CVE-2026-78620

Executive Summary

CVE-2026-78620 is an unauthenticated-to-high-privilege file path validation flaw in the Okta Access Gateway Kerberos configuration handler. The application fails to validate file paths supplied within event payloads before writing file contents, allowing an attacker with administrative access to the Kerberos configuration interface to redirect file writes to arbitrary locations on the appliance filesystem. This results in a partial confidentiality and integrity compromise (CVSS 5.9) — an attacker can overwrite sensitive system files or plant malicious content (e.g., web shells, configuration tampering), potentially leading to full appliance takeover depending on the file targeted. No public exploit, patch, or vendor workaround currently exists, and no CISA KEV listing has been published.

Technical Analysis

The vulnerability resides in the Kerberos configuration handler of the Okta Access Gateway (OAG). According to the NVD description, the component processes event payloads containing file path information. When a Kerberos-related configuration event is processed, the handler extracts a file path from the payload and uses it directly as the destination for write operations — without applying path canonicalization, traversal checks, or allowlist validation.

Vulnerability class: This is a textbook CWE-73 — External Control of File Name or Path. The handler fails to neutralize or validate user-supplied path data before using it in filesystem write operations. The flaw is exploitable when the following conditions align:

1. An attacker (or compromised process) can submit event payloads to the Kerberos configuration handler.
2. The payload contains a path field (or equivalent) that is not validated against an expected directory (e.g., a Kerberos keytab or configuration directory).
3. The handler opens that path for writing without checks.

Attack surface considerations:

• The OAG is a public-facing identity gateway — it terminates inbound authentication requests and proxies to backend identity providers. This places it at the network perimeter, typically reachable from the internet.
• The Kerberos configuration handler is part of the administrative/configuration plane. While the CVSS vector indicates PR:H (high privileges required), this reflects the default posture — in many deployments, administrative UIs are exposed to broader networks than necessary, and credential compromise of a low-level admin account could provide sufficient access.
• The CVSS vector AV:N/AC:H also encodes a high attack complexity: the attacker must possess substantial knowledge of the target filesystem layout and the exact format expected by the write routine. Blind exploitation is unlikely; the attacker typically needs a foothold or prior reconnaissance on the appliance's internal structure.

Code-level insight (at the vulnerability-class level):

The handler logically performs an operation similar to:

1. Parse event payload → extract filename/path token.
2. Open file handle using the unvalidated token.
3. Write Kerberos configuration data (e.g., keytab entries, realm mappings) to that handle.

No sanitization function (e.g., realpath(), path.resolve(), or an allowlist check against expected directories like /etc/krb5/) is invoked between steps 1 and 2. This missing validation step is the root cause.

Exploitation Scenarios

Prerequisite conditions: The attacker must be able to reach the Kerberos configuration administrative endpoint and possess valid administrative credentials (or have compromised a service account with such privileges). Public proof-of-concept or exploit code is not available; the following attack chain is inferred from the vulnerability class and NVD description.

Step 1 — Reconnaissance / Target identification: An attacker identifies an Okta Access Gateway appliance exposed to the internet or an internal network (Shodan dork: product:Okta, http.title:"Okta Access Gateway"). The attacker fingerprints the appliance and identifies the administration interface. If direct exposure is absent, the attacker may first compromise a low-privilege service account (phishing, credential stuffing, or lateral movement) that has administrative rights to the OAG configuration plane.

Step 2 — Triggering the flaw class: The attacker authenticates to the Kerberos configuration management interface. They craft a configuration event payload for a new Kerberos configuration — e.g., adding a keytab, realm mapping, or SPN entry. Within this payload, they replace the expected destination path (normally a Kerberos configuration file) with a path traversal sequence or absolute path targeting a sensitive location, such as:

• /etc/passwd or /etc/shadow — to overwrite user credential entries.
• /opt/okta/conf/server.properties — to tamper with application configuration.
• A web-accessible directory (e.g., /opt/okta/www/uploads/backdoor.jsp) — to plant a web shell.

Step 3 — Payload / execution method: Because file contents from the payload are written verbatim, the attacker payload includes both the malicious path token and the malicious data to write. The handler processes the event without validating that the path stays within the permitted Kerberos configuration directory. The write operation succeeds, placing the attacker-controlled data at the arbitrary target location.

Step 4 — Post-exploitation impact: Depending on the file targeted:

• Web shell: Full remote code execution under the OAG service account (likely root or a privileged OS user, as OAG appliances typically run with elevated privileges).
• System file overwrite (e.g., /etc/shadow, /etc/sudoers): Privilege escalation to root, complete system compromise.
• App configuration tampering: Repointing the gateway's upstream identity provider to an attacker-controlled server, allowing credential interception or authentication bypass.

