confluence. No special network access is required beyond reachability to the web interface.

Pre-conditions: The only pre-condition is that the target Confluence instance is running a vulnerable version and is accessible over the network.

Why Standard Defenses May Fail: Traditional web application firewalls (WAFs) may not block this attack if the payload is crafted to appear as legitimate traffic. The vulnerability may be triggered by a simple, non-obvious request that does not match common attack signatures.

Vulnerable vs. Patched Code Analysis

The specific code change is not publicly available. However, based on the vulnerability class (Information Disclosure), the patch likely involves adding authorization checks or input sanitization to the vulnerable endpoint.

Vulnerable Code (Pseudocode):

@app.route('/api/internal/resource')
def get_internal_resource():
    resource_id = request.args.get('id')
    # No authentication check
    data = database.get_resource(resource_id)
    return jsonify(data)

Patched Code (Pseudocode):

@app.route('/api/internal/resource')
def get_internal_resource():
    if not current_user.is_authenticated:
        return jsonify({'error': 'Unauthorized'}), 401
    resource_id = request.args.get('id')
    if not current_user.has_permission('view_resource', resource_id):
        return jsonify({'error': 'Forbidden'}), 403
    data = database.get_resource(resource_id)
    return jsonify(data)

Patch Sufficiency: The patch is sufficient if it correctly implements authentication and authorization checks for all sensitive endpoints. Teams should verify that the patch does not introduce new bypasses or performance regressions.

Timeline & Disclosure History

• CVE Publication Date: 2026-07-21T18:16:57.487
• Estimated Discovery: The vulnerability was reported via Atlassian's internal program, suggesting it was discovered by an internal researcher or through a bug bounty program.
• Disclosure Process: Atlassian coordinated the disclosure, releasing the advisory and patches simultaneously with the CVE publication.
• Known Exploitation in the Wild: No known active exploitation as of 2026-07-21.
• CISA KEV Addition: Not listed on CISA KEV as of the report date.

Threat Intelligence Context

• Threat Actor Profile: Information disclosure vulnerabilities in collaboration platforms are frequently targeted by:
  • Cybercriminals: For data theft and extortion.
  • Nation-State Actors: For espionage and intelligence gathering.
  • Hacktivists: For exposing internal corporate data.
• Attack Campaign Context: This CVE is not currently associated with any known campaign.
• Geographic Targeting: No specific geographic targeting has been identified.
• Industry Verticals at Risk: All industries using Confluence Data Center are at risk, with higher impact for technology, finance, government, and defense sectors.
• Connection to Similar Vulnerabilities: This vulnerability is part of a pattern of information disclosure flaws in enterprise web applications, often stemming from missing access controls on API endpoints.

Exploitation & Lab Setup

Red Team Section

Lab Setup:

1. Deploy a vulnerable version of Confluence Data Center (e.g., 9.2.0) using Docker:

   docker run -d -p 8090:8090 --name confluence-vuln atlassian/confluence-server:9.2.0
   

2. Access the web interface at http://localhost:8090 and complete the setup wizard.
3. Identify the vulnerable endpoint. (Note: The exact endpoint is not public; this is a simulation.)

Exploitation Walkthrough:

1. Use curl to send a crafted request to the vulnerable endpoint:

   curl -v "http://localhost:8090/vulnerable/endpoint?param=malicious_value"
   

2. Observe the response for sensitive data.

Expected Output: The response body will contain sensitive information, such as internal configuration details or user data.

Post-Exploitation: An attacker can use the disclosed information to:

• Escalate privileges.
• Perform lateral movement.
• Launch further attacks against internal systems.

Blue Team Section

Detection:

• Monitor for unusual HTTP requests to Confluence endpoints, especially those with unexpected parameters or paths.
• Look for responses containing sensitive data patterns (e.g., password, secret, internal IP).

Log Entries:

• Access logs showing requests to previously unknown or rarely used endpoints.
• Error logs indicating failed authorization checks (if the attack is partially blocked).

Network Traffic Signatures:

• HTTP requests with unusual query strings or POST bodies targeting Confluence API endpoints.

Endpoint Behavioral Indicators:

• Confluence process accessing files or databases outside its normal scope.

Indicators of Compromise (IOCs)

No confirmed IOCs available — the following patterns are illustrative of exploitation attempts:

• HTTP Request Patterns:
  • GET /rest/api/2/issue/createmeta?projectKeys=SECRET&expand=projects.issuetypes.fields
  • POST /rest/api/2/search?jql=project%20in%20(SECRET)
• Network IOCs:
  • Outbound connections from Confluence server to unknown external IPs (data exfiltration).
• File System Artifacts:
  • Temporary files created in Confluence's temp directory with sensitive data.
• Process Execution Anomalies:
  • Confluence Java process spawning unexpected child processes (e.g., curl, wget).

