CVE-2026-76281

Executive Summary

CVE-2026-76281 is an improper access control vulnerability (CWE-284) in Splunk Enterprise, disclosed as part of a batch of internally identified issues that Splunk resolved in versions 10.4.3, 10.2.7, 10.0.10, and 9.4.15. The vulnerability carries a CVSS 3.1 base score of 5.3 (Medium), reflecting a network-reachable flaw requiring no privileges and no user interaction, with a limited confidentiality impact and no integrity or availability impact. Splunk Enterprise deployments that log, index, and expose security telemetry — including SIEM, SOC, and IT operations platforms — are the affected class of systems, making even a low-severity access control gap operationally relevant because the data at rest in these platforms is itself highly sensitive.

Technical Analysis

CVE-2026-76281 is classified under CWE-284, Improper Access Control. This weakness family covers cases where an application fails to correctly enforce authorization decisions — for example, where a resource or operation can be reached through a path that bypasses the intended permission check, where an access decision is made on attacker-controllable or incorrect input, or where a role/permission boundary is applied inconsistently across interfaces. The NVD description does not enumerate the specific component, endpoint, API path, or parameter involved, and the CNA title field is empty. Accordingly, this report describes the vulnerability strictly at the class level and does not attribute behavior to specific Splunk modules or interfaces.

What the data does establish:

• Vulnerability class: Improper access control (CWE-284). This is an authorization/access-decision defect, not a memory-safety, injection, or deserialization issue.
• Attack vector: Network (AV:N). The flaw is reachable over the network, consistent with Splunk Enterprise's web and REST service surfaces.
• Complexity: Low (AC:L). No specialized conditions, race timing, or unusual preconditions are required.
• Privileges required: None (PR:N). An unauthenticated or trivially positioned attacker can trigger the condition.
• User interaction: None (UI:N). No victim action is needed.
• Impact: Confidentiality Low (C:L), Integrity None (I:N), Availability None (A:N). The effect is limited unauthorized information disclosure — not modification of data, not denial of service, not code execution.

The combination of PR:N, UI:N, and AV:N with only C:L is characteristic of an access control weakness that exposes a constrained set of information — for example, a resource that leaks metadata or a subset of records — rather than a full database compromise. The CVSS scope is Unchanged (S:U), meaning the vulnerable component and the impacted component are the same security authority; exploitation does not pivot the attacker into a different trust domain by virtue of the flaw itself.

Splunk's description states the issues were internally identified and that multiple vulnerabilities were grouped by CWE with one CVE identifier assigned per group. This is an important analytic point: the CVE identifier covers a class of access control issues rather than a single discrete code path. As a result, the practical attack surface may span more than one interface, and defenders should not assume a single-endpoint fix. It also means that the absence of a public CNA description and the empty title are expected artifacts of grouped disclosure, not an anomaly.

Because no affected version ranges were enumerated in the supplied data, the precise vulnerable-to-fixed boundaries for each branch cannot be stated beyond the fixed versions named. Treated as fixed-release markers, the branches are Splunk Enterprise 9.4.x (fixed in 9.4.15), 10.0.x (fixed in 10.0.10), 10.2.x (fixed in 10.2.7), and 10.4.x (fixed in 10.4.3). Deployments at or below the prior maintenance release on each branch should be presumed affected until verified against Splunk's own advisory.

Exploitation Scenarios

No public proof-of-concept, exploit code, or Nuclei template exists for CVE-2026-76281 as of this writing. The attack chain below is therefore inferred from the vulnerability class (CWE-284) and the CVSS metric set, and deliberately avoids asserting specific implementation details that are not present in the source data.

1. Reconnaissance and target identification. An attacker identifies internet- or intranet-reachable Splunk Enterprise instances using standard service fingerprinting. Splunk's web interface and management/REST service are the natural candidates, since the CVSS vector establishes network reachability with no authentication. Shodan and similar internet-wide scanners can enumerate exposed instances via product and title fingerprints.

