CVE-2026-76272

Executive Summary

CVE-2026-76272 is a missing authorization check (CWE-862) in Splunk Secure Gateway, a component of Splunk Enterprise, that allows a low-privileged authenticated user—one who does not hold the "admin" or "power" Splunk roles—to cause the gateway to sign attacker-controlled payloads. The flaw affects Splunk Enterprise versions below 10.4.3, 10.2.7, 10.0.10, and 9.4.15, and Splunk Secure Gateway versions below 3.10.11, 3.9.25, and 3.8.72. While the CVSS score is moderate (4.3, reflecting limited integrity impact), the ability to obtain valid gateway signatures over attacker-supplied content may undermine trust assumptions in downstream consumers that rely on signature validity as an authorization or trust signal.

Technical Analysis

The vulnerability class is CWE-862: Missing Authorization. The NVD description states that Splunk Secure Gateway "does not verify that the user is authorized to request a signature." As a result, an authenticated user lacking the "admin" or "power" roles can invoke the gateway's signing capability and cause it to produce a signature over "attacker-controlled payloads."

The relevant attack surface is the Splunk Secure Gateway signing functionality exposed to authenticated platform users. The precise request parameters, endpoints, and the signature scheme are not enumerated in the available intelligence, and no public PoC or exploit code exists. Accordingly, this analysis stays at the vulnerability-class level rather than fabricating implementation specifics.

Analogous to an unauthenticated-signing-oracle pattern, the core defect is a missing capability/role check on the signing operation. Splunk's role model is built on capabilities; the reference documentation cited by the vendor ("Define roles on the Splunk platform with capabilities") governs which roles may exercise sensitive functions. The gateway should have gated the signing request behind a capability restricted to trusted roles, but it did not.

The CVSS vector CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:L/A:N indicates:

• AV:N — remotely reachable over the network.
• AC:L — no special attack conditions.
• PR:L — the attacker must be authenticated with low privileges.
• UI:N — no user interaction required.
• C:N — no confidentiality impact.
• I:L — limited integrity impact (signatures produced over attacker content).
• A:N — no availability impact.

The limited integrity score reflects that the flaw does not directly grant code execution or data disclosure; its danger is in the trust conferred by a legitimate cryptographic signature.

Exploitation Scenarios

No public PoC is available; the attack chain below is inferred from the vulnerability class (missing authorization) and the NVD description.

1. Reconnaissance / target identification. The attacker identifies a Splunk Enterprise deployment running an affected version and confirms the possible presence of Splunk Secure Gateway (affected versions below 3.10.11, 3.9.25, 3.8.72). Public Shodan dorks for Splunk web interfaces (port 8000, "Splunk" in title/HTML) assist in locating exposed instances.

2. Authentication with low-privileged account. The attacker obtains or already holds valid Splunk credentials for a user that does NOT possess the "admin" or "power" roles. Because PR:L is required, this account is the entry primitive.

3. Triggering the missing authorization flaw. The authenticated low-privileged user submits a request to Splunk Secure Gateway to sign a payload they control. Because the gateway fails to verify that the user is authorized to request a signature, the signing request is processed rather than rejected. The attacker does not need admin or power capabilities to do this.

4. Payload/execution at class level. The gateway returns a signature over the attacker-controlled content. The attacker now possesses a validly signed payload originating from the trusted Splunk Secure Gateway component.

5. Post-exploitation impact. The attacker uses the signed payload to impersonate trusted-content origin, to bypass downstream trust checks that treat a valid Splunk Secure Gateway signature as proof of authorization or integrity, or to poison any consumer (mobile app, backend service, or integration) that trusts gateway-signed data. Confidentiality and availability remain unaffected (C:N, A:N); the impact is confined to limited integrity (I:L).

Impact Assessment

• Confidentiality: None (C:N).
• Integrity: Low (I:L). The core impact is the production of trusted signatures over untrusted content, enabling spoofing or manipulation of downstream trust decisions.
• Availability: None (A:N).
• Scope: Unchanged (S:U) — the vulnerable component and impacted component are the same.
• Attack vector: Network (AV:N), Low complexity (AC:L), Low privileges (PR:L), No user interaction (UI:N).

Business impact. Any environment where Splunk Secure Gateway-signed payloads are consumed as a trust anchor is at risk. Downstream mobile or integration components that assume a valid signature implies authorization may act on attacker-supplied data. The blast radius is bounded by the trust model surrounding the gateway signatures, not by Splunk Enterprise itself. Because exploitation requires authenticated access (PR:L), external attackers must first obtain low-privileged credentials; malicious insiders or compromised low-privileged accounts are the most likely actors. CISA KEV status is NO, EPSS is 0.00168 (5.6th percentile), and no exploit code exists publicly, indicating low current exploitation pressure.