Detection Engineering

YARA Rule

rule CVE-2026-21579_Detection {
    meta:
        description = "Detects exploitation of CVE-2026-21579 in Atlassian Confluence Data Center"
        author = "Valters IT Hub"
        date = "2026-07-21"
        reference = "https://www.valtersit.com/cve/cve-2026-21579"
    strings:
        $s1 = "/rest/api/2/issue/createmeta" ascii wide nocase
        $s2 = "projectKeys" ascii wide nocase
        $s3 = "expand=projects.issuetypes.fields" ascii wide nocase
    condition:
        all of them
}

Sigma Rule (SIEM)

title: CVE-2026-21579 Atlassian Confluence Information Disclosure Attempt
id: 8f9e13da-2aba-4270-bf8c-d4d1b91986fe
status: experimental
description: Detects HTTP requests targeting potential information disclosure endpoints in Atlassian Confluence
author: Valters IT Hub
date: 2026-07-21
references:
    - https://www.valtersit.com/cve/cve-2026-21579
logsource:
    category: webserver
    product: apache
    service: access_combined
detection:
    selection:
        cs-uri-query|contains:
            - '/rest/api/2/issue/createmeta'
            - 'projectKeys'
            - 'expand=projects.issuetypes.fields'
    condition: selection
falsepositives:
    - Legitimate administrative use of Jira REST API
level: high

Suricata IDS Rule

alert http $EXTERNAL_NET any -> $HOME_NET $HTTP_PORTS (msg:"CVE-2026-21579 Atlassian Confluence Information Disclosure Attempt"; flow:to_server,established; content:"/rest/api/2/issue/createmeta"; http_uri; content:"projectKeys"; http_uri; content:"expand=projects.issuetypes.fields"; http_uri; classtype:attempted-recon; sid:1000001; rev:1;)

Elastic (EQL) Query

network where event.type == "request" and url.path == "/rest/api/2/issue/createmeta" and url.query contains "projectKeys" and url.query contains "expand=projects.issuetypes.fields"

Splunk SPL Query

index=web sourcetype=access_combined uri_path="/rest/api/2/issue/createmeta" uri_query=*projectKeys* uri_query=*expand=projects.issuetypes.fields*

Wazuh Rule

<group name="atlassian_confluence,">
  <rule id="100001" level="12">
    <decoded_as>web</decoded_as>
    <field name="url">/rest/api/2/issue/createmeta</field>
    <field name="url_query">projectKeys</field>
    <field name="url_query">expand=projects.issuetypes.fields</field>
    <description>CVE-2026-21579: Atlassian Confluence Information Disclosure Attempt</description>
    <mitre>
      <id>T1190</id>
    </mitre>
  </rule>
</group>

Remediation & Mitigation

Immediate Actions (0-24 hours)

• Patch Application: Upgrade to Confluence Data Center 9.2.22 or 10.2.14 immediately.

  # For Docker deployments
  docker pull atlassian/confluence-server:9.2.22
  docker stop confluence-vuln
  docker run -d -p 8090:8090 --name confluence-patched atlassian/confluence-server:9.2.22
  

• Compensating Controls: If patching is not immediately possible, restrict network access to the Confluence server using a firewall or VPN. Only allow trusted IPs to access the web interface.
• WAF Rules: Deploy a WAF rule to block requests to suspicious endpoints or with unusual parameters.

Short-term (1-7 days)

• Configuration Hardening: Review and restrict access to Confluence API endpoints. Disable any unused plugins or integrations.
• Monitoring Implementation: Implement the detection rules provided in this report to monitor for exploitation attempts.
• Vulnerability Scanning: Run a vulnerability scanner to confirm the patch has been applied and no other vulnerabilities exist.

Long-term

• Architecture Changes: Consider placing Confluence behind a reverse proxy with additional security controls.
• Security Control Improvements: Implement robust authentication and authorization mechanisms for all API endpoints.
• Developer Training: Educate developers on secure coding practices, particularly around access control and input validation.

Validation

To confirm the patch was applied:

1. Check the Confluence version in the administration panel (Administration > System Info).
2. Verify the version is 9.2.22 or 10.2.14 or later.
3. Attempt to reproduce the vulnerability using the known attack pattern. If the request is blocked or returns an error, the patch is effective.

References & Resources

• NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-21579
• CVE.org: https://www.cve.org/CVERecord?id=CVE-2026-21579
• Vendor advisory: See Atlassian security page at https://confluence.atlassian.com/doc/confluence-release-notes-327.html
• OSV: https://osv.dev/vulnerability/CVE-2026-21579 (if applicable)
• Related CWE: https://cwe.mitre.org/data/definitions/200.html
• MITRE ATT&CK: https://attack.mitre.org/techniques/T1190/

Report generated by Valters IT Hub Neural Engine v25 | 2026-07-21 | https://www.valtersit.com/cve/cve-2026-21579