CVE-2026-78545

Executive Summary

CVE-2026-78545 is a code injection vulnerability in Okta Access Gateway where the application label field is not sanitized before being interpolated into a generated nginx configuration file, allowing injected nginx directives to execute within a server block. The flaw requires an attacker to already hold high privileges (PR:H) and involves a high attack complexity (AC:H), but successful exploitation yields complete compromise of confidentiality, integrity, and availability (C:H/I:H/A:H). Affected organizations are those running Okta Access Gateway instances where privileged users can define or modify application labels. There is currently no vendor patch, no public proof-of-concept, and no evidence of exploitation in the wild.

Technical Analysis

The vulnerability resides in the configuration generation logic of Okta Access Gateway. According to the NVD description, the product "does not sanitize the application label field before including it in the generated nginx configuration file." The unsanitized value is interpolated into an nginx server block directive, which results in "execution of injected directives."

This is a classic instance of CWE-94 (Improper Control of Generation of Code), specifically a template/configuration injection variant. The application label is intended to be a human-readable identifier for an application integrated with Access Gateway. However, because the label is written directly into an nginx server block without validation or escaping, an attacker who controls the label can inject arbitrary nginx configuration directives. Nginx directives are powerful: they can alter request routing (e.g., proxy_pass), enable server-side includes, expose internal files via alias or root, or change authentication behavior. The injected directives are executed by nginx when the configuration is reloaded or regenerated.

The attack surface is the administrative interface (or API) of Okta Access Gateway that allows management of application labels. The CVSS vector indicates network accessibility (AV:N) but high privileges required (PR:H), meaning the attacker must already be an authenticated administrator or have equivalent rights to define or edit application labels. The high attack complexity (AC:H) suggests that exploitation may require specific conditions—such as a particular nginx version, timing of a configuration reload, or the ability to predict or trigger the generation process—that are not trivially satisfied.

No vendor advisory, patch, or workaround is available. No specific function names, endpoints, or file paths beyond the "application label field" and "generated nginx configuration file" are disclosed in the NVD description; therefore, the exact injection point and the full set of exploitable directives cannot be enumerated without further research.

Exploitation Scenarios

No public proof-of-concept exists for CVE-2026-78545; the following attack chain is inferred from the vulnerability class (CWE-94) and the NVD description.

1. Reconnaissance / Target Identification: The attacker identifies an Okta Access Gateway instance (e.g., via Shodan or internal discovery). They must already possess high-privileged access to the Access Gateway management interface—this could be a compromised administrator account, a malicious insider, or an attacker who has escalated privileges through another vulnerability.

2. Triggering the Flaw Class: Using the privileged access, the attacker navigates to the application management functionality and creates or modifies an application label. Instead of a benign text label, they supply a string containing nginx configuration syntax. Because the application does not sanitize the label, the malicious string is interpolated verbatim into the nginx server block directive that Access Gateway generates.

3. Payload / Execution Method (vulnerability-class level): The injected nginx directives take effect when the configuration is written and nginx is reloaded or restarted. The exact impact depends on the directives injected. For example, directives could redirect traffic to an attacker-controlled server, expose internal files, or disable authentication checks. The NVD description confirms that the injection results in "execution of injected directives," meaning the nginx worker processes will act on the attacker's configuration.

4. Post-Exploitation Impact: Successful exploitation can lead to full compromise of the Access Gateway's confidentiality, integrity, and availability (C:H/I:H/A:H). An attacker could intercept or manipulate authentication traffic, pivot into internal networks, or cause a denial of service by injecting invalid directives that crash nginx. Because Access Gateway often sits in front of critical applications, the blast radius includes all downstream services relying on it for access control.

No public exploit code or Nuclei template is available; the attack chain is inferred from the vulnerability class.

Impact Assessment

The CVSS v3.1 base score is 6.6 (Medium), with the vector CVSS:3.1/AV:N/AC:H/PR:H/UI:N/S:U/C:H/I:H/A:H. The subscores indicate:

• Confidentiality (C:H): Injected nginx directives could expose sensitive internal data, including authentication tokens, session data, or backend application responses.
• Integrity (I:H): Attackers can alter routing, inject content, or modify authentication flows, compromising the integrity of all traffic passing through Access Gateway.
• Availability (A:H): Malicious directives can crash nginx or render the gateway inoperable, causing a denial of service for all protected applications.
• Scope (S:U): The impact is confined to the Access Gateway component and its immediate environment; however, because Access Gateway is a security control, its compromise effectively undermines the security of downstream systems.
• Attack Complexity (AC:H): Exploitation requires conditions beyond the attacker's direct control, such as specific nginx behavior or timing of config reloads.
• Privileges Required (PR:H): The attacker must have administrative access to the Access Gateway management interface.

Business impact is significant for organizations using Okta Access Gateway as a reverse proxy or identity-aware proxy. A compromised gateway can lead to credential theft, man-in-the-middle attacks, and lateral movement into protected applications. The EPSS score is 0.00491 (39.8th percentile), indicating a low probability of exploitation in the next 30 days, and CISA KEV does not list this CVE—so immediate mass exploitation is unlikely. However, the lack of a patch and the high impact make this a critical risk for targeted attacks.

