CVE-2026-16971: IRIS Web App MFA Brute-Force Vulnerability

CVE-2026-16971 Overview

CVE-2026-16971 affects the DFIR-IRIS web application, an open-source incident response investigation platform. Version 2.4.26 and possibly earlier releases fail to protect the multi-factor authentication (MFA) validation endpoint against brute-force attacks. Attackers with knowledge of valid credentials can repeatedly submit MFA codes without rate limiting or account lockout enforcement. The weakness is tracked as [CWE-770: Allocation of Resources Without Limits or Throttling].

Critical Impact
An attacker who already possesses valid username and password credentials can bypass the MFA second factor by brute-forcing time-based one-time passwords, defeating the additional authentication layer.

Affected Products

DFIR-IRIS web application version 2.4.26
Potentially earlier DFIR-IRIS releases with the same MFA implementation
Deployments exposing the IRIS login interface to untrusted networks

Discovery Timeline

2026-07-30 - CVE-2026-16971 published to NVD
2026-07-30 - Last updated in NVD database

Technical Details for CVE-2026-16971

Vulnerability Analysis

DFIR-IRIS implements MFA as a second-stage check after primary username and password authentication. The MFA validation endpoint accepts one-time codes but does not enforce a maximum number of failed attempts, does not apply progressive delays, and does not lock accounts after repeated failures. An attacker who has already obtained a valid password, through phishing, credential stuffing, or database compromise, can iterate through the code space of a standard six-digit TOTP token.

A six-digit TOTP has one million possible values. Without throttling, an attacker with sufficient network bandwidth can submit codes at high rates until one matches the current time window. The high attack complexity reflects the need for prior credential compromise and a valid session state, but the MFA control itself provides no meaningful resistance once that state is reached.

Root Cause

The root cause is missing rate-limiting logic on the MFA verification handler. The application processes each submitted code independently without tracking failed attempt counts per session, per user, or per source IP address. This falls under [CWE-770], which describes the failure to limit resource allocation, in this case the number of authentication guesses permitted.

Attack Vector

The attack vector is network-based and requires no user interaction. The attacker first obtains valid credentials for a target account. They then initiate a login session and reach the MFA challenge. Using an automated script, the attacker submits sequential or randomized six-digit codes to the validation endpoint until authentication succeeds. Refer to the GitHub Security Advisory for the full technical writeup from SBA Research.

No verified public exploit code is available. The vulnerability mechanism is described in prose above; no synthetic proof-of-concept is included here.

Detection Methods for CVE-2026-16971

Indicators of Compromise

High volumes of POST requests from a single source IP address to the IRIS MFA validation endpoint within a short time window
Repeated failed MFA validation events for the same user account followed by a successful authentication
Successful logins preceded by dozens or hundreds of MFA failures in application logs
Authentication sessions where the interval between primary login and MFA success is anomalously long

Detection Strategies

Parse IRIS application logs for MFA validation failure events and alert when the count per session or per user exceeds a threshold
Deploy web application firewall rules that count requests to the MFA endpoint per source IP and flag automated patterns
Correlate authentication telemetry to identify accounts with abnormal ratios of failed to successful MFA attempts

Monitoring Recommendations

Ingest IRIS authentication and reverse-proxy access logs into a centralized logging platform for cross-source correlation
Baseline normal MFA failure rates per user and alert on deviations that exceed the baseline by an order of magnitude
Monitor for successful logins from source IP addresses with recent authentication failure history

How to Mitigate CVE-2026-16971

Immediate Actions Required

Restrict network exposure of the IRIS web interface to trusted networks or place it behind a VPN
Enforce strong, unique passwords for all IRIS accounts to reduce the likelihood of prior credential compromise
Review authentication logs for signs of prior brute-force activity against MFA endpoints

Patch Information

No fixed version is identified in the NVD entry at the time of publication. Administrators should consult the DFIR-IRIS project repository and the GitHub Security Advisory from SBA Research for updated patch availability and remediation guidance.

Workarounds

Deploy a reverse proxy such as nginx or HAProxy in front of IRIS and configure request rate limits on the MFA validation URL
Configure a web application firewall to block source IP addresses that submit more than a small number of MFA attempts per minute
Implement network-layer access controls that restrict IRIS access to known analyst workstations or jump hosts
Rotate credentials and re-enroll MFA tokens for accounts suspected of exposure

bash

# Example nginx rate limit for the MFA validation endpoint
http {
    limit_req_zone $binary_remote_addr zone=mfa_limit:10m rate=5r/m;

    server {
        location /mfa/verify {
            limit_req zone=mfa_limit burst=3 nodelay;
            proxy_pass http://iris_backend;
        }
    }
}