CVE-2021-27877 — An issue was discovered in Veritas Backup Exec before 21.2.¶
Key facts
CVE-2021-27877 is a High (8.2) vulnerability: An issue was discovered in Veritas Backup Exec before 21.2.. This entry ships a detection-only PoC and a Docker test lab. It is on the CISA Known Exploited Vulnerabilities (KEV) catalog (added 2023-04-07), confirming active exploitation in the wild, and is linked to known ransomware campaigns.
Actively exploited — on the CISA KEV catalog
CVE-2021-27877 is listed on the CISA Known Exploited Vulnerabilities (KEV) catalog (added 2023-04-07), confirming exploitation in the wild. It is linked to known ransomware campaigns. Federal remediation deadline: 2023-04-28. Prioritise patching and deploy the detection and prevention rules below.
| CVE | CVE-2021-27877 |
| Severity | High (8.2) |
| CISA KEV | Actively exploited (added 2023-04-07) · ransomware |
| Detection / prevention | — |
| PoC | poc.py |
| Source | 2021/CVE-2021-27877/ |
Details¶
English | 한국어
Description¶
An issue was discovered in Veritas Backup Exec before 21.2. It supports multiple authentication schemes: SHA authentication is one of these. This authentication scheme is no longer used in current versions of the product, but hadn't yet been disabled. An attacker could remotely exploit this scheme to gain unauthorized access to an Agent and execute privileged commands.
Vulnerability Details¶
| Property | Value |
|---|---|
| CVE ID | CVE-2021-27877 |
| CVSS Score | 8.2 |
Proof of Concept¶
Download¶
# Download PoC script
curl -O https://raw.githubusercontent.com/fankh/vulnerability-poc/main/2021/CVE-2021-27877/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-2021-27877
# 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¶
- http://packetstormsecurity.com/files/168506/Veritas-Backup-Exec-Agent-Remote-Code-Execution.html
- https://www.veritas.com/content/support/en_US/security/VTS21-001#issue1
- http://packetstormsecurity.com/files/168506/Veritas-Backup-Exec-Agent-Remote-Code-Execution.html
- https://www.veritas.com/content/support/en_US/security/VTS21-001#issue1
- https://www.cisa.gov/known-exploited-vulnerabilities-catalog?field_cve=CVE-2021-27877
Generated by PoC Generator on 2026-07-12T10:20:04.271857829
Frequently asked questions¶
What is CVE-2021-27877?¶
CVE-2021-27877 is a High (8.2) vulnerability: An issue was discovered in Veritas Backup Exec before 21.2.. This entry ships a detection-only PoC and a Docker test lab. It is on the CISA Known Exploited Vulnerabilities (KEV) catalog (added 2023-04-07), confirming active exploitation in the wild, and is linked to known ransomware campaigns.
How do I detect CVE-2021-27877?¶
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-2021-27877?¶
Upgrade to a fixed version per the vendor advisory; the NVD record lists the affected versions. Use the included PoC to verify your remediation.
Is CVE-2021-27877 actively exploited?¶
Yes. CVE-2021-27877 is on the CISA Known Exploited Vulnerabilities (KEV) catalog, added 2023-04-07, which means it has been exploited in the wild. CISA also links it to known ransomware campaigns. CISA set a federal remediation deadline of 2023-04-28. Prioritise patching and deploy the detection and prevention rules above.
For authorized security testing and research only. See the full source and NVD record.