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STARTTLS plaintext command injection vulnerability

Vulnerability Note VU#555316

Original Release Date: 2011-03-07 | Last Revised: 2011-09-08

Overview

Some STARTTLS implementations could allow a remote attacker to inject commands during the plaintext phase of the protocol.

Description

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.

Impact

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.

Solution

Update

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

555316
 

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CVSS Metrics

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References

Acknowledgements

Thanks to Wietse Venema for reporting this vulnerability.

This document was written by Michael Orlando.

Other Information

CVE IDs: CVE-2011-0411, CVE-2011-1430, CVE-2011-1431, CVE-2011-1432, CVE-2011-1575
Severity Metric: 1.39
Date Public: 2011-03-07
Date First Published: 2011-03-07
Date Last Updated: 2011-09-08 14:58 UTC
Document Revision: 53

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