CVE-2026-90444: File Transfer Interface RCE Vulnerability

CVE-2026-90444 Overview

CVE-2026-90444 is an operating system command injection vulnerability [CWE-78] affecting a file-transfer interface that later processes uploaded files through system commands. An authenticated attacker can supply a filename containing shell metacharacters. When a downstream automated process constructs a shell command using that filename, the attacker's payload executes with the privileges of the processing account.

The flaw enables arbitrary command execution, tampering with ingested log data, and lateral movement into the internal network. CISA published advisory icsa-26-254-01 describing the issue, indicating relevance to industrial control system environments.

Critical Impact

An authenticated attacker can execute arbitrary operating system commands, read or modify ingested log data, and gain a foothold for lateral movement within the internal network.

Affected Products

• Affected product details are published in the CISA ICS advisory icsa-26-254-01
• Specific vendor and product identifiers are not enumerated in the NVD entry
• Refer to the CISA ICS Advisory icsa-26-254-01 for the authoritative affected component list

Discovery Timeline

• 2026-09-11 - CVE-2026-90444 published to the National Vulnerability Database
• 2026-09-18 - Last updated in NVD database

Technical Details for CVE-2026-90444

Vulnerability Analysis

The vulnerability resides in a file-transfer interface that requires valid credentials but fails to restrict shell metacharacters in user-supplied filenames. After upload, an automated downstream process concatenates the filename into an operating system command string and executes it through a shell. Because the filename is never sanitized or passed through a safe execution API, injected characters such as ;, |, `, $(), or newline sequences break out of the intended command context.

Successful exploitation runs attacker-controlled commands under the identity of the ingestion process. That process typically holds read and write access to log storage, which enables tampering with or deletion of forensic evidence. The command execution primitive also provides an internal network foothold for follow-on activity.

Root Cause

The root cause is improper neutralization of special elements used in an OS command [CWE-78]. The application trusts the filename as opaque data while a downstream component treats it as part of a shell command line. This dual interpretation is the classic condition that enables command injection.

Attack Vector

Exploitation requires network access to the file-transfer interface and valid low-privilege credentials. The attacker uploads a file whose name embeds shell metacharacters and a command payload. When the automated processor later handles the file, the payload executes. No user interaction is required, and attack complexity is low. See the CISA ICS Advisory icsa-26-254-01 for vendor-specific exploitation context.

No verified public exploit code is available at time of writing.
Refer to CISA advisory icsa-26-254-01 for authoritative technical detail.

Detection Methods for CVE-2026-90444

Indicators of Compromise

• Uploaded filenames containing shell metacharacters such as ;, |, &, backticks, $(...), or embedded newlines
• Unexpected child processes spawned by the file ingestion or log-processing service account
• Outbound network connections originating from the ingestion process to unfamiliar internal or external hosts
• Gaps, truncations, or unauthorized modifications in ingested log streams

Detection Strategies

• Inspect application and web server logs for POST or PUT requests whose filename parameters contain shell metacharacters
• Alert on process-lineage anomalies where the file-transfer or ingestion daemon spawns interpreters such as sh, bash, cmd.exe, or powershell.exe
• Correlate file uploads with subsequent process creation and network events using OCSF-normalized telemetry

Monitoring Recommendations

• Enable command-line auditing on hosts running the file-ingestion service and forward events to a centralized SIEM
• Baseline normal child processes of the ingestion account and generate alerts on deviations
• Monitor filesystem writes to log directories for unexpected deletions or modifications that could indicate evidence tampering

How to Mitigate CVE-2026-90444

Immediate Actions Required

• Apply vendor-supplied updates identified in CISA ICS Advisory icsa-26-254-01 as soon as available
• Restrict network access to the file-transfer interface to trusted management networks only
• Rotate credentials used by any account with access to the vulnerable interface
• Audit ingested log data for signs of tampering during the exposure window

Patch Information

Consult the CISA ICS Advisory icsa-26-254-01 for the authoritative list of fixed versions and vendor remediation guidance. The NVD entry does not currently enumerate specific patched versions.

Workarounds

• Enforce strict server-side filename validation that permits only alphanumeric characters, hyphens, underscores, and periods
• Reject or rename uploads whose filenames contain shell metacharacters before any downstream processing
• Refactor downstream automation to pass filenames as argument-array parameters rather than concatenating into shell command strings
• Run the ingestion process under a least-privilege account with no shell access and no write access outside the ingestion working directory

# Example allow-list validation pattern for filenames
# Reject any filename that does not match this regular expression
^[A-Za-z0-9._-]{1,128}$