CVE-2026-67103

Executive Summary

CVE-2026-67103 is a stored/reflected-style Cross-Site Scripting (XSS) vulnerability (CWE-79) affecting HCL BigFix Service Management, an IT service management (ITSM) component within the HCL BigFix endpoint management ecosystem. The flaw allows an attacker with a low-privileged authenticated foothold to inject unsanitized malicious script that executes in a victim user's browser, enabling session hijacking, account takeover, and unauthorized actions performed with the victim's privileges. No public proof-of-concept, exploit code, or vendor patch data exists at time of writing, and CVSS 3.1 rates this 7.6 (High) with scope change, meaning impact crosses a trust boundary from the vulnerable component into the victim's browser session.

Technical Analysis

The vulnerability is classified under CWE-79 (Improper Neutralization of Input During Web Page Generation, i.e., Cross-Site Scripting). Per the NVD description, HCL BigFix Service Management fails to sanitize attacker-supplied input before it is rendered in a victim's browser context. When the injected data is reflected or stored in an HTML/JS response without output encoding, the browser executes the attached script as if it originated from the trusted application origin.

Key CVSS characteristics and what they imply:

• AV:N (Network) — the vulnerability is reachable over the network; no local/physical access required.
• AC:L (Low) — no special conditions or race windows are needed; standard request delivery suffices.
• PR:L (Low) — the attacker requires some authenticated capability (e.g., a low-privileged account within the platform) to submit or place the malicious input.
• UI:R (User Interaction Required) — exploitation depends on a victim navigating to or viewing the poisoned content; this is typical of XSS.
• S:C (Scope Changed) — the security authority of the exploited component does not contain the impact; the script executes in the victim's browser security context, allowing actions outside the vulnerable component's original privilege boundary. This is what elevates the score to High.
• C:H / I:L / A:N — high confidentiality impact (cookie/session/data theft), low integrity impact (limited in-application modification depending on victim role), no availability impact.

The attack surface is the web-facing presentation layer of BigFix Service Management (the browser UI used by service desk agents, administrators, and end users). Because the description does not specify the exact parameter, endpoint, or field, this report does not assert any specific request path, parameter name, or function. The mechanism should be understood at the class level: any BigFix Service Management input that is persisted or reflected into a page and later rendered to another user constitutes a candidate injection point.

No CNA title, affected version list, OSV package mapping, or vendor advisory was provided. No patch source was tracked, and no vendor fix or workaround is documented. EPSS has not been scored by FIRST.org, and CISA KEV does not list this CVE. Consequently, no confirmation of in-the-wild exploitation exists.

Exploitation Scenarios

No public exploit, PoC, or Nuclei template is available. The following chain is inferred strictly from the vulnerability class (CWE-79) and the NVD description. No endpoint, parameter, or function names are asserted because none were provided.

1. Reconnaissance / target identification: The attacker identifies an internet- or intranet-exposed HCL BigFix Service Management instance. This may be done via Shodan/censys queries for BigFix-branded service management portals, or through internal network discovery. The attacker enumerates authentication requirements and determines the privilege level needed to submit input (PR:L implies a low-privileged authenticated account is sufficient).

2. Trigger of the flaw class: Using the authenticated session, the attacker submits crafted input containing script markup into a field or surface that BigFix Service Management renders to other users (a stored XSS path) or reflects back immediately (reflected XSS path). The application does not neutralize/encode the input before embedding it in the HTML response, so the browser treats it as executable content. Because UI:R is set, a victim must load the affected page or view the affected object.

3. Payload/execution (class level): The script executes in the victim's browser session under the BigFix Service Management origin. Attacker objectives at this stage — consistent with the NVD description — are: (a) exfiltrate session cookies/authentication tokens to achieve session hijacking, (b) perform unauthorized in-application actions using the victim's authenticated context (account takeover), and (c) capture data visible to the victim's role.

4. Post-exploitation impact: Successful execution allows the attacker to impersonate the victim within the application (C:H / I:L). With an administrative victim, subsequent actions may include configuration changes relevant to managed endpoints, depending on the privileges held. No further exploitation primitives beyond the browser session are stated in the description; no remote code execution or server compromise is claimed.