Detection Guidance

Sigma Rule

title: Splunk Secure Gateway Unauthorized Signing Request (CVE-2026-76272)
id: 8f2c1a44-7d3e-4b9a-9c1e-202676272001
status: experimental
description: Detects low-privileged Splunk users invoking Secure Gateway signing without admin or power role.
references:
  - https://nvd.nist.gov/vuln/detail/CVE-2026-76272
author: valtersit.com
date: 2026/01/01
logsource:
  product: splunk
  service: secure_gateway
detection:
  selection_action:
    action|contains:
      - 'secure_gateway'
      - 'sign'
      - 'signing'
  selection_user:
    user_role:
      - 'user'
      - 'guest'
      - 'analyst'
  filter_privileged:
    user_role:
      - 'admin'
      - 'power'
  condition: selection_action and selection_user and not filter_privileged
falsepositives:
  - Legitimate service accounts not mapped to admin/power but intended to sign
level: medium
tags:
  - attack.t1078
  - cve.2026.76272

YARA Rule

rule CVE_2026_76272_Splunk_Secure_Gateway_Signing
{
    meta:
        description = "Detects Splunk Secure Gateway signing-related strings tied to CVE-2026-76272"
        author = "valtersit.com"
        reference = "https://nvd.nist.gov/vuln/detail/CVE-2026-76272"
        date = "2026-01-01"
        severity = "medium"
    strings:
        $gw1 = "Splunk Secure Gateway" ascii wide nocase
        $gw2 = "secure_gateway" ascii wide nocase
        $sign1 = "sign" ascii wide
        $sign2 = "signature" ascii wide
        $ver1 = "10.4.3" ascii wide
        $ver2 = "10.2.7" ascii wide
        $ver3 = "9.4.15" ascii wide
    condition:
        (uint16(0) == 0x5A4D or uint32(0) == 0x464C457F) and
        ($gw1 or $gw2) and ($sign1 or $sign2)
}

Suricata IDS Rule

alert http any any -> any any (msg:"CVE-2026-76272 Splunk Secure Gateway Unauthorized Signing Attempt"; flow:established,to_server; http.method; content:"POST"; http.uri; content:"secure_gateway"; nocase; http.uri; content:"sign"; nocase; sid:2026762720; rev:1; reference:cve,2026-76272; classtype:attempted-user; metadata:created_at 2026_01_01, updated_at 2026_01_01;)

Elastic Detection

sequence by user.name with maxspan=5m
  [authentication where event.outcome == "success"]
  [http where url.path : "*secure_gateway*" and url.path : "*sign*" and
   not (user.roles : "admin" or user.roles : "power")]

Splunk SPL Query

index=_audit action IN ("secure_gateway*", "*sign*")
| where NOT match('roles', "(?i)admin|power")
| stats count min(_time) as firstTime max(_time) as lastTime values(roles) as roles by user action src_ip
| where count > 0
| convert ctime(firstTime) ctime(lastTime)

Wazuh OSSEC Rule

<group name="splunk,cve-2026-76272,">
  <rule id="202676" level="7">
    <decoded_as>json</decoded_as>
    <field name="action">secure_gateway.*sign</field>
    <field name="roles" negate="yes">admin|power</field>
    <description>CVE-2026-76272: Low-privileged user requested Splunk Secure Gateway signature</description>
    <mitre>
      <id>T1078</id>
    </mitre>
    <group>unauthorized_action,</group>
  </rule>
</group>

Mitigation & Patch Guidance

Patch confidence: 0/4 (UNPATCHED — no patch evidence from any tracked source). Note: the NVD description enumerates fixed versions (Splunk Enterprise 10.4.3, 10.2.7, 10.0.10, 9.4.15; Splunk Secure Gateway 3.10.11, 3.9.25, 3.8.72), which should be treated as the authoritative remediation targets even though no vendor patch artifact was confirmed by tracked sources.

1. Immediate mitigations

   • Restrict Splunk Secure Gateway signing capability to trusted roles only. Review role definitions and ensure no non-admin/non-power role is granted signing rights.
   • Apply least privilege to all authenticatable accounts; audit for over-provisioned low-privileged users.
   • Reduce external exposure of Splunk Enterprise (port 8000 and gateway interfaces) via network ACLs/firewalls.
   • Monitor audit logs for signing requests originating from users lacking admin/power roles.

2. Patch / upgrade steps

   • Upgrade Splunk Enterprise to 10.4.3, 10.2.7, 10.0.10, or 9.4.15 (as applicable to your branch) and Splunk Secure Gateway to 3.10.11, 3.9.25, or 3.8.72.
   • Re-validate role/capability assignments after upgrade.
   • Confirm fixed component versions in the Splunk UI and via package inventory.

3. Long-term hardening

   • Implement capability-based authorization review cycles for all signing/trust operations.
   • Enforce MFA on all Splunk accounts to reduce risk from low-privileged credential compromise (PR:L).
   • Adopt a zero-trust posture for signature consumers: do not treat signature validity alone as authorization proof.
   • Continuously monitor CVE/EPSS feeds for updated exploitation evidence.

References

• NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-76272
• Splunk Documentation — Define roles on the Splunk platform with capabilities: https://help.splunk.com/en/splunk-enterprise/administer/manage-users-and-security/10.2/manage-splunk-platform-users-and-roles/define-roles-on-the-splunk-platform-with-capabilities
• CWE-862 Missing Authorization: https://cwe.mitre.org/data/definitions/862.html
• FIRST EPSS (score 0.00168, 5.6th percentile): https://www.first.org/epss/
• CISA Known Exploited Vulnerabilities Catalog (CVE not listed): https://www.cisa.gov/known-exploited-vulnerabilities-catalog

No known threat actor campaigns or exploit-in-the-wild evidence was identified in the provided intelligence (CISA KEV: NO; PoC: None; Exploit Code: None; Nuclei Template: NO).