CVE-2026-102407

Executive Summary

CVE-2026-102407 is an Incorrect Authorization vulnerability (CWE-863) in Elasticsearch that allows an authenticated user holding privileges over a single resource to abuse the Modify Data Streams API to alter a data stream they are not authorized to modify. The flaw stems from access-control checks that fail to properly constrain access to the Modify Data Streams functionality, enabling unauthorized data stream modification — including potential data injection or disruption of normal searchability. It does not permit reading the contents of a data stream the attacker cannot otherwise access, and the CVSS base score is 5.4 (Medium).

Technical Analysis

The vulnerability is classified as CWE-863: Incorrect Authorization, and mapped by the CNA to CAPEC-1 (Accessing Functionality Not Properly Constrained by ACLs). The core defect is an authorization boundary failure: the Modify Data Streams API path does not correctly enforce the privileges required for the specific data stream being targeted.

Per the NVD description, an authenticated user who holds "sufficient privileges over a single resource" can invoke the Modify Data Streams API against a data stream to which they are not otherwise authorized. This indicates the authorization logic validates that the caller possesses some privilege but fails to scope that privilege to the correct target resource — a classic horizontal/vertical authorization gap where resource-level access control is missing or misapplied.

The consequence of successful abuse is modification of a data stream the attacker should not control. The description explicitly states two impact classes:

1. Data injection into the targeted data stream.
2. Affecting the data stream's ability to be searched normally (i.e., availability/integrity of the searchable data).

The description also draws a clear boundary: the issue does not allow an attacker to read the contents of a data stream they do not otherwise have access to. This is corroborated by the CVSS vector, where Confidentiality impact is None (C:N). Integrity and Availability impacts are both Low (I:L / A:L), and the attack requires a network vector (AV:N), low complexity (AC:L), low privileges (PR:L), and no user interaction (UI:N). Scope is Unchanged (S:U), meaning the vulnerable component's authorization failure does not cross a security authority boundary beyond the impacted component.

No specific function names, internal class names, API parameters, or code paths beyond "Modify Data Streams API" are provided in the source data; therefore this report does not attribute behavior to internal implementation details that are not disclosed.

Exploitation Scenarios

The following attack chain is derived strictly from the NVD description and the associated vulnerability class. No public PoC, exploit code, or Nuclei template exists for this CVE, so the chain is inferred at the vulnerability-class level.

1. Reconnaissance / target identification. The attacker requires authenticated access to an Elasticsearch cluster (PR:L — a low-privileged account is sufficient). The attacker enumerates data streams present in the cluster and identifies a target data stream for which they hold privileges over a different resource but not over the target. This enumeration is consistent with a legitimate authenticated user mapping the cluster's data streams.

2. Triggering the flaw class. The attacker invokes the Modify Data Streams API. Because the authorization check fails to properly constrain that functionality to the caller's authorized resources (the CWE-863 / CAPEC-1 condition), the request is not correctly rejected for the out-of-scope data stream.

3. Payload / execution method. At the vulnerability-class level, the attacker submits a modification request through the Modify Data Streams API targeting the unauthorized data stream. The description does not disclose the exact request parameters used, so no specific payload structure can be asserted. The exploitable primitive is unauthorized modification of a data stream configuration or contents; the attacker may aim to inject data or to alter the data stream so that it cannot be searched normally.

4. Post-exploitation impact. Successful exploitation yields unauthorized integrity modification of the targeted data stream (potential data injection) and availability degradation of search functionality on that stream. The attacker cannot, per the disclosure, read data stream contents they were not already authorized to read — so this is not a data-exfiltration primitive.

No public exploit or in-the-wild exploitation evidence is available for this CVE.

Impact Assessment

• Integrity (Low, I:L): An attacker can modify a data stream they are not authorized to change, with the potential to inject data. This directly undermines trust in the tampered data stream and any analytics, detections, or dashboards consuming it.
• Availability (Low, A:L): Modification can affect the data stream's ability to be searched normally, degrading search/query availability for legitimate consumers of that stream.
• Confidentiality (None, C:N): No unauthorized read access is granted; the flaw does not expose data stream contents.
• Privileges required (PR:L): Any authenticated user with privileges over at least one resource can potentially exploit this, widening the attacker pool to include legitimate but lower-privileged accounts.

Business impact: In environments where Elasticsearch indexes underpin security monitoring (SIEM), observability, or business analytics, unauthorized modification of a data stream can silently corrupt or degrade the integrity of security telemetry and operational data. Data injection into telemetry streams could be leveraged for detection evasion or data poisoning, even though the flaw alone does not enable data theft. The blast radius is bounded by the specific unauthorized data streams an attacker can reach and by the requirement for prior authentication. Given the Medium severity (5.4) and no confirmed exploitation, this should be prioritized as part of authorization-hardening and access-review work rather than as an emergency internet-exposed RCE-class issue.

Detection Guidance

Sigma Rule

title: Potential Elasticsearch Modify Data Streams API Authorization Abuse
id: 7f3c1a2e-elasticsearch-datastream-modify-cve2026-102407
status: experimental
description: Detects calls to the Elasticsearch Modify Data Streams API that may indicate abuse of incorrect authorization (CWE-863) to modify an unauthorized data stream.
references:
  - https://nvd.nist.gov/vuln/detail/CVE-2026-102407
author: Valters IT Threat Intelligence
date: 2026-01-01
logsource:
  category: webserver
  product: elasticsearch
detection:
  selection_api:
    cs-method: 'POST'
    cs-uri-stem|contains: '/_data_stream/'
  selection_functionality:
    cs-uri-query|contains: 'modify'
  condition: selection_api
fields:
  - c-ip
  - cs-username
  - cs-uri-stem
  - cs-uri-query
falsepositives:
  - Legitimate administrative data stream management by authorized operators
level: low

Note: The exact URI parameters for the Modify Data Streams API are not disclosed in the source data; the rule keys on the data stream endpoint family and should be tuned against observed legitimate administrative traffic.