No public PoC exists; this attack chain is inferred solely from the vulnerability description. Real-world exploitation may vary.

Impact Assessment

CVSS breakdown (score 5.9):

• Attack Vector: Network — remotely exploitable.
• Attack Complexity: High — requires specific knowledge of filesystem layout and event payload construction.
• Privileges Required: High — administrative access to the Kerberos configuration handler.
• User Interaction: None.
• Confidentiality Impact: High — writes can target files whose contents then leak sensitive data or overwritten files may expose system information.
• Integrity Impact: High — arbitrary file write allows corruption of configuration, binaries, or data files.
• Availability Impact: None — of the three classic CIA dimensions, availability is not directly compromised, though indirect service outages are possible if critical files are overwritten.

Blast radius assessment:

Affected systems: All Okta Access Gateway appliances running unpatched firmware with Kerberos configuration enabled (the vulnerable feature). Since no version enumeration is available, all current versions prior to an eventual patch are considered vulnerable.

Detection Guidance

Sigma Rule

title: Okta Access Gateway - Suspicious Kerberos Config File Write Path
id: 5f8a2c1b-9f3e-4d7e-b6a1-2c9d3e8f4a7b
status: experimental
description: Detects attempts to write Kerberos configuration files outside expected directories, indicating potential CVE-2026-78620 exploitation.
logsource:
  product: okta
  service: access_gateway
  category: configuration_events
detection:
  selection_kerberos_write:
    EventType: 'KerberosConfigWrite'
    Action: 'WRITE'
  selection_suspicious_path:
    FilePath|contains:
      - '/etc/'
      - '/opt/okta/www/'
      - '/bin/'
      - '/sbin/'
      - '..'
    FilePath|not_contains: '/var/okta/krb5/'
  condition: selection_kerberos_write and selection_suspicious_path
falsepositives:
  - Legitimate administrator writing Kerberos keytabs manually to custom locations
level: high
tags:
  - attack.t1190
  - cve.2026.78620

YARA Rule

rule Okta_Access_Gateway_CVE_2026_78620 {
    meta:
        author = "ValtersIT Threat Intelligence"
        description = "Detects configuration payloads or log entries indicative of CVE-2026-78620 file path traversal in Okta Access Gateway Kerberos handler"
        date = "2026-01-01"
        cve = "CVE-2026-78620"
        cwe = "CWE-73"
        severity = "medium"
    strings:
        $s1 = "KerberosConfig" ascii wide
        $s2 = "keytab" ascii wide
        $s3 = "../" ascii wide
        $s4 = "/etc/shadow" ascii wide
        $s5 = "/opt/okta/www" ascii wide
        $s6 = "realm" ascii wide
        $s7 = "spn" ascii wide
        $s8 = "WRITE" ascii wide
    condition:
        uint16(0) == 0x5A4D or uint32(0) == 0x464C457F or 1
        and
        (2 of ($s1, $s2, $s6, $s7)) and (1 of ($s3, $s4, $s5)) and $s8
}

Suricata IDS Rule

alert http any any -> $HOME_NET any (msg:"Okta Access Gateway CVE-2026-78620 - Kerberos Config Write Payload with Traversal"; flow:established,to_server; content:"POST"; http_method; content:"/config/kerberos"; http_uri; content:"path"; nocase; content:"../"; http_client_body; reference:cve,2026-78620; reference:url,nvd.nist.gov/vuln/detail/CVE-2026-78620; classtype:attempted-admin; sid:200678620; rev:1;)

Note: The HTTP URI /config/kerberos is inferred from the administrative interface pattern — actual endpoint may differ. Adjust the URI match to the observed endpoint pattern in your environment.

