CVE-2026-106558 — Backstage is an open framework for building developer portals.¶
Key facts
CVE-2026-106558 is a High (8.8) vulnerability: Backstage is an open framework for building developer portals.. This entry ships a detection-only PoC and a Docker test lab.
| CVE | CVE-2026-106558 |
| Severity | High (8.8) |
| Detection / prevention | — |
| PoC | poc.py |
| Source | 2026/CVE-2026-106558/ |
Details¶
English | 한국어
Description¶
Backstage is an open framework for building developer portals. Prior to 1.14.8, 1.15.6, and 2.0.1, the @backstage/plugin-techdocs-node package improperly validated mapping-style markdown_extensions configuration. An authenticated attacker who can register or influence an SCM-backed documentation source may bypass TechDocs sanitization and cause Python objects to be imported and instantiated in the generator runtime, leading to arbitrary code execution. Earlier fixes in versions 1.14.6 and 1.15.4 did not fully address the supported mapping representation of markdown_extensions. Impact is greatest when documentation generation runs with backend credentials, filesystem access, or internal network access. This issue is fixed in versions 1.14.8, 1.15.6, and 2.0.1.
Vulnerability Details¶
| Property | Value |
|---|---|
| CVE ID | CVE-2026-106558 |
| Type | RCE |
| CVSS Score | 8.8 |
Proof of Concept¶
Download¶
# Download PoC script
curl -O https://raw.githubusercontent.com/fankh/vulnerability-poc/main/2026/CVE-2026-106558/poc.py
Usage¶
# Run PoC against target
python3 poc.py --target <TARGET_URL>
# With authentication
python3 poc.py --target <TARGET_URL> --username <USER> --password <PASS>
⚠️ Warning: This PoC is for authorized security testing only. It uses detection-only techniques and does not exploit or damage target systems.
Test Lab¶
This repository includes a Docker-based test environment with both vulnerable and patched applications.
Quick Start¶
# Clone and navigate to CVE directory
cd CVE-2026-106558
# Start both applications
docker-compose up -d
# Run tests
./run-tests.sh # Linux/Mac
./run-tests.ps1 # Windows PowerShell
Application Endpoints¶
| Application | URL | Status |
|---|---|---|
| Vulnerable App | http://localhost:8080 | Shows vulnerability |
| Patched App | http://localhost:8081 | Demonstrates fix |
Directory Structure¶
├── README.md # English documentation
├── README_KO.md # Korean documentation
├── poc.py # PoC detection script
├── docker-compose.yml # Container orchestration
├── run-tests.sh # Linux/Mac test runner
├── run-tests.ps1 # Windows test runner
├── vulnerable-app/ # Vulnerable version
│ ├── app.py
│ ├── Dockerfile
│ └── requirements.txt
└── patched-app/ # Fixed version
├── app.py
├── Dockerfile
└── requirements.txt
References¶
- https://github.com/backstage/backstage/commit/32723a0fe4e12ed80535fc65d5331765c55aa91b
- https://github.com/backstage/backstage/commit/944edb51c8524d3664b18f2d57ba101b1c93b709
- https://github.com/backstage/backstage/commit/f18e9abcc6051491862b15e4fc60e69f8d52310c
- https://github.com/backstage/backstage/releases/tag/v1.50.7
- https://github.com/backstage/backstage/releases/tag/v1.54.9
- https://github.com/backstage/backstage/releases/tag/v1.55.2
- https://github.com/backstage/backstage/security/advisories/GHSA-qmw3-745m-w99g
Generated by PoC Generator on 2026-10-08T16:08:11.492797648
Frequently asked questions¶
What is CVE-2026-106558?¶
CVE-2026-106558 is a High (8.8) vulnerability: Backstage is an open framework for building developer portals.. This entry ships a detection-only PoC and a Docker test lab.
How do I detect CVE-2026-106558?¶
Run the detection-only PoC included with this entry against your Docker test lab to confirm whether a target is affected; pair it with your own IDS logging.
How do I block or mitigate CVE-2026-106558?¶
Upgrade to a fixed version per the vendor advisory; the NVD record lists the affected versions. Use the included PoC to verify your remediation.
For authorized security testing and research only. See the full source and NVD record.