2. Triggering the access control flaw. Given PR:N and UI:N, the attacker issues a network request — directly, without authenticating — to a resource that should require authentication or an elevated role. The defining characteristic of an improper access control flaw is that the authorization check is absent, misapplied, or evaluated on the wrong subject, so the request is served rather than rejected. Because the CVE groups multiple internally identified issues by CWE, more than one request pattern may satisfy the condition. The specific endpoint, method, and parameter required are not disclosed and are not fabricated here.

3. Payload and execution. CWE-284 exploitation typically requires no malicious payload in the injection sense; the "payload" is the crafted request itself, constructed to reach a code path where the access decision is not enforced. There is no memory corruption, no injection string, and no shellcode implied by the stated weakness class or by the I:N/A:N impact profile. An attacker who can reach the vulnerable interface can attempt the request directly.

4. Post-exploitation impact. Success yields unauthorized read access to information the attacker is not entitled to — consistent with C:L. This is information disclosure, not lateral movement, not persistence, and not code execution. In a Splunk context, even limited disclosure can be consequential, because indexed data frequently includes authentication logs, network telemetry, application traces, and potentially credentials or tokens captured in log streams. An attacker who obtains a partial view of such data can refine later, more targeted operations, or use the disclosed content for credential harvesting and internal reconnaissance. No integrity or availability effects are expected from this CVE alone.

Defenders should note the absence of a public exploit and the very low EPSS score (0.00147, ~3.4th percentile) as signals that mass exploitation is unlikely in the near term. This does not eliminate risk: the low complexity (AC:L), zero-privilege (PR:N), zero-interaction (UI:N) profile means that once a technique is known or discovered, it is inexpensive to attempt at scale.

Impact Assessment

The CVSS 3.1 base score of 5.3 places CVE-2026-76281 in the Medium severity band. Decomposed:

• AV:N (Network) — the flaw is exploitable remotely, which raises exposure for any Splunk Enterprise instance reachable from untrusted networks.
• AC:L (Low complexity) — no unusual conditions are needed; repeatable requests suffice.
• PR:N (No privileges) — no account, credential, or prior foothold is required, removing the most common practical barrier to exploitation.
• UI:N (No interaction) — no administrator or user must be induced to act, enabling fully automated attempts.
• S:U (Unchanged) — impact is confined to the vulnerable component's own security authority.
• C:L / I:N / A:N — limited confidentiality loss only; no modification of data and no disruption of service.

Business impact. Splunk Enterprise is core security infrastructure. It aggregates and indexes log and event data from across an estate, including authentication records, endpoint telemetry, network flows, and application output. Unauthorized read access to a subset of that data can: (a) reveal defensive posture and detection coverage to an adversary, enabling evasion; (b) expose credentials, API keys, session tokens, or PII that were inadvertently logged; and (c) furnish internal hostnames, service topology, and user identity information for follow-on targeting. Because the integrity and availability impacts are None, this CVE will not take monitoring offline or corrupt indexed data — the risk is disclosure-driven.

Blast radius. Bounded by the reachability of the affected interface and by the sensitivity of the specific information the access control gap exposes. The grouped nature of the disclosure means the exposed data set may be defined per issue rather than uniformly. Defenders should treat the blast radius as "whatever Splunk Enterprise can be made to return to an unauthorized requester through the vulnerable interface(s)" and scope accordingly.

Likelihood. EPSS 0.00147 (approximately the 3.4th percentile of all scored CVEs), no CISA KEV listing, no public PoC, no exploit code, and no Nuclei template currently exist. Short-term exploitation likelihood is low. Priority should be driven by exposure — internet-facing Splunk Enterprise is a materially higher risk than an air-gapped internal deployment.

Detection Guidance

Detection content below is written to the vulnerability class (improper access control / unauthenticated access to protected Splunk resources) and to the affected product, because no specific endpoint or parameter is disclosed. Rules are intentionally behavioral and should be tuned to the environment to avoid false positives from legitimate service accounts and health checks.

Sigma Rule

title: Potential Splunk Enterprise Improper Access Control Exploitation (CVE-2026-76281)
id: 9f1c4b2e-7a63-4d18-9c05-3e6b8a2f4d71
status: experimental
description: Detects repeated unauthenticated or low-privilege access attempts against Splunk Enterprise web/REST resources that return successful responses, consistent with CWE-284 improper access control exploitation.
references:
  - https://nvd.nist.gov/vuln/detail/CVE-2026-76281
author: valtersit.com
date: 2026/01/01
tags:
  - attack.t1190
  - cve.2026.76281
logsource:
  category: webserver
  product: splunk
detection:
  selection_status:
    sc-status:
      - 200
      - 201
  selection_paths:
    cs-uri-stem|contains:
      - '/services/'
      - '/en-US/'
      - '/api/'
  filter_authenticated:
    cs-username|exists: true
  filter_healthcheck:
    cs-user-agent|contains:
      - 'Splunk-Monitoring'
      - 'HealthCheck'
  condition: selection_status and selection_paths and not filter_authenticated and not filter_healthcheck
  timeframe: 5m
fields:
  - c-ip
  - cs-method
  - cs-uri-stem
  - cs-uri-query
  - cs-user-agent
  - sc-status
falsepositives:
  - Unauthenticated health or readiness probes from load balancers
  - Legitimate public-facing endpoints configured by the administrator
level: medium

YARA Rule

rule CVE_2026_76281_Splunk_AccessControl_Probe
{
    meta:
        description = "Detects HTTP request artifacts targeting Splunk Enterprise service paths without authentication context, consistent with CWE-284 improper access control probing (CVE-2026-76281)"
        author = "valtersit.com"
        reference = "https://nvd.nist.gov/vuln/detail/CVE-2026-76281"
        date = "2026-01-01"
        severity = "medium"

    strings:
        $svc   = "/services/" ascii nocase
        $api   = "/api/" ascii nocase
        $enus  = "/en-US/" ascii nocase
        $req1  = "GET " ascii
        $req2  = "POST " ascii
        $splunk = "Splunk" ascii nocase
        $ua1   = "curl" ascii nocase
        $ua2   = "python" ascii nocase

    condition:
        uint16(0) == 0x4854 and
        ($req1 or $req2) and
        ($svc or $api or $enus) and
        $splunk and
        ($ua1 or $ua2)
}

Suricata IDS Rule

alert http any any -> any any (msg:"CVE-2026-76281 Splunk Enterprise Improper Access Control Probe"; flow:established,to_server; http.method; content:"GET"; http.uri; content:"/services/"; nocase; http.user_agent; content:"curl"; nocase; threshold:type both, track by_src, count 20, seconds 60; classtype:attempted-recon; reference:cve,2026-76281; reference:url,nvd.nist.gov/vuln/detail/CVE-2026-76281; sid:202676281; rev:1;)

Elastic Detection

sequence by source.ip with maxspan=60s
  [ network where
      network.protocol == "http" and
      http.request.method in ("GET", "POST") and
      (http.request.uri : "/services/*" or http.request.uri : "/api/*" or http.request.uri : "/en-US/*") and
      not http.request.headers.authorization : "*" ]
  [ network where
      network.protocol == "http" and
      http.response.status_code in (200, 201) and
      (http.request.uri : "/services/*" or http.request.uri : "/api/*" or http.request.uri : "/en-US/*") ]

Splunk SPL Query

index=web OR index=splunk_web OR index=proxy
  (uri_path="/services/*" OR uri_path="/api/*" OR uri_path="/en-US/*")
  status IN (200, 201)
  NOT (user=* OR authorization=* OR cookie=*)
| eval src=coalesce(src_ip, clientip, c_ip)
| bin _time span=1m
| stats count AS attempts dc(uri_path) AS unique_paths values(uri_path) AS paths BY src _time
| where attempts >= 10
| sort - attempts

Wazuh OSSEC Rule

<group name="web,splunk,cve-2026-76281,">
  <rule id="202676281" level="7">
    <decoded_as>web-accesslog</decoded_as>
    <field name="url">/services/|/api/|/en-US/</field>
    <regex>\"(GET|POST) .*(/services/|/api/|/en-US/).*\" (200|201) </regex>
    <description>CVE-2026-76281: Possible unauthenticated access control bypass against Splunk Enterprise service endpoint</description>
    <mitre>
      <id>T1190</id>
    </mitre>
    <group>attack,</group>
  </rule>

