CVE-2026-52793

Executive Summary

CVE-2026-52793 is an improper authentication vulnerability (CWE-287) in Froxlor, an open-source server administration panel, affecting all versions prior to 2.3.7. The flaw resides in the API authentication path, where the RPC validation routine fails to enforce second-factor (TOTP/2FA) requirements even when the targeted account has two-factor authentication enabled. An attacker in possession of valid API credentials for a 2FA-protected account can invoke the full set of available API functions without supplying the configured second factor. This enables unauthorized read and modification of customer data, domains, email/FTP accounts, databases, DNS records, and certificate material, with a CVSS base score of 8.1 (High).

Technical Analysis

The vulnerability is classified as CWE-287 (Improper Authentication), indicating that the authentication mechanism accepts insufficient credentials or fails to apply an additional required authentication factor. The NVD description provides the following specific implementation details:

• The vulnerable code path is located in lib/Froxlor/Api/FroxlorRPC.php and is handled by the FroxlorRPC::validateAuth method.
• The authentication flow validates the API key and secret for an administrator or customer account.
• The validation logic checks the API credentials, expiration, API permission, and account status.
• Critically, the validation does not:
  • Check type_2fa (the account's 2FA configuration flag),
  • Validate a TOTP code,
  • Invoke FroxlorTwoFactorAuth.

The web interface enforces a second factor for accounts with 2FA enabled. The API path does not share this enforcement. This is a classic "forgotten alternate authentication path" weakness, where a security control (TOTP) is applied to one interface but not propagated to another.

The attack surface is network-reachable (AV:N), requires low privilege (PR:L — the attacker must possess valid API credentials, which would typically be issued to administrators or resellers/customers with API access), and requires no user interaction (UI:N). The scope is unchanged (S:U), and the impact is high for both confidentiality (C:H) and integrity (I:H). Availability is not directly impacted (A:N).

No detailed source-level analysis beyond the identified file and method names is possible from the provided data. The vulnerability class, however, is well understood: a missing additional authentication factor in an alternate access path (API) that otherwise mirrors the same account authentication logic as the web interface.

Exploitation Scenarios

Preconditions:

• The attacker must possess a valid API key and API secret for an administrator or customer account in Froxlor.
• The targeted account must have two-factor authentication enabled (type_2fa set), and the API key must not be expired.
• The account's API permission must allow the specific function calls the attacker intends to make.

Attack Chain:

1. Reconnaissance / Target Identification: The attacker identifies a Froxlor instance (versions < 2.3.7) exposed on the network. This can be done via internet-wide scanning for the Froxlor login page or API endpoint. The attacker may obtain API credentials through phishing, credential stuffing, config file exposure, insider access, or prior successful account compromise at the single-factor level.

2. Flaw Trigger: The attacker submits an API request to the Froxlor RPC endpoint (FroxlorRPC). The request includes the stolen API key and secret for a 2FA-enabled account. Because FroxlorRPC::validateAuth performs credential validation but omits the 2FA enforcement check (no type_2fa check, no TOTP validation, no call to FroxlorTwoFactorAuth), the request is authenticated successfully with only the API key/secret pair.

3. Payload / Execution Method: At the vulnerability-class level, this is a "credential-based authentication bypass of a secondary factor" flaw. The attacker simply invokes standard API functions using the valid credentials. No specialized payload is required — the request is a legitimate API call with legitimate (but insufficiently-verified) credentials.

4. Post-Exploitation Impact: With API access granted, the attacker can invoke API functions that expose or modify customer data, domains, email accounts, FTP accounts, databases, DNS records, and certificate material. This allows data exfiltration, service disruption through configuration tampering, credential harvesting (e.g., extracting FTP/email credentials), and potential lateral movement into hosted services (since the attacker can modify the server administration panel configuration).

Note: No public PoC or exploit code has been confirmed. The attack chain above is inferred strictly from the NVD description and the vulnerability class. Insufficient technical detail is available to describe exact payload structures or API function invocation details.

Impact Assessment

CVSS v3.1 Subscore Analysis:

• Attack Vector: Network (AV:N) — remotely exploitable.
• Attack Complexity: Low (AC:L) — no special conditions required beyond credential possession.
• Privileges Required: Low (PR:L) — requires valid API credentials; this is not an unauthenticated vulnerability.
• User Interaction: None (UI:N).
• Scope: Unchanged (S:U).
• Confidentiality Impact: High (C:H) — full read access to customer data, domains, credential material, DNS records, and certificates.
• Integrity Impact: High (I:H) — ability to modify all of the above.
• Availability Impact: None (A:N).

Business Impact:

• Data Breach: Customer PII, email credentials, FTP credentials, and database credentials can be exfiltrated.
• Integrity Loss / Defacement: An attacker can modify DNS records, domain configurations, and hosted account settings, redirecting traffic or taking down services for legitimate tenants.
• Certificate Compromise: Exposure of certificate material can enable man-in-the-middle attacks against hosted domains.
• Reputational Damage: As a hosting control panel, Froxlor handles sensitive multi-tenant data. A breach risks trust erosion and regulatory penalties (GDPR, PCI-DSS where applicable).
• Lateral Movement: Via email/FTP/database credentials, attackers can pivot into underlying hosted applications.

Affected Systems: All Froxlor installations running versions prior to 2.3.7, specifically those that have enabled the API and have accounts with 2FA enabled.

Blast Radius: Any hosted customer data on the affected Froxlor instance. A single compromised API credential for one account can affect all data manageable by that account's API permissions. High-privilege accounts (administrators) can modify virtually all panel configuration.

Detection Guidance

The following detection signatures are modeled on the vulnerability description and are intended to flag anomalous API authentication behavior in Froxlor. Because no specific exploit payload byte patterns are known, detection should focus on authentication anomalies rather than specific malicious signatures.

Sigma Rule

title: Froxlor API Authentication Without 2FA Verification
id: 8f6d9b2e-3c1a-4e7d-9f62-5a2d0e8b4f11
status: experimental
description: Detects API authentication attempts in Froxlor where a 2FA-enabled account authenticates via the API without a corresponding TOTP verification, exploiting CVE-2026-52793.
author: Valtersit Threat Intelligence Team
date: 2026/05/15
references:
    - https://nvd.nist.gov/vuln/detail/CVE-2026-52793
logsource:
    product: froxlor
    category: application
    definition: Froxlor application logs configured to capture API authentication events. Requires the Froxlor admin log to record API login attempts, including a flag for 2FA status.
detection:
    selection:
        api_endpoint: "FroxlorRPC"
        auth_method: "api_key_secret"
        account_2fa_enabled: "true"
    filter_known_good:
        totp_verified: "true"
    condition: selection and not filter_known_good
falsepositives:
    - Legitimate API usage if Froxlor changes behavior to require 2FA and the log records TOTP verification.
    - Accounts not enrolled in 2FA (excluded by account_2fa_enabled condition).
level: high
tags:
    - attack.t1190
    - attack.initial_access
    - cve.2026-52793

YARA Rule

rule CVE_2026_52793_Froxlor_API_Auth_Bypass
{
    meta:
        author = "Valtersit.com - Threat Intelligence"
        description = "Detects Froxlor API authentication requests that may indicate exploitation of CVE-2026-52793 (2FA bypass in API auth path)."
        date = "2026-05-15"
        reference = "https://nvd.nist.gov/vuln/detail/CVE-2026-52793"
        severity = "high"
    strings:
        $s1 = "FroxlorRPC" ascii wide
        $s2 = "validateAuth" ascii wide
        $s3 = "api_key" ascii wide
        $s4 = "api_secret" ascii wide
        $s5 = "FroxlorTwoFactorAuth" ascii wide
        $s6 = "type_2fa" ascii wide
    condition:
        (uint16(0) == 0x5A4D or uint16(0) == 0x4D5A or uint32(0) == 0x464C457F) and
        all of ($s1, $s2, $s3, $s4) and
        #s5 == 0 and #s6 == 0
}

Suricata IDS Rule

alert http any any -> any any (
    msg:"CVE-2026-52793 - Froxlor API 2FA Bypass Attempt";
    flow:established,to_server;
    content:"POST"; http_method;
    content:"FroxlorRPC"; http_uri; fast_pattern;
    content:"api_key"; http_client_body;
    content:"api_secret"; http_client_body;
    content:"validateAuth"; distance:0;
    reference:cve,2026-52793;
    classtype:attempted-user;
    sid:10052793;
    rev:1;
)

Elastic Detection

// Elastic EQL — detect Froxlor API authentication calls
// that do not contain references to 2FA/TOTP verification
sequence by host.name
    [ network where destination.port == 80 or destination.port == 443 ]

    any where process.name : "php-fpm*" or process.name : "apache*" or process.name : "nginx*"
    and event.category == "web"
    and http.request.method == "POST"
    and http.request.body.text : "*FroxlorRPC*"
    and http.request.body.text : "*validateAuth*"
    and not http.request.body.text : "*totp*"
    and not http.request.body.text : "*type_2fa*"
    and not http.request.body.text : "*FroxlorTwoFactorAuth*"

Splunk SPL Query

index=webserver OR index=http
    ("FroxlorRPC" OR "validateAuth")
    AND method="POST"
    AND NOT body IN ("*totp*", "*type_2fa*", "*FroxlorTwoFactorAuth*")
    | stats count by src_ip, uri_path, user_agent, _time
    | where count > 5
    | table _time, src_ip, uri_path, user_agent, count

Wazuh OSSEC Rule

<group name="web, froxlor,">
    <rule id="100527" level="12">
        <if_sid>31505</if_sid>  <!-- Apache access log event -->
        <match>FroxlorRPC</match>
        <regex>POST.*validateAuth</regex>
        <description>Froxlor API 2FA bypass attempt (CVE-2026-52793) - API auth without 2FA references</description>
        <group>authentication_failure,</group>
        <mitre>
          <id>T1190</id>
        </mitre>
        <info type="cve">2026-52793</info>
    </rule>
</group>

Mitigation & Patch Guidance

Patch Confidence: 0/4 — UNPATCHED. No patch evidence has been verified from any tracked source. The NVD description states the issue is fixed in version 2.3.7; however, no patch diff, advisory, or vendor confirmation has been confirmed by our sources. Treat as unpatched until vendor verification is obtained.

Immediate Mitigations (until patch is confirmed applied):

1. Disable API access on all Froxlor instances, or restrict API access to only accounts that do NOT have 2FA enabled (temporarily disabling 2FA for API-only accounts is a stopgap, not a fix).
2. Rotate all API keys/secrets immediately if there is any suspicion of compromise. Assume existing keys are compromised if exposed in logs, config backups, or an internal breach.
3. Add IP allowlisting at the network/firewall level for the API endpoint. Restrict authorized API clients to specific source IPs.
4. Monitor all API authentication logs for logins without a TOTP verification event. Generate alerts for any API session that does not have a corresponding 2FA verification record.
5. Enable MFA enforcement at the network layer (e.g., VPN or SSO with MFA in front of the Froxlor API) to compensate for the missing 2FA enforcement inside the application.

Patch/Upgrade Steps:

1. Verify the current Froxlor version: froxlor version check via panel footer or CLI.
2. Upgrade to Froxlor 2.3.7 or later as soon as sourced. The vendor states the fix is in 2.3.7.
3. After upgrade, verify that validateAuth performs a type_2fa check and invokes FroxlorTwoFactorAuth for accounts with 2FA enabled. If not, contact the vendor for clarification.
4. Re-test API authentication with a 2FA-enabled account: a valid API key/secret alone must not succeed in invoking API functions.
5. Rotate all API keys after the upgrade.

Long-Term Hardening:

1. Assume credential compromise: Treat API keys as sensitive secrets, rotate them regularly, and use ephemeral credentials where possible.
2. Principle of least privilege: Grant API permissions only to accounts that require them, and limit API permission scopes.
3. Enable 2FA on all accounts, including service accounts and API-only accounts, and verify enforcement on ALL access paths (web, API, CLI).
4. Network segmentation: Place the Froxlor control panel behind a VPN or a firewalled management VLAN not directly reachable from the internet. If public API access is required, use a WAF with rate limiting and anomaly detection.
5. Integrate threat intelligence: Subscribe to vendor notifications and NVD alerts for Froxlor to receive immediate patch announcements.

References

1. NVD Entry for CVE-2026-52793: https://nvd.nist.gov/vuln/detail/CVE-2026-52793
2. Froxlor Project — Official Website/Source: https://froxlor.org/
3. MITRE ATT&CK Technique T1190 — Exploit Public-Facing Application: https://attack.mitre.org/techniques/T1190/
4. CWE-287 — Improper Authentication: https://cwe.mitre.org/data/definitions/287.html
5. Froxlor GitHub Repository (release notes for 2.3.7): https://github.com/Froxlor/Froxlor/releases

Footnote: As of this report, CVE-2026-52793 is not listed in the CISA Known Exploited Vulnerabilities catalog, no public exploit code has been confirmed, and EPSS has not yet assigned a score. Threat actor campaigns leveraging this specific CVE have not been identified in open-source intelligence at the time of writing. The exploitation scenario is derived from the vulnerability class and the NVD description; no additional technical specifics are available.