Add PoC exploit for CVE-2021-26084

[postmodern]

Add a PoC exploit for CVE-2021-26084, an OGNL injection vulnerability exists that would allow an unauthenticated attacker to execute arbitrary code on a Confluence Server or Data Center <6.13.23, >=6.14.0 <7.4.11, >=7.5.0 >7.11.6, and >=7.12.0 <7.12.5.

Reference PoCs

• https://github.com/antx-code/CVE-2021-26084/blob/main/CVE-2021-26084.py
• https://github.com/lleavesl/CVE-2021-26084/blob/main/CVE-2021-26084_Confluence_OGNLInjection.py
• https://github.com/TheclaMcentire/CVE-2021-26084_Confluence/blob/main/rce.py

Vuln App

• https://github.com/vulhub/vulhub/tree/639e32be6c0425b11d7d56594761c5e599a6a9d5/confluence/CVE-2021-26084

How to Submit a PoC

See the CONTRIBUTING file for instructions on how to submit a PoC exploit.