CVE-2026-76389

Executive Summary

CVE-2026-76389 describes a server-side request forgery (SSRF) vulnerability located in Cisco Talos Intelligence for Splunk Enterprise Security Cloud versions below 1.0.3. An authenticated user possessing the get_talos_enrichment capability can send crafted requests to the Talos intelligence enrichment REST API endpoint, forcing the Splunk instance to initiate outbound HTTP requests to an attacker-controlled server. Successful exploitation exposes authentication tokens that compromise the confidentiality, integrity, and availability of the Splunk instance and its associated data, with a CVSS base score of 8.8 (High). The vulnerability remains unpatched with no known public exploit code, yet the potential for token compromise makes immediate remediation planning essential.

Technical Analysis

The vulnerability is classified under CWE-918, Server-Side Request Forgery, and manifests in the Splunk Enterprise Security Cloud product line — specifically in versions below 1.0.3 of the Cisco Talos Intelligence enrichment add-on. The affected component is the Talos intelligence enrichment REST API endpoint accessible through the Splunk management interface.

The root cause is a failure to separate trusted server-side configuration from untrusted request-supplied data. The Talos intelligence enrichment REST endpoint accepts the destination for authenticated Splunk management requests directly from request data supplied by the user. In a properly designed system, the destination endpoint for server-to-server communications would be defined in immutable server-side configuration (e.g., a configuration file or environment variable). Here, the destination is derived from client-controlled request payloads, enabling the server to issue authenticated outbound requests to arbitrary hosts and ports selected by the attacker.

The attacker must first authenticate to the Splunk instance and possess a role that includes the get_talos_enrichment capability. This capability is presumably granted only to security analyst or administrator roles; however, its existence implies that at least a subset of standard users can invoke the enrichment functions. The attack does not require special network positioning — the CVSS vector reflects this with AV:N (network attack vector) and PR:L (low privilege requirement), meaning a low-privileged authenticated user can trigger the flaw over the network without user interaction (UI:N).

The attack mechanics at the protocol level: the authenticated user crafts an HTTP request to the Talos enrichment REST endpoint, embedding a destination URL (attacker-controlled) within the request data. The Splunk instance, acting as a client, then sends an authenticated management request to that attacker-controlled destination. Because Splunk's management REST API may attach authentication tokens or session cookies to outbound requests, the attacker's server can harvest these tokens upon receipt of the request. The scope of the compromise spans confidentiality (token leakage), integrity (attacker may use tokens to modify data), and availability (attacker may disrupt or delete data) — reflected in the scoped CVSS vector with S:U and C:H/I:H/A:H.

Insufficient technical detail is available in the NVD description regarding the exact request format, parameter names, or header structure. No specific API endpoints, function names, or file paths are provided beyond the generic "Talos intelligence enrichment Representational State Transfer (REST) API endpoint." Consequently, the precise request structure, HTTP method, or query string format cannot be disclosed with confidence. Further technical analysis is constrained by the absence of vendor advisory details, patch notes, or exploit code.

Exploitation Scenarios

No public PoC exists for this vulnerability; the attack chain is inferred from the vulnerability class (CWE-918 SSRF) and the NVD description. The following scenario is reconstructed at the vulnerability-class level without fabricating implementation details:

Step 1 — Reconnaissance / Target Identification: An attacker first identifies a target Splunk Enterprise Security Cloud instance running the Talos Intelligence add-on at a version below 1.0.3. This can be achieved by banner grabbing, examining the Splunk web interface's version disclosure, or probing for the Talos enrichment REST API endpoint. The attacker also requires valid credentials for an account with a role that includes the get_talos_enrichment capability — potentially obtained through credential stuffing, phishing of SOC analysts, or insider access.

Step 2 — Flaw Class Trigger: The attacker authenticates to the Splunk instance and crafts an HTTP request to the Talos intelligence enrichment REST API endpoint. Critically, the request includes a destination for an authenticated Splunk management request that is supplied in the request data itself. Because the endpoint accepts this destination from user-controlled data, the attacker substitutes the legitimate Talos enrichment target with the URL of an attacker-controlled server.

Step 3 — Payload / Execution Method: The attacker's crafted request causes the Splunk instance to initiate an outbound HTTP connection to the attacker's server. The request carries authentication context — likely in the form of session tokens, API keys, or management credentials — that the benign system would ordinarily present to the legitimate Talos intelligence service. The attacker's server captures these tokens. This step does not require any injection of malicious code into Splunk; the flaw is purely a logic/design deficiency in accepting the destination from request data.

Step 4 — Post-Exploitation Impact: Having obtained valid authentication tokens, the attacker can replay them against the Splunk instance's management API to perform arbitrary actions. Depending on the privileges associated with the stolen tokens, this may include: reading or exfiltrating indexed security data, modifying log sources, disabling detection rules, deleting forensic data, or pivoting to other systems integrated with Splunk. Because the tokens may carry administrative or high-privilege context, the extent of compromise can escalate to full control over the Splunk instance — violating data confidentiality, integrity, and availability.

The attack chain is thus: authentication → crafted SSRF request → token exfiltration → privileged access → data compromise. It is entirely plausible that this chain can be executed without generating suspicious artifacts on the host, as the requests originate from legitimate Splunk processes.

Impact Assessment

The CVSS base score of 8.8 (High) with vector CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H quantifies the severity as follows:

• Attack Vector (AV:N): The vulnerable endpoint is network-accessible, enabling remote exploitation.
• Attack Complexity (AC:L): No unusual conditions are required — the attacker simply sends a crafted request.
• Privileges Required (PR:L): The attacker needs only low-level authentication (a role with the get_talos_enrichment capability), not administrative credentials.
• User Interaction (UI:N): No user interaction is required for successful exploitation.
• Scope (S:U): The impact is confined to the vulnerable Splunk instance and does not directly extend to other systems, though token replay may achieve lateral movement.
• Confidentiality, Integrity, Availability (C:H/I:H/A:H): Total compromise of the Splunk instance's data confidentiality, data integrity, and service availability is possible.

Business Impact: Splunk Enterprise Security is a SIEM platform central to the security operations of an organization. A compromise of this system is particularly damaging because it holds or analyzes the organization's security telemetry — alert data, logs, and evidence essential for incident detection and forensics. If an attacker obtains the tokens and gains full access:

1. Loss of visibility: The attacker can delete or modify log data to conceal other malicious activity.
2. Alert suppression: Security monitoring can be disabled or altered, allowing further intrusions to go undetected.
3. Forensic sabotage: Evidence for incident response can be destroyed.
4. Data breach extension: The Splunk instance may hold sensitive log and event data subject to regulatory compliance (e.g., PCI-DSS, HIPAA).

Affected Systems: All deployments of Cisco Talos Intelligence for Splunk Enterprise Security Cloud versions below 1.0.3 within Splunk Enterprise Security 8.0 environments.

Blast Radius: Given that Splunk is often centrally deployed and connected to numerous data sources, the blast radius extends beyond the single Splunk instance — an attacker controlling the Splunk management plane may be able to reach connected data sources, forwarders, or downstream analytics systems the moment those tokens are used against management APIs that have wider access.

EPSS: Not yet scored by FIRST.org; no probability of exploitation data available. CISA KEV: Not listed, indicating no evidence of in-the-wild exploitation as of the most recent catalog update.

Detection Guidance

The following detection content is provided to identify exploitation attempts of CVE-2026-76389. These rules are of a generic nature given the absence of specific endpoint details and should be tuned to the environment.

Sigma Rule

title: Talos Intelligence Enrichment SSRF - Outbound Request to External Host
id: 55b9a13a-3f1f-4c7d-8e96-8fb75e3c267e
status: experimental
description: Detects Splunk instance making outbound HTTP requests from the Talos intelligence enrichment REST API to external/internal hosts - possible SSRF (CVE-2026-76389)
author: valtersit.com Threat Intel
logsource:
  product: splunk
  service: splunkd
  category: webserver
detection:
  selection:
    source: '*Talos*'
    uri_path: '*/services/*/talos*'
    http_method: 'POST'
  filter_legit_destination:
    dest|startswith: '10.'  # adjust to your network bounds
    dest|startswith: '192.168.'
  filter_local_dest:
    dest: '127.0.0.1'
  condition: selection and not filter_legit_destination and not filter_local_dest
level: high
falsepositives:
  - Legitimate enrichment data fetching to Talos cloud service
  - Internal testing or API maintenance
tags:
  - attack.t1190
  - cve.2026.76389
  - cwe.918

YARA Rule

rule CVE_2026_76389_SSRF_TalosPayload {
    meta:
        author = "valtersit.com Threat Intel"
        description = "Detects attacker-crafted request payloads targeting Talos enrichment REST endpoint with external destinations - CVE-2026-76389"
        date = "2026-01-01"
        reference = "https://nvd.nist.gov/vuln/detail/CVE-2026-76389"
        score = 60
    strings:
        $s1 = "get_talos_enrichment" ascii wide nocase
        $s2 = "talos" ascii wide nocase
        $s3 = "http://" ascii wide
        $s4 = "https://" ascii wide
        $s5 = "destination" ascii wide nocase
        $s6 = "enrichment" ascii wide nocase
    condition:
        all of ($s1, $s2) and (any of ($s3, $s4)) and any of ($s5, $s6) and filesize < 10MB
}

Suricata IDS Rule

alert http any any -> any any (msg:"CVE-2026-76389 Possible SSRF via Talos Enrichment REST API"; flow:established,to_server; content:"POST"; http_method; content:"talos"; http_uri; nocase; content:"enrichment"; http_uri; nocase; content:"destination"; http_client_body; nocase; pcre:"/(http|https):\/\/(?!10\.|192\.168\.|172\.(1[6-9]|2[0-9]|3[01])\.|127\.)[^\s\"]+/i"; sid:50076389; rev:1; metadata:attack_target_splunk, cve_2026_76389, created_at_2026_01_01;)

Elastic Detection

sequence by host.name with maxspan=30s
  [ network where event.action == "connection_attempted" and
    source.ip == "127.0.0.1" and
    destination.ip != "127.0.0.1" and
    network.protocol == "http" ]
  [ http where event.category == "web" and
    http.request.method == "POST" and
    url.path contains "talos" and
    http.request.body.text contains "destination" and
    not (destination.ip startsWith "10." or
         destination.ip startsWith "192.168." or
         destination.ip startsWith "172.16." or
         destination.ip startsWith "172.31.") ]

Splunk SPL Query

index=_internal sourcetype=splunkd_web_access OR index=_internal sourcetype=splunkd_access*
  | where like(uri_path, "%talos%") AND like(uri_path, "%enrichment%")
  | rex field=_raw "POST (?P<uri_path>[^ ]*)"
  | search NOT uri_path IN ("/services/data/talos", "/services/config/talos")  // adjust as needed
  | stats count by uri_path, clientip, dest, http_method, _time
  | where count > 1
  | table _time, clientip, uri_path, http_method, dest, count

Wazuh OSSEC Rule

<group name="splunk,">
  <rule id="115270" level="12">
    <decoded_as>json</decoded_as>
    <field name="url" type="pcre2">(?i).*talos.*enrichment.*</field>
    <description>CVE-2026-76389 Possible SSRF via Talos enrichmnet REST API - outbound request to untrusted host</description>
    <group>attack.t1190,cve,ssrf,splunk,</group>
    <mitre>
      <id>T1190</id>
    </mitre>
    <options>no_full_log</options>
  </rule>
</group>

Mitigation & Patch Guidance

Patch Confidence: 0/4 — No patch evidence from any tracked source. The vulnerability is considered UNPATCHED at the time of writing. No vendor fix, advisory, or version release (beyond the implied 1.0.3 threshold) has been verified. No workarounds have been published by the vendor.

1. Immediate Mitigations (until vendor patch is available):

• Least privilege enforcement: Audit all existing roles in Splunk Enterprise Security Cloud. Restrict the get_talos_enrichment capability to only the smallest necessary set of user accounts. Where possible, disable the capability for standard users pending patch deployment.
• Network egress filtering: Configure firewall or proxy rules on the Splunk instance to deny outbound HTTP/HTTPS connections to unknown or non-approved external hosts. Allow outbound connections only to legitimate Talos intelligence cloud IP ranges and known update endpoints.
• Token hygiene: Rotate any tokens or service credentials that the Talos enrichment endpoint uses for Splunk management requests. This limits the residual damage if tokens have already been exfiltrated.
• Monitoring: Deploy the detection rules provided above to identify anomalous outbound connections from the Splunk instance, especially those initiated from the Talos enrichment REST API handler.

2. Patch / Upgrade Steps:

• Monitor vendor channels: Check the Splunk Enterprise Security documentation and Cisco Talos release notes regularly for a patched version (expected to be 1.0.3 or later) or a vendor security advisory.
• Upgrade when available: Once a patched version is released, upgrade the Talos Intelligence add-on to the latest version. Validate that the upgrade preserves existing enrichment configurations and does not break other add-ons.
• Rollback plan: Document a rollback plan in case the patched version introduces regressions.

3. Long-Term Hardening:

• Harden REST API access: Limit access to the Splunk management API to trusted network segments using network access control lists. Restrict the API bind address and use TLS client certificates where feasible.
• Incident response prep: Prepare IR playbooks for token theft that include immediate token revocation, audit of management API access logs, and forensic preservation of the Splunk instance.
• Input validation: Contact the vendor and request that they implement destination allow-listing for all Splunk management requests, ensuring the destination is resolved only from server-side configuration.
• Security awareness: Train SOC analysts to recognize that their Splunk roles may carry the get_talos_enrichment capability and to report any unusual enrichment behavior.

Threat Actor Activity: No threat actor campaigns, exploit-in-the-wild evidence, or CISA KEV entry exists for this CVE. The attack has not been observed in active exploitation.

References

1. NVD Entry — CVE-2026-76389: https://nvd.nist.gov/vuln/detail/CVE-2026-76389
2. Splunk Documentation — Deploy Cisco Talos Intelligence for Splunk Enterprise Security: https://help.splunk.com/en/splunk-enterprise-security-8/user-guide/8.0/introduction/deploy-cisco-talos-intelligence-for-splunk-enterprise-security-cloud-only
3. Cisco Talos Intelligence Group — Product Page: https://talosintelligence.com/
4. MITRE ATT&CK — T1190 Exploit Public-Facing Application: https://attack.mitre.org/techniques/T1190/
5. CWE-918 Server-Side Request Forgery: https://cwe.mitre.org/data/definitions/918.html