  <rule id="202676282" level="10" frequency="20" timeframe="60">
    <if_matched_sid>202676281</if_matched_sid>
    <same_source_ip />
    <description>CVE-2026-76281: Repeated unauthenticated Splunk Enterprise service access from same source - probable automated access control probing</description>
    <mitre>
      <id>T1190</id>
    </mitre>
    <group>attack,</group>
  </rule>
</group>

Mitigation & Patch Guidance

Patch confidence: 0/4 — UNPATCHED per tracked sources. No vendor fix URL, no OSV package mapping, no affected-version enumeration, and no workaround guidance were supplied in the CVE data. The version list below is drawn from the NVD description's statement of releases in which Splunk addressed the issue; it is not corroborated by a tracked patch source in this dataset and should be verified directly against Splunk's own advisory before being relied upon.

1. Immediate mitigations (while verification is pending):

• Remove Splunk Enterprise management and web interfaces from untrusted network exposure. Restrict the web UI, REST API, and management port to trusted administrative networks via firewall rules, security groups, or reverse-proxy allow-lists.
• Enforce authentication at the perimeter. Where a reverse proxy or load balancer fronts Splunk, require authentication before forwarding requests to service paths, so that unauthenticated requests never reach the application.
• Apply least privilege to the Splunk service account and restrict role assignments to the minimum required; audit for roles or capabilities that grant broader access than operationally necessary.
• Enable and centralize Splunk's own audit logging, and forward those logs to a separate, independently monitored platform so that access control events cannot be suppressed by an attacker operating within the same instance.
• Monitor for the behavioral patterns in the Detection Guidance section above — successful responses to requests lacking authentication context against service paths.

2. Patch / upgrade steps:

• Confirm the deployed Splunk Enterprise version and branch (splunk version).
• Upgrade to the fixed release on the applicable branch: 9.4.15, 10.0.10, 10.2.7, or 10.4.3.
• Consult Splunk's official security advisory for CVE-2026-76281 for the authoritative affected-version matrix and any prerequisite upgrade paths between maintenance releases. Because the CVE groups multiple issues by CWE, confirm that the target release closes the entire group, not just one issue.
• Validate post-upgrade that previously reachable unauthorized paths now return authorization failures.
• Restage and re-verify detection content after upgrade, since response codes and paths for the fixed interfaces may change.

3. Long-term hardening:

• Treat Splunk Enterprise as a tier-0 security asset: network-isolate it, place it behind authenticated access control, and include it in privileged access management.
• Establish a recurring patch cadence tied to Splunk security advisories, with defined SLAs for Medium-severity authorization flaws on externally reachable instances.
• Perform periodic authorization testing — specifically unauthenticated and low-privilege access attempts — against service paths to catch access control regressions before adversaries do.
• Sanitize data before indexing: scrub credentials, tokens, and secrets at ingest so that even a confidentiality-limited disclosure cannot yield authentication material.
• Maintain asset inventory and exposure monitoring to detect newly internet-facing Splunk instances, since reachability is the primary driver of risk for this CVE.

References

• NVD — CVE-2026-76281: https://nvd.nist.gov/vuln/detail/CVE-2026-76281
• CWE-284: Improper Access Control — https://cwe.mitre.org/data/definitions/284.html
• Splunk Security Advisories (authoritative vendor advisory portal for the affected versions and per-CVE detail): https://advisory.splunk.com/
• FIRST EPSS — CVE-2026-76281 score lookup: https://api.first.org/data/v1/epss?cve=CVE-2026-76281
• MITRE ATT&CK T1190 — Exploit Public-Facing Application: https://attack.mitre.org/techniques/T1190/

Exploit-in-the-wild and threat actor status: No known threat actor campaigns, no exploit-in-the-wild evidence, no CISA KEV listing, no public proof-of-concept, and no Nuclei template were identified for CVE-2026-76281 in the supplied data. EPSS is 0.00147 (approximately the 3.4th percentile). Splunk characterized the underlying issues as internally identified, which typically correlates with a lower probability of immediate public weaponization.