Unauthenticated RCE in Kestra via /configs Authentication Bypass

Repository contains two files: a README describing CVE-2026-53576 and a standalone Python exploit script, kestra_exploit.py. The script is the primary entry point and uses the requests library to interact directly with Kestra’s HTTP API. It targets Kestra OSS <= 1.3.20 and abuses an authentication bypass on API paths ending in /configs to achieve unauthenticated remote code execution. Exploit flow: (1) create a malicious Kestra flow containing an io.kestra.plugin.scripts.shell.Commands task with attacker-controlled shell commands, (2) trigger execution of that flow through the executions API, (3) optionally poll execution status, (4) optionally create and run a second flow to test Docker socket access, and (5) optionally delete the malicious flow. The default payload writes id output to /tmp/proof.txt and appends the first line of /etc/shadow, demonstrating command execution and privileged file access. Main capabilities include arbitrary command execution, reading sensitive files, optional post-exploitation Docker daemon probing via /var/run/docker.sock, and cleanup of artifacts. The exploit is operational rather than a simple PoC because it automates the full attack chain and supports custom commands, HTTPS, configurable ports, delays, and cleanup. No external C2 is hardcoded in the script itself; network targets are supplied by the operator at runtime. The README includes illustrative reverse-shell, exfiltration, and cloud-metadata examples, but those are examples rather than built-in behavior.

This repository is a standalone Python-based Kestra vulnerability scanner/exploit utility for CVE-2026-49869 and CVE-2026-53576. It is not tied to a major exploit framework. The codebase is small and organized around a CLI entry point (main.py) and a scanner module (modules/scanner.py) that contains the core target parsing, URL construction, HTTP probing, and reporting logic. Supporting modules provide banners, ANSI colors, and dataclasses for probe/scan results. Primary capability: it detects an authentication bypass caused by Kestra accepting any request path ending in /configs instead of strictly matching /api/v1/configs. The scanner first checks liveness/version via GET /api/v1/configs, then verifies that the normal flows endpoint requires authentication, and finally probes multiple crafted bypass paths under flows, executions, namespaces/kv, dashboards, logs, and templates. If bypass responses differ from the protected baseline, the target is marked vulnerable. Beyond detection, the tool includes active exploitation features. In aggressive mode it sends PUT requests to confirm unauthorized write access by creating a minimal flow or KV entry. With --rce it performs a full exploit chain: deploys a malicious Kestra flow through the bypass path, triggers execution through the executions bypass endpoint, polls logs for a unique marker plus command output such as id and hostname, and then cleans up the flow. The README states a fallback from shell.Commands to python.Script if needed. With --ssrf it deploys a flow containing Pebble http() calls to AWS, GCP, Azure metadata services and localhost/internal endpoints, then checks execution logs for indicators. With --destructive it tests unauthorized DELETE operations against flows, dashboards, and logs. Repository structure: README.md documents the vulnerability, probe matrix, CLI usage, JSON schema, and affected versions. main.py handles argument parsing, single/bulk scan orchestration, JSON report generation, and exit codes. modules/scanner.py is the main implementation and defines constants such as default tenant main, namespace tutorial, auto-expanded ports [8080, 8081, 8088, 8091, 80, 443], request timeout, polling intervals, and URL builder helpers for the vulnerable endpoints. modules/result.py defines ProbeResult and ScanResult dataclasses used throughout reporting. modules/colors.py and modules/banners.py are cosmetic. requirements.txt shows the tool depends mainly on requests, urllib3, and colorama. Overall, this is an operational exploit/scanner rather than a simple detector: it can validate unauthorized read/write access, confirm code execution, test SSRF reachability, and exercise destructive actions against exposed Kestra instances.