Vulnerability Note VU#555316
STARTTLS plaintext command injection vulnerability
Some STARTTLS implementations could allow a remote attacker to inject commands during the plaintext phase of the protocol.
STARTTLS is an extension to plaintext communication protocols that offers a way to upgrade a plaintext connection to an encrypted (TLS or SSL) connection instead of using a separate port for encrypted communication. Some implementations of STARTTLS contain a vulnerability that could allow a remote unauthenticated attacker to inject commands during the plaintext protocol phase, that will be executed during the ciphertext protocol phase. This vulnerability is caused by the switch from plaintext to TLS being implemented below the application's I/O buffering layer.
This issue is only of practical concern for affected implementations that also perform correct certificate validation. Implementations which do not perform certificate validation are already inherently vulnerable to man-in-the-middle attacks.
Note: Not all implementations of STARTTLS are affected by this vulnerability. Some implementations of Simple Authentication and Security Layer (SASL) could also be affected by this vulnerability. Please see the Vendor Information below for specific vendor information.
A remote attacker with the ability to pose as a man-in-the-middle may be able to inject commands for the corresponding protocol (e.g., SMTP, POP3, etc.) during the plaintext protocol phase, that will then be executed during the ciphertext protocol phase.
Please see the Vendor Information below for specific vendor information and patches.
Purge the application I/O buffer
Developers of STARTTLS-enabled applications should take care to purge the application's I/O buffer immediately after switching to TLS in order to mitigate this vulnerability.
Vendor Information (Learn More)
If you are a vendor and your product is affected, let
us know.View More »
|Vendor||Status||Date Notified||Date Updated|
|Cyrus-IMAP||Affected||-||17 May 2011|
|Debian GNU/Linux||Affected||-||11 May 2011|
|Ipswitch, Inc||Affected||21 Jan 2011||01 Mar 2011|
|Kerio Technologies||Affected||19 Jan 2011||01 Mar 2011|
|Postfix||Affected||-||03 Mar 2011|
|Qmail-TLS||Affected||19 Jan 2011||07 Mar 2011|
|Red Hat, Inc.||Affected||19 Jan 2011||07 Apr 2011|
|Sun Microsystems, Inc.||Affected||19 Jan 2011||01 Mar 2011|
|Ubuntu||Affected||-||11 May 2011|
|Watchguard Technologies, Inc.||Affected||19 Jan 2011||14 Apr 2011|
|Blue Coat Systems||Not Affected||19 Jan 2011||28 Mar 2011|
|EXIM||Not Affected||07 Mar 2011||14 Mar 2011|
|Force10 Networks, Inc.||Not Affected||19 Jan 2011||22 Jul 2011|
|Fortinet, Inc.||Not Affected||19 Jan 2011||16 Mar 2011|
|Global Technology Associates, Inc.||Not Affected||19 Jan 2011||14 Mar 2011|
Thanks to Wietse Venema for reporting this vulnerability.
This document was written by Michael Orlando.
If you have feedback, comments, or additional information about this vulnerability, please send us email.