Caveat: because the vulnerable version range and exact injection surface are unknown, defenders should treat all unpatched BigFix Service Management deployments as potentially affected and test their specific build against their vendor guidance.

Impact Assessment

Business impact: BigFix Service Management sits in the IT operations/ITSM layer of the enterprise. Compromise of a service desk or administrative session can yield unauthorized access to ticketing data, user records, and — with a high-privileged victim — operational visibility into managed endpoint estate. The CVSS scope-changed rating means the blast radius extends beyond the vulnerable web component into the browser trust context of each victim user.

• Confidentiality: High (C:H). Session tokens, cookies, and page content accessible to the victim can be exfiltrated; with admin victims this may include sensitive configuration and directory data.
• Integrity: Low (I:L). The attacker can perform some unauthorized actions as the victim, but the rating indicates limited scope of modification.
• Availability: None (A:N). No denial-of-service impact is attributed.
• Exploitability: Network-reachable, low complexity, low privilege, user interaction required. This lowers the bar for a motivated insider or an external actor who can obtain a low-privileged account.

Blast radius scale is deployment-dependent. Organizations with a single large BigFix Service Management tenant serving many agents will have a correspondingly larger victim pool, since stored XSS propagates to every user who views the tainted content. Mitigating factor: UI:R and PR:L reduce the likelihood of fully unauthenticated exploitation. Aggravating factor: S:C and C:H make each victim a meaningful loss.

Detection Guidance

Sigma Rule

title: HCL BigFix Service Management XSS Injection Attempt (CVE-2026-67103)
id: 8f2c4d1a-7b3e-4a9c-9d21-bigfixxss2026
status: experimental
description: Detects script-tag and event-handler injection patterns in inbound HTTP requests to HCL BigFix Service Management web endpoints (CWE-79).
references:
  - https://nvd.nist.gov/vuln/detail/CVE-2026-67103
author: valtersit.com Threat Intelligence
date: 2026/01/01
tags:
  - attack.initial_access
  - attack.t1189
  - cve.2026.67103
logsource:
  category: webserver
  product: generic
detection:
  selection_method:
    cs-method:
      - POST
      - GET
  selection_payload:
    - cs-uri-query|contains:
        - '<script'
        - 'javascript:'
        - 'onerror='
        - 'onload='
        - 'onmouseover='
        - '<svg'
        - '<img'
        - 'document.cookie'
        - 'String.fromCharCode'
    - cs-uri-query|re: '(?i)(%3Cscript|%3Csvg|%3Cimg|%22%3E%3C)'
  condition: selection_method and selection_payload
falsepositives:
  - Security scanners and authenticated application testing
  - Legitimate rich-text content containing HTML
level: medium

YARA Rule

rule CVE_2026_67103_BigFix_XSS_Payload
{
    meta:
        description = "Detects common XSS payload markers consistent with CVE-2026-67103 (CWE-79) in HCL BigFix Service Management"
        author = "valtersit.com Threat Intelligence"
        reference = "https://nvd.nist.gov/vuln/detail/CVE-2026-67103"
        date = "2026-01-01"
        severity = "high"
        cve = "CVE-2026-67103"

    strings:
        $s1 = "<script" nocase ascii wide
        $s2 = "javascript:" nocase ascii wide
        $s3 = "onerror=" nocase ascii wide
        $s4 = "onload=" nocase ascii wide
        $s5 = "document.cookie" nocase ascii wide
        $s6 = "String.fromCharCode" nocase ascii wide
        $s7 = "<svg" nocase ascii wide
        $s8 = "fetch(" nocase ascii wide
        $s9 = "XMLHttpRequest" nocase ascii wide
        $bf = "BigFix" nocase ascii wide

    condition:
        $bf and 2 of ($s*)
}

Suricata IDS Rule

alert http any any -> any any (msg:"CVE-2026-67103 Potential XSS Injection HCL BigFix Service Management"; flow:established,to_server; http.method; content:"GET"; http.method; content:"POST"; http.uri; pcre:"/(%3C|<)script|javascript:|onerror\s*=|onload\s*=|%3Csvg|%3Cimg/i"; reference:cve,CVE-2026-67103; reference:url,nvd.nist.gov/vuln/detail/CVE-2026-67103; classtype:web-application-attack; sid:202667103; rev:1;)