Elastic Detection

sequence by host.name with maxspan=5m
  [ network where process.name == "okta-gateway" and event.action == "bind"
      and destination.port >= 443 and destination.port <= 8443 ]
  [ file where process.name == "okta-gateway"
      and event.action in ("write", "create")
      and file.path : ("/etc/*", "/opt/okta/www/*", "/bin/*")
      and not file.path : ("/var/okta/krb5/*", "/tmp/okta-*") ]*

Splunk SPL Query

index=okta sourcetype=okta:oag:config
| where like(FilePath, "%/%") OR like(FilePath, "../%")
| where NOT like(FilePath, "/var/okta/krb5/%")
| where EventType="KerberosConfigWrite"
| eval suspicious_path = if(match(FilePath, "(?i)(/etc/|/sbin/|/usr/bin/|webroot|www/|\.\./)"), "true", "false")
| where suspicious_path="true"
| table _time, src_ip, User, FilePath, WriteResult
| sort - _time

Wazuh OSSEC Rule

<group name="okta,access-gateway,cve-2026-78620,">
  <rule id="100020" level="10">
    <if_sid>8675309</if_sid> <!-- parent syslog rule -->
    <field name="EventType">KerberosConfigWrite</field>
    <field name="FilePath" type="pcre2">(?i)(/etc/|/var/www/|/opt/okta/www/|\.\./)</field>
    <field name="FilePath negate="true" type="pcre2">^/var/okta/krb5/</field>
    <description>Okta Access Gateway: CVE-2026-78620 file path traversal in Kerberos config write</description>
    <group>attacks,</group>
    <mitre><id>1078</id><tactic>Defense Evasion</tactic></mitre>
    <mitre><id>1083</id><tactic>Collection</tactic></mitre>
  </rule>
</group>

Mitigation & Patch Guidance

Patch confidence: 0/4 — UNPATCHED. No vendor advisory, patch release, or security update exists at the time of writing. Okta has not acknowledged the vulnerability publicly, and no CVSS vector rescoring has occurred.

1. Immediate Mitigations

• Restrict administrative network access: Place the OAG administrative interface on a management VLAN accessible only by authorized administrators via jump host. If your deployment exposes admin interfaces on the public internet, block port access immediately (limit to corporate IP ranges/CIDR via firewall ACL).
• Disable Kerberos configuration handler if Kerberos is not actively used in your identity federation chain. If Kerberos integration is idle but enabled, disabling the handler eliminates the attack surface entirely.
• File integrity monitoring (FIM): Deploy or strengthen FIM on the OAG appliance, especially on system-critical paths (/etc/, /opt/okta/). Any unauthorized writes trigger immediate alerts.
• Monitor for suspicious configuration events: Enable verbose audit logging for the OAG config API and Kerberos event handler. Capture the Sigma/Elastic/Splunk rules above with adjusted field mappings for your environment.
• Network access control: Ensure the OAG appliance cannot initiate egress connections to the internet or other network segments except those required for its identity proxy function. This limits the utility of a web shell planted via this flaw.

2. Patch / Upgrade Steps

• None available. Monitor Okta's security advisory page (help.okta.com → Security Advisories) for CVEs affecting Okta products.
• Subscribe to Okta's CVE notification mailing list to receive immediate notification when OAG patch is published.
• Once a patch is released: upgrade OAG appliance to the audited version, then verify the Kerberos handler now performs canonical path validation (test by attempting to write to /tmp via malformed path).

3. Long-Term Hardening

• Least-privilege service accounts: Ensure OAG appliance administrative accounts are separate from broader domain admin credentials. Use PAM (Privileged Access Management) to require temporary, ephemeral credentials.
• Security logging aggregation: Forward OAG audit and access logs to a SIEM (Splunk, Elastic, or equivalent) with correlation rules for this CVE and similar path traversal attempts across all your proxies/gateways.
• Regular vulnerability scanning: Include OAG appliances in scheduled authenticated vulnerability scans (e.g., Tenable, Qualys, Rapid7) — not just unauthenticated network scans, which miss administrative plane issues like this one.
• Segmentation: Place OAG in a DMZ with strict east-west traffic rules. It should not have unrestricted access to the internal Okta tenant network.

References

1. NVD Entry: https://nvd.nist.gov/vuln/detail/CVE-2026-78620
2. CWE-73 Reference (MITRE): https://cwe.mitre.org/data/definitions/73.html — External Control of File Name or Path
3. CISA KEV (confirmed not listed): https://www.cisa.gov/known-exploited-vulnerabilities-catalog — CVE-2026-78620 is not listed.
4. Okta Security Advisory Page (monitor for patch announcement): https://help.okta.com/okta/help/en-us/content/topics/security/security-advisories.htm
5. FIRST.org CVSS Calculator (reference vector): https://www.first.org/cvss/calculator/3.1#CVSS:3.1/AV:N/AC:H/PR:H/UI:N/S:U/C:H/I:H/A:N

Threat actor activity: No known campaigns, exploit-in-the-wild evidence, or threat actor mentions are associated with CVE-2026-78620 at publication time. EPSS score has not been generated by FIRST.org, indicating very low exploitation likelihood in the short term.