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libcurl SASL buffer overflow vulnerability

February 11, 2013 | Posted in ExploitAlert

libcurl SASL buffer overflow vulnerability
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Project cURL Security Advisory, February 6th 2013
http://curl.haxx.se/docs/security.html

1. VULNERABILITY

libcurl is vulnerable to a buffer overflow vulnerability when communicating
with one of the protocols POP3, SMTP or IMAP.

When negotiating SASL DIGEST-MD5 authentication, the function
Curl_sasl_create_digest_md5_message() uses the data provided from the server
without doing the proper length checks and that data is then appended to a
local fixed-size buffer on the stack.

This vulnerability can be exploited by someone who is in control of a server
that a libcurl based program is accessing with POP3, SMTP or IMAP. For
applications that accept user provided URLs, it is also thinkable that a
malicious user would feed an application with a URL to a server hosting code
targetting this flaw.

This vulnerability can be used for remote code execution (RCE) on vulnerable
systems.

Both curl the command line tool and applications using the libcurl library
are vulnerable.

There is no known exploit for this problem.

The Common Vulnerabilities and Exposures (CVE) project has assigned the name
CVE-2013-0249 to this issue.

2. AFFECTED VERSIONS

Affected versions: curl 7.26.0 to and including 7.28.1
Not affected versions: curl < 7.26.0 and >= 7.29.0

Also note that libcurl is used by many applications, and not always
advertised as such.

3. THE SOLUTION

libcurl 7.29.0 implements proper bounds checking and will not overflow any
buffers even if unrealistically long data chunks are received.

4. RECOMMENDATIONS

We suggest you take one of the following actions immediately, in order of
preference:

A - Upgrade to curl and libcurl 7.29.0

B - Apply this patch and rebuild libcurl

http://curl.haxx.se/curl-sasl.patch

C - Rebuild curl with support for vulnerable protocols IMAP, POP3 and SMTP
disabled.

D - Disable the vulnerable protocols IMAP, POP3 and SMTP at run-time to
forbid libcurl from using them. You can do this with the
CURLOPT_PROTOCOLS option.

5. TIME LINE

Vulnerability found and patched by Volