CVE-2026-78837: AppNitro MachForm SQLI Vulnerability

CVE-2026-78837 Overview

CVE-2026-78837 is a SQL injection vulnerability in AppNitro MachForm v30. The flaw resides in the ap_form_{id} parameter, which fails to sanitize user-supplied input before incorporating it into database queries. Attackers can inject crafted SQL statements to read sensitive information from the backing database. The issue is classified under CWE-89: Improper Neutralization of Special Elements used in an SQL Command. Exploitation requires no authentication and no user interaction, and the vulnerability is remotely reachable over the network. Public proof-of-concept material has been published on GitHub, increasing the likelihood of opportunistic scanning against exposed MachForm deployments.

Critical Impact
Unauthenticated remote attackers can extract sensitive database contents from vulnerable MachForm v30 instances by manipulating the ap_form_{id} parameter.

Affected Products

AppNitro MachForm v30
Web applications embedding MachForm v30 form endpoints
Deployments exposing MachForm forms over the public internet

Discovery Timeline

2026-09-08 - CVE-2026-78837 published to NVD
2026-09-09 - Last updated in NVD database

Technical Details for CVE-2026-78837

Vulnerability Analysis

MachForm v30 accepts the ap_form_{id} parameter on form-handling endpoints and passes the value into a SQL query without proper parameterization. Because the input is concatenated into the query string, an attacker can terminate the intended clause and append arbitrary SQL syntax. The impacted queries expose read access to database contents, enabling data extraction through techniques such as UNION-based injection, error-based inference, and boolean blind injection.

The vulnerability affects confidentiality but does not directly modify data or disrupt service. However, information gathered through injection often includes credential hashes, session records, and administrative metadata, which can enable follow-on account takeover.

The EPSS probability for near-term exploitation is 0.312%, and a public proof-of-concept is available in a GitHub repository maintained by the reporter.

Root Cause

The root cause is missing input validation and the absence of prepared statements when handling the ap_form_{id} parameter. MachForm treats the parameter as trusted numeric input and interpolates it directly into SQL, which allows characters such as single quotes, comments, and UNION operators to alter query structure.

Attack Vector

An unauthenticated attacker submits a crafted HTTP request to a MachForm endpoint that consumes ap_form_{id}. The malicious payload extends the SQL query to read arbitrary rows from tables accessible to the MachForm database user. See the public PoC repository for request-level details.

No exploitation code is reproduced here. Refer to the vendor references and the Packet Storm Security site for published technical write-ups.

Detection Methods for CVE-2026-78837

Indicators of Compromise

HTTP requests to MachForm endpoints containing SQL metacharacters such as ', --, /*, or UNION SELECT within the ap_form_{id} parameter.
Web server logs showing repeated requests to the same form endpoint with incrementing or encoded payloads in ap_form_{id}.
Database error messages surfaced in application responses referencing SQL syntax near ap_form_ values.

Detection Strategies

Deploy web application firewall signatures that inspect the ap_form_{id} parameter for SQL injection patterns and time-based payloads.
Correlate web access logs with database query logs to identify anomalous SELECT statements originating from MachForm processes.
Alert on outbound data transfers from the MachForm host that exceed baseline volumes, which can indicate mass data extraction.

Monitoring Recommendations

Enable verbose HTTP request logging on the reverse proxy or web server fronting MachForm, retaining full query strings and POST bodies.
Monitor authentication tables and administrative accounts for unexpected read access via database audit logging.
Track failed and malformed SQL statements at the database tier to surface probing attempts before successful extraction.

How to Mitigate CVE-2026-78837

Immediate Actions Required

Restrict access to MachForm administrative and form endpoints using network ACLs or VPN gating until a patched build is deployed.
Enable a web application firewall in blocking mode with rules that reject SQL metacharacters in the ap_form_{id} parameter.
Rotate database credentials used by MachForm and review recent database access logs for signs of extraction.

Patch Information

No vendor advisory or patched release is listed in the NVD entry at the time of publication. Consult the AppNitro MachForm product site for updated releases and apply any new version that addresses the ap_form_{id} handling. Until a fix is available, treat all MachForm v30 deployments as vulnerable.

Workarounds

Place MachForm behind an authenticated reverse proxy so unauthenticated internet users cannot reach the vulnerable endpoint.
Configure the MachForm database user with least-privilege permissions limited to the tables the application requires.
Deploy WAF signatures targeting SQL injection patterns in the ap_form_{id} parameter, including URL-encoded and double-encoded variants.

bash

# Example ModSecurity rule to block SQLi payloads in ap_form_{id}
SecRule ARGS_NAMES "@rx ^ap_form_" \
    "chain,id:1026078837,phase:2,deny,status:403,log,\
    msg:'CVE-2026-78837 MachForm ap_form_{id} SQLi attempt'"
    SecRule ARGS "@detectSQLi" "t:none,t:urlDecodeUni"