CVE-2026-54337: Fireshare Argument Injection RCE Vulnerability

CVE-2026-54337 Overview

CVE-2026-54337 is an argument injection vulnerability in Fireshare, a self-hosted media and link sharing platform. The flaw exists in the video upload function and allows an unauthenticated remote attacker to write or overwrite arbitrary files on the host system. All versions prior to 1.6.14 are affected. The maintainers addressed the issue in version 1.6.14.

The vulnerability is tracked under CWE-88: Argument Injection and is documented in GitHub Security Advisory GHSA-hmh2-6g84-q8jx.

Critical Impact
Unauthenticated attackers can write or overwrite system files, enabling remote code execution and full compromise of the Fireshare host.

Affected Products

Fireshare versions prior to 1.6.14
Self-hosted Fireshare deployments exposed over the network
Container-based Fireshare installations sharing volumes with the host

Discovery Timeline

2026-09-15 - CVE-2026-54337 published to the National Vulnerability Database (NVD)
2026-09-16 - Last updated in NVD database

Technical Details for CVE-2026-54337

Vulnerability Analysis

Fireshare exposes a video upload endpoint that passes user-supplied data into a downstream command or external process. The upload handler does not sufficiently validate or sanitize input before it is concatenated into the argument list of the underlying process invocation. An attacker can craft input that is interpreted as additional command-line flags rather than data.

Because the endpoint is reachable without authentication, any attacker able to reach the Fireshare service over the network can trigger the flaw. The result is arbitrary file write, including overwrite of files owned by the Fireshare service account.

Root Cause

The root cause is improper neutralization of argument delimiters (CWE-88). User-controlled fields are appended to a command line without being separated by an explicit argument terminator or validated against an allowlist. Values beginning with - or -- are consumed as options by the target binary, subverting the intended invocation.

Attack Vector

Exploitation occurs over the network against the video upload endpoint. The attacker submits a specially crafted upload request in which fields such as the filename or parameter values inject additional flags to the media-processing binary invoked by Fireshare. Those flags redirect output to attacker-chosen paths, resulting in file overwrite. Writing to locations such as web root files, cron directories, or SSH configuration can be chained to remote code execution.

No verified public proof-of-concept code is referenced by the advisory. Refer to GHSA-hmh2-6g84-q8jx for maintainer-provided technical details.

Detection Methods for CVE-2026-54337

Indicators of Compromise

Uploaded filenames or form fields containing leading - or -- sequences, or option-like tokens targeting the media-processing binary.
Unexpected file writes under the Fireshare working directory, web root, or system paths such as /etc, /var/spool/cron, or ~/.ssh.
Fireshare service process spawning child processes with unusual output-redirection arguments.

Detection Strategies

Inspect Fireshare application and reverse-proxy logs for POST requests to the video upload endpoint containing suspicious argument-like tokens in multipart fields.
Monitor process execution telemetry for Fireshare invoking media-processing binaries with attacker-controlled -o, -f, or similar output flags.
Alert on file creation or modification events attributed to the Fireshare service account outside its expected media directories.

Monitoring Recommendations

Enable file integrity monitoring on directories writable by the Fireshare service account and on adjacent system paths.
Forward Fireshare access logs and host process telemetry to a centralized data lake for correlation across upload requests and file writes.
Baseline normal Fireshare child-process command lines and alert on deviations, particularly new output paths.

How to Mitigate CVE-2026-54337

Immediate Actions Required

Upgrade Fireshare to version 1.6.14 or later without delay.
Restrict network exposure of the Fireshare upload endpoint to trusted networks or behind an authenticating reverse proxy until patching is complete.
Audit the Fireshare host for unexpected file modifications, new persistence artifacts, and unauthorized accounts.

Patch Information

The Fireshare maintainers released version 1.6.14 to remediate the argument injection in the video upload function. Deploy the fixed release from the project repository and restart the service. See GHSA-hmh2-6g84-q8jx for advisory details.

Workarounds

Place Fireshare behind a reverse proxy that enforces authentication for all upload paths.
Run Fireshare as an unprivileged user in a container with a read-only root filesystem and minimal writable volume mounts.
Apply network access control lists to limit inbound traffic to the Fireshare port to known administrator IP ranges.

bash

# Example: restrict Fireshare exposure with an iptables allowlist
iptables -A INPUT -p tcp --dport 8080 -s 10.0.0.0/24 -j ACCEPT
iptables -A INPUT -p tcp --dport 8080 -j DROP