Detection Guidance

Sigma Rule

title: Okta Access Gateway Application Label Injection Attempt
id: 8f4c2b1a-3d5e-4f6a-9b7c-1e2d3f4a5b6c
status: experimental
description: Detects suspicious characters in application label field that may indicate nginx directive injection attempts against Okta Access Gateway.
author: Valters IT Threat Intelligence
date: 2026-01-01
logsource:
  product: okta
  service: access_gateway
detection:
  selection:
    event_type: 'application.label.update'
    label|contains:
      - ';'
      - '{'
      - '}'
      - 'proxy_pass'
      - 'server_name'
      - 'location'
      - 'rewrite'
      - 'return'
      - 'alias'
      - 'root'
  condition: selection
falsepositives:
  - Legitimate application labels containing semicolons or braces (rare)
level: high
tags:
  - attack.t1190
  - cve.2026.78545

YARA Rule

rule CVE_2026_78545_Nginx_Directive_Injection
{
    meta:
        description = "Detects nginx configuration files containing injected directives from Okta Access Gateway application labels"
        author = "Valters IT Threat Intelligence"
        date = "2026-01-01"
        reference = "CVE-2026-78545"
        severity = "high"
    strings:
        $s1 = "proxy_pass" ascii wide nocase
        $s2 = "location" ascii wide nocase
        $s3 = "server_name" ascii wide nocase
        $s4 = "rewrite" ascii wide nocase
        $s5 = "return" ascii wide nocase
        $s6 = "alias" ascii wide nocase
        $s7 = "root" ascii wide nocase
        $injection = /[;{}]\s*(proxy_pass|location|server_name|rewrite|return|alias|root)/ ascii wide
    condition:
        $injection or (2 of ($s*))
}

Suricata IDS Rule

alert http any any -> any any (msg:"CVE-2026-78545 Okta Access Gateway Application Label Nginx Injection Attempt"; flow:to_server,established; content:"application"; http_uri; content:"label"; http_uri; pcre:"/(\%3B|;|\{|\})/Ui"; pcre:"/(proxy_pass|location|server_name|rewrite|return|alias|root)/Ui"; reference:cve,2026-78545; classtype:attempted-admin; sid:202678545; rev:1;)

Elastic Detection

sequence by host.id, user.id with maxspan=5m
  [ process where event.type == "start" and process.name == "nginx" and process.args == "-s" and process.args == "reload" ]
  [ file where file.path : "/etc/nginx/conf.d/*" and file.extension == "conf" and file.content : ("*;*proxy_pass*" or "*};*location*" or "*server_name*;*") ]

Splunk SPL Query

index=okta sourcetype=OktaAccessGateway:admin
| search event_type="application.label.update"
| eval label_lower=lower(label)
| where match(label_lower, "(proxy_pass|location|server_name|rewrite|return|alias|root|;|\{|\})")
| table _time, user, src_ip, application_name, label, event_type
| sort - _time

Wazuh OSSEC Rule

<group name="okta_access_gateway,">
  <rule id="100785" level="12">
    <decoded_as>json</decoded_as>
    <field name="event_type">application.label.update</field>
    <field name="label">\.*[;{}].*</field>
    <description>CVE-2026-78545: Suspicious characters in Okta Access Gateway application label - possible nginx directive injection</description>
    <mitre>
      <id>T1190</id>
    </mitre>
    <group>cve_2026_78545,</group>
  </rule>
  <rule id="100786" level="12">
    <decoded_as>json</decoded_as>
    <field name="event_type">application.label.update</field>
    <field name="label">\.*(proxy_pass|location|server_name|rewrite|return|alias|root).*</field>
    <description>CVE-2026-78545: Nginx directive keyword detected in Okta Access Gateway application label</description>
    <mitre>
      <id>T1190</id>
    </mitre>
    <group>cve_2026_78545,</group>
  </rule>
</group>

Mitigation & Patch Guidance

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

1. Immediate Mitigations:

   • Restrict administrative access to the Okta Access Gateway management interface to only trusted, necessary personnel using least privilege and strong multi-factor authentication.
   • Audit all existing application labels for suspicious characters (semicolons, braces, nginx directive keywords) and remediate any found.
   • Monitor configuration change logs for unauthorized modifications to application labels.
   • If possible, implement a Web Application Firewall (WAF) rule or input validation proxy that blocks nginx metacharacters in label fields.
   • Consider network segmentation to limit the blast radius if the gateway is compromised.

2. Patch/Upgrade Steps:

   • No vendor patch is currently available. Monitor Okta's security advisories and Access Gateway release notes for an official fix.
   • Once a patch is released, test it in a staging environment before deploying to production.
   • Apply the patch immediately upon release, given the high impact (C:H/I:H/A:H).

3. Long-term Hardening:

   • Implement strict input validation and output encoding for all fields that are used in configuration file generation.
   • Adopt a secure configuration generation pattern (e.g., using parameterized templates with proper escaping).
   • Enforce separation of duties so that the ability to define application labels is not combined with the ability to modify nginx configuration.
   • Conduct regular security reviews of configuration generation logic and fuzz testing for injection flaws.
   • Monitor CISA KEV and Okta advisories for updates.

References

• NVD Entry: https://nvd.nist.gov/vuln/detail/CVE-2026-78545
• Okta Security Advisories: https://trust.okta.com/security-advisories/ (monitor for CVE-2026-78545)
• CWE-94: Improper Control of Generation of Code ('Code Injection'): https://cwe.mitre.org/data/definitions/94.html
• MITRE ATT&CK T1190: Exploit Public-Facing Application: https://attack.mitre.org/techniques/T1190/
• EPSS Score: 0.00491 (39.8th percentile) — https://api.first.org/data/v1/epss?cve=CVE-2026-78545

No known threat actor campaigns or exploit-in-the-wild evidence are associated with CVE-2026-78545 at this time. CISA KEV does not list this CVE.