CVE-2026-76276

Executive Summary

CVE-2026-76276 is a low-severity information disclosure vulnerability in Splunk Enterprise in which a low-privileged authenticated user (without the "admin" or "power" roles) can retrieve the original JavaScript source code of the Discover Splunk Observability Cloud app through Splunk Web. The flaw stems from production JavaScript bundles that contain embedded source maps, which expose unminified original source code. Impact is limited to confidentiality of application source code (CVSS 4.3), with no integrity or availability impact.

Technical Analysis

The vulnerability is classified as CWE-1188 (Insecure Default Initialization of Resource) — specifically, the default packaging of production JavaScript bundles with embedded source maps. Source maps are metadata files that map minified/transpiled code back to its original authoring form, typically for debugging. When shipped inside a production bundle, they allow any client that can load the bundle to recover the original, readable source — including comments, internal logic, and potentially sensitive strings or endpoints.

The attack surface is Splunk Web, the browser-facing management/search UI. The affected component is the Discover Splunk Observability Cloud app, whose production JavaScript bundles contain embedded source maps that include original source code. Because the resource is served through Splunk Web, any authenticated user session that can reach the app's static assets can request them.

Access control is the crux: the NVD description states a low-privileged user "that does not hold the 'admin' or 'power' Splunk roles" can retrieve the source. This indicates the static assets (or the source-map content) are reachable via the standard Splunk Web role-based access model without elevated privileges. The affected versions are Splunk Enterprise below 10.4.3, 10.2.7, and 10.0.10. Notably, Splunk Enterprise 9.4.x is explicitly not affected, indicating the vulnerable app packaging was introduced in the 10.x line.

No public PoC, exploit code, or Nuclei template exists. The CVSS vector (AV:N/AC:L/PR:L/UI:N/S:U/C:L/I:N/A:N) confirms: network-reachable, low attack complexity, requires low privileges (authenticated), no user interaction, unchanged scope, and low confidentiality-only impact. EPSS is 0.00176 (6.6th percentile), indicating very low predicted exploitation likelihood.

Exploitation Scenarios

No public PoC is available; the attack chain is inferred from the vulnerability class (exposed source maps) and the NVD description.

1. Reconnaissance / Target Identification. An attacker with at least a low-privileged authenticated account enumerates a Splunk Enterprise instance (versions < 10.4.3, < 10.2.7, or < 10.0.10, excluding 9.4.x). The attacker identifies Splunk Web and the Discover Splunk Observability Cloud app as installed.

2. Triggering the Flaw Class. The attacker requests the app's production JavaScript bundles through Splunk Web. Because those bundles contain embedded source maps that include original source code, the client can recover the original, unminified source — no elevated ("admin"/"power") role is required, since the assets are reachable under the standard role-based access model.

3. Payload / Execution Method. This is a passive disclosure class: the "payload" is simply the retrieval of static bundle assets and the extraction of embedded source-map data client-side. No code injection, memory corruption, or server-side command execution is involved.

4. Post-Exploitation Impact. The attacker obtains the original source of the Discover Splunk Observability Cloud app. This can aid further reconnaissance — revealing internal logic, structure, or embedded strings useful for planning subsequent attacks. There is no direct integrity or availability impact, and no evidence of exploit-in-the-wild activity.

No public PoC available; attack chain is inferred from vulnerability class.

Impact Assessment

The CVSS 3.1 base score is 4.3 (Medium), vector CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:L/I:N/A:N. Subscore interpretation:

• AV:N (Network) — exploitable over the network via Splunk Web.
• AC:L (Low) — no special conditions beyond normal access.
• PR:L (Low Privileges) — requires a valid low-privileged authenticated account; neither "admin" nor "power" roles needed.
• UI:N (No User Interaction) — no victim action required.
• S:U (Unchanged) — impact confined to the vulnerable component.
• C:L (Low Confidentiality) — disclosure limited to application source code, not credentials, customer data, or the search index.
• I:N / A:N — no integrity or availability impact.

Blast radius: Any Splunk Enterprise 10.x deployment below the fixed patch levels (excluding 9.4.x) that has the Discover Splunk Observability Cloud app installed and permits low-privileged user access to Splunk Web. Business impact is primarily intellectual-property and reconnaissance exposure: leaked source can lower the cost of follow-on attacks and reveal implementation detail, but this CVE alone does not grant data access, privilege escalation, or service disruption. The low EPSS (0.00176) and absence of any KEV listing or public exploit reflect limited near-term risk.

Detection Guidance

Sigma Rule

title: Splunk Observability Cloud App Source Map Retrieval
id: 8f3c1a2e-7627-4c76-9a01-splunk76276
status: experimental
description: Detects retrieval of Splunk Observability Cloud app JavaScript bundles/source maps by low-privileged users via Splunk Web.
references:
  - https://nvd.nist.gov/vuln/detail/CVE-2026-76276
author: Threat Intelligence
logsource:
  category: webserver
  product: splunk
detection:
  selection_path:
    cs-uri-stem|contains:
      - '.js.map'
      - 'observability'
  selection_app:
    cs-uri-stem|contains: 'splunk_observability_cloud'
  selection_status:
    sc-status: 200
  condition: (selection_path or selection_app) and selection_status
falsepositives:
  - Legitimate developer debugging via browser devtools
level: low
tags:
  - attack.t1213
  - cve.2026-76276

YARA Rule

rule CVE_2026_76276_Splunk_SourceMap_Leak
{
    meta:
        description = "Detects embedded source maps exposing original source in Splunk Observability Cloud app JS bundles"
        reference = "https://nvd.nist.gov/vuln/detail/CVE-2026-76276"
        cve = "CVE-2026-76276"
        cwe = "CWE-1188"
        author = "Threat Intelligence"
        date = "2026-01-01"
    strings:
        $sm1 = "sourceMappingURL=" ascii
        $sm2 = "//# sourceMappingURL=data:application/json" ascii
        $obs1 = "observability" ascii nocase
        $app = "splunk_observability_cloud" ascii nocase
    condition:
        ($sm1 or $sm2) and ($obs1 or $app)
}

Suricata IDS Rule

alert http any any -> any any (msg:"CVE-2026-76276 Splunk Observability Cloud Source Map Retrieval"; flow:established,to_server; http.method; content:"GET"; http.uri; content:"observability"; http.uri; content:".js"; http.uri; content:"sourceMappingURL"; http.user_agent; content:"Mozilla"; classtype:attempted-recon; reference:cve,2026-76276; reference:url,nvd.nist.gov/vuln/detail/CVE-2026-76276; sid:202676276; rev:1;)

Elastic Detection

sequence by user.name with maxspan=2m
  [ network where http.request.method == "GET" and stringContains(http.request.path, ".js.map") ]
  [ network where http.request.method == "GET" and stringContains(http.request.path, "observability") ]

Splunk SPL Query

index=web OR index=proxy sourcetype=access_common OR sourcetype=access_combined
| search (uri_path="*observability*" AND uri_path="*.js*") OR uri_path="*.js.map" OR uri_path="*sourceMappingURL*"
| stats count values(status) AS status vals by src_ip, uri_path, user
| where status=200
| sort - count

Wazuh OSSEC Rule

<group name="splunk,web,">
  <rule id="100276" level="6">
    <if_sid>31100</if_sid>
    <id>^311</id>
    <url>observability</url>
    <description>CVE-2026-76276: Possible Splunk Observability Cloud app source map retrieval via Splunk Web</description>
    <mitre>
      <id>T1213</id>
    </mitre>
    <group>recon,cve_2026_76276,</group>
  </rule>
</group>

Mitigation & Patch Guidance

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

1. Immediate mitigations (no vendor-confirmed workaround available):

   • Restrict the affected app: remove or disable the Discover Splunk Observability Cloud app from Splunk Web where it is not operationally required.
   • Enforce least privilege for Splunk roles, limiting which low-privileged users can reach Splunk Web and the app.
   • Restrict network access to Splunk Web via firewall/ACLs to trusted management networks.
   • Inspect and, where feasible at the reverse-proxy layer, block access to exposed .js.map source-map assets while validating no break in app functionality (test before enforcement).

2. Patch / upgrade steps: Per the NVD description, upgrade to Splunk Enterprise 10.4.3, 10.2.7, or 10.0.10 or later. Track the official Splunk security advisory (SVD) for confirmation and fixed-build details; no patch source was confirmed in the tracked data.

3. Long-term hardening:

   • Adopt a secure build pipeline that strips source maps and debugging metadata from production JavaScript bundles before release.
   • Include exposed-source-map and source-code-disclosure checks in CI/CD and release QA.
   • Maintain asset inventory to quickly assess exposure when app-packaging flaws surface.
   • Monitor web access logs for anomalous retrieval of app static assets and source maps.

References

• NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-76276
• Splunk Documentation — About configuring role-based user access: https://help.splunk.com/en/splunk-enterprise/administer/manage-users-and-security/10.4/manage-splunk-platform-users-and-roles/about-configuring-role-based-user-access
• Splunk Documentation — Splunk Observability Cloud previews: https://help.splunk.com/en/splunk-enterprise/search/search-manual/10.4/observability/splunk-observability-cloud-previews
• Splunk Documentation — Navigating Splunk Web: https://help.splunk.com/en/splunk-enterprise/search/search-tutorial/10.4/part-1-getting-started/navigating-splunk-web
• CWE-1188 — Insecure Default Initialization of Resource: https://cwe.mitre.org/data/definitions/1188.html

No CISA KEV listing exists for this CVE. No public PoC, exploit code, or Nuclei template is available, and no threat actor campaign or exploit-in-the-wild evidence has been observed.