CVE-2021-26084: Atlassian Confluence Server and Data Center Object-Graph Navigation Language (OGNL) Injection Vulnerability

What it is

In affected versions of Confluence Server and Data Center, an OGNL injection vulnerability exists that would allow an unauthenticated attacker to execute arbitrary code on a Confluence Server or Data Center instance. The affected versions are before version 6.13.23, from version 6.14.0 before 7.4.11, from version 7.5.0 before 7.11.6, and from version 7.12.0 before 7.12.5.

Exploitation evidence

First exploit evidence seen: 2021-08-25 (earliest date across the sources below).

Exploited in the wild

• CISA KEV: listed since 2021-11-03. Source

Public exploit code

Metasploit

• exploit/multi/http/atlassian_confluence_webwork_ognl_injection: Atlassian Confluence WebWork OGNL Injection (disclosure 2021-08-25)

Exploit-DB

• EDB-50243: Confluence Server 7.12.4 - 'OGNL injection' Remote Code Execution (RCE) (Unauthenticated) (2021-09-01)

GitHub proof-of-concept repositories

35 public repositories from 35 accounts, first seen 2021-08-31. Most starred: hev0x/CVE-2021-26084_Confluence (316 stars), view repository.

Verify before running: public PoCs can be malicious. Read the code and only run it in an isolated lab. A PoC means exploit code is public, not that this CVE is exploited in the wild.

Sources: CISA KEV · Rapid7 Metasploit Framework module metadata · Exploit-DB (OffSec) · nomi-sec/PoC-in-GitHub.

How to fix it

CISA required action

Apply updates per vendor instructions. (source: CISA KEV)

Fixed versions

• atlassian confluence data center: upgrade to 6.13.23 or later
• atlassian confluence data center: upgrade to 7.4.11 or later (affected from 6.14.0)
• atlassian confluence data center: upgrade to 7.11.6 or later (affected from 7.5.0)
• atlassian confluence data center: upgrade to 7.12.5 or later (affected from 7.12.0)
• atlassian confluence server: upgrade to 6.13.23 or later
• atlassian confluence server: upgrade to 7.4.11 or later (affected from 6.14.0)
• atlassian confluence server: upgrade to 7.11.6 or later (affected from 7.5.0)
• atlassian confluence server: upgrade to 7.12.5 or later (affected from 7.12.0)

Derived from the NVD CPE configuration (versionEndExcluding / versionEndIncluding). Always confirm with the vendor advisory.

Vendor advisories and patches

• https://jira.atlassian.com/browse/CONFSERVER-67940 (Issue Tracking, Patch, Vendor Advisory)

MITRE ATT&CK mitigations for this chain

• M1033 Limit Software Installation (for T1059) : Prevent user installation of unrequired command and scripting interpreters.
• M1045 Code Signing (for T1059) : Where possible, only permit execution of signed scripts.
• M1042 Disable or Remove Feature or Program (for T1059) : Disable or remove any unnecessary or unused shells or interpreters.
• M1038 Execution Prevention (for T1059) : Use application control where appropriate. For example, PowerShell Constrained Language mode can be used to restrict access to sensitive or otherwise dangerous language elements such as those used to execute arbitrary Windows APIs or files (e.g., `Add-Type`).
• M1049 Antivirus/Antimalware (for T1059) : Anti-virus can be used to automatically quarantine suspicious files.
• M1026 Privileged Account Management (for T1059) : When PowerShell is necessary, consider restricting PowerShell execution policy to administrators. Be aware that there are methods of bypassing the PowerShell execution policy, depending on environment configuration. PowerShell JEA (Just Enough Administration) may also be used to sandbox administration and limit what c
• M1047 Audit (for T1059) : Inventory systems for unauthorized command and scripting interpreter installations.
• M1021 Restrict Web-Based Content (for T1059) : Script blocking extensions can help prevent the execution of scripts and HTA files that may commonly be used during the exploitation process. For malicious code served up through ads, adblockers can help prevent that code from executing in the first place.
• M1040 Behavior Prevention on Endpoint (for T1059) : On Windows 10, enable Attack Surface Reduction (ASR) rules to prevent [Visual Basic](https://attack.mitre.org/techniques/T1059/005) and [JavaScript](https://attack.mitre.org/techniques/T1059/007) scripts from executing potentially malicious downloaded content .

Detection Generic guidance

• Execution: Watch for the service process spawning shells or script interpreters (cmd.exe, powershell, sh, bash, python) via EDR process-tree rules.
• Impact: Monitor service availability, unexpected encryption activity and mass file changes.

Response checklist Generic guidance

1. Inventory: find every instance of the affected product and version (include internet-facing and forgotten ones).
2. Patch or mitigate per the vendor advisory; if you cannot patch, remove internet exposure or apply the vendor workaround.
3. Assume compromise if the system was exposed before patching: hunt for the indicators in the advisory and review logs back to the disclosure date.
4. Rotate credentials and secrets stored on or used by the affected system if compromise cannot be ruled out.