YARA Rule

rule CVE_2026_102407_Elasticsearch_DataStream_Modify_AuthBypass
{
    meta:
        description = "Detects references to the Elasticsearch Modify Data Streams API associated with CVE-2026-102407 authorization bypass"
        author = "Valters IT Threat Intelligence"
        reference = "https://nvd.nist.gov/vuln/detail/CVE-2026-102407"
        date = "2026-01-01"
        severity = "medium"

    strings:
        $api = "_data_stream" ascii nocase
        $modify = "modify" ascii nocase
        $cve = "CVE-2026-102407" ascii nocase

    condition:
        uint16(0) == 0x5090 or (any of ($api, $modify)) or $cve
}

Note: This rule targets textual references to the data stream endpoint; it is intended for log, threat-hunt artifact, and forensic scanning rather than compiled-binary detection, as no binary indicator is disclosed.

Suricata IDS Rule

alert http any any -> any any (msg:"CVE-2026-102407 Potential Elasticsearch Modify Data Streams API Authorization Abuse"; flow:established,to_server; http.method; content:"POST"; http.uri; content:"/_data_stream/"; nocase; reference:cve,2026-102407; reference:url,nvd.nist.gov/vuln/detail/CVE-2026-102407; classtype:attempted-user; sid:2026102407; rev:1;)

Note: The rule monitors HTTP requests to the data stream endpoint. Adjust to TLS-inspection feeds as needed; cleartext observation only.

Elastic Detection

sequence by user.name, source.ip with maxspan=5m
  [authentication where event.outcome == "success" and user.name != null]
  [http where http.request.method == "POST" and
   http.request.uri : "*/_data_stream/*"]

Note: EQL keys on an authenticated session followed by a data stream modification request. The intent is to surface lower-privileged accounts performing data stream modification operations. Tune the URI pattern to the deployment's API surface.

Splunk SPL Query

index=elasticsearch OR index=web
| search (uri="/_data_stream/*" OR url="/_data_stream/*")
| eval method=coalesce(http_method, method)
| where method="POST"
| stats count min(_time) as first_seen max(_time) as last_seen
        by src_ip, user, uri
| where count > 0
| sort - count

Note: Detects POST requests against the data stream endpoint. Correlate user against an allowlist of authorized data stream administrators to reduce false positives.

Wazuh OSSEC Rule

<group name="elasticsearch,CVE-2026-102407,">
  <rule id="102407" level="6">
    <decoded_as>json</decoded_as>
    <field name="method">POST</field>
    <field name="url">\.?/_data_stream/.*</field>
    <description>CVE-2026-102407: Potential Elasticsearch Modify Data Streams API authorization abuse</description>
    <mitre>
      <id>T1078</id>
    </mitre>
  </rule>
</group>

Note: This rule assumes Elasticsearch access logs are decoded as JSON and routed to Wazuh. Adjust <field> names to match the deployment's log schema.

Mitigation & Patch Guidance

Patch confidence: 0/4 — UNPATCHED. No patch evidence exists from any tracked source, and no vendor fix or affected version range is published in the provided intelligence data.

1) Immediate mitigations (compensating controls):

• Enforce least privilege on Elasticsearch roles. Review and restrict which roles can invoke the Modify Data Streams API, ensuring no role grants data stream modification rights broader than intended.
• Apply the principle of resource scoping: verify that user roles mapping to data streams are explicitly limited to the streams they legitimately require.
• Monitor and alert on all Modify Data Streams API invocations (see Detection Guidance) and correlate against a known-good administrator allowlist.
• Where possible, restrict network access to the Elasticsearch API (port 9200) to trusted management networks; do not expose the cluster API to untrusted networks.

2) Patch/upgrade steps:

• No patched version is currently identified. Monitor the Elastic Elasticsearch security advisories and the NVD entry for CVE-2026-102407 for an official fix and affected-version range.
• Once a fix is published, stage, test, and deploy the upgrade in line with change-management procedures, then re-validate that data stream modification is correctly constrained by authorization.

3) Long-term hardening:

• Implement continuous access reviews of Elasticsearch roles and role mappings, with periodic validation that resource-level authorization matches business need.
• Adopt automated authorization regression testing for sensitive APIs such as Modify Data Streams.
• Maintain robust audit logging of all data stream management operations and forward logs to a tamper-resistant SIEM pipeline.
• Track CVE-2026-102407 in vulnerability management tooling and re-score impact once a patch and EPSS data become available.

References

1. NVD — CVE-2026-102407: https://nvd.nist.gov/vuln/detail/CVE-2026-102407
2. CWE-863 — Incorrect Authorization: https://cwe.mitre.org/data/definitions/863.html
3. CAPEC-1 — Accessing Functionality Not Properly Constrained by ACLs: https://capec.mitre.org/data/definitions/1.html
4. Elastic Security Advisories (monitor for CVE-2026-102407 patch): https://www.elastic.co/community/security
5. CISA Known Exploited Vulnerabilities Catalog (no entry for CVE-2026-102407 as of this report): https://www.cisa.gov/known-exploited-vulnerabilities-catalog

No known threat actor campaigns or exploit-in-the-wild evidence have been associated with CVE-2026-102407 at the time of writing.