Elastic Detection

sequence by source.ip with maxspan=60s
  [network where http.request.method in ("GET","POST") and
     wildcard(http.request.uri.query, "*<script*") or
     wildcard(http.request.uri.query, "*javascript:*") or
     wildcard(http.request.uri.query, "*onerror=*") or
     wildcard(http.request.uri.query, "*%3Cscript*")]

Splunk SPL Query

index=web sourcetype=access_combined
| eval uri_lower=lower(uri)
| where match(uri_lower, "(<|%3c)script|javascript:|onerror\s*=|onload\s*=|%3csvg|document\.cookie|string\.fromcharcode")
| stats count min(_time) as first_seen max(_time) as last_seen
        values(uri) as request_uris values(clientip) as source_ips by host
| where count >= 1
| sort - count

Wazuh OSSEC Rule

<group name="web,appsec,cve_2026_67103,">
  <rule id="202667103" level="10">
    <decoded_as>web-accesslog</decoded_as>
    <url>.*(%3C|<)script.*|.*javascript\:.*|.*onerror\s*=.*|.*%3Csvg.*</url>
    <description>CVE-2026-67103: Possible XSS injection attempt against HCL BigFix Service Management</description>
    <mitre>
      <id>T1189</id>
    </mitre>
    <group>web_attack,xss,</group>
  </rule>
</group>

Mitigation & Patch Guidance

Patch confidence: 0/4 — UNPATCHED. No vendor fix, workaround, or patch reference is available from any tracked source.

1. Immediate mitigations:

   • Treat all HCL BigFix Service Management deployments as potentially affected until HCL publishes a fixed release. Verify your exact build directly with HCL support.
   • Deploy a Web Application Firewall (WAF) in front of the BigFix Service Management portal with XSS rulesets in blocking mode; tune for the application to avoid false positives on rich-text fields.
   • Enforce strict Content-Security-Policy (CSP) headers where the application permits, disallowing inline script (script-src 'self').
   • Set session cookies with HttpOnly, Secure, and SameSite=Strict to blunt session theft via script.
   • Limit administrative sessions; require re-authentication and short session timeouts for privileged users.

2. Patch/upgrade steps:

   • Monitor HCL's security bulletin channel and HCL BigFix release notes for a fix tied to CVE-2026-67103.
   • Once a patched version is released, validate it in a non-production environment, then schedule a staged upgrade. Back up configuration before upgrading.
   • If HCL confirms no fix is planned, apply compensating controls (WAF, CSP, network segmentation) and consider migrating the service management function.

3. Long-term hardening:

   • Integrate context-aware output encoding and input validation into the application development lifecycle so user-supplied data is never rendered unescaped.
   • Adopt a strict CSP and eliminate inline script usage across the portal.
   • Restrict network exposure of ITSM portals to trusted networks/VPN; do not expose service management consoles to the public internet unless strictly necessary.
   • Continuously monitor for CISA KEV updates and vendor advisories; this CVE is not currently in KEV, but XSS flaws are frequently chained into credential-theft campaigns.

References

• NVD — https://nvd.nist.gov/vuln/detail/CVE-2026-67103
• CWE-79 Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting') — https://cwe.mitre.org/data/definitions/79.html
• FIRST EPSS (not yet scored) — https://www.first.org/epss/
• CISA Known Exploited Vulnerabilities Catalog (not listed as of writing) — https://www.cisa.gov/known-exploited-vulnerabilities-catalog
• HCL Security Advisories / BigFix Security Bulletins (consult for vendor patch updates) — https://support.hcl-software.com/

Threat actor campaign / in-the-wild evidence: None available. No public PoC, exploit code, Nuclei template, or KEV listing exists for CVE-2026-67103 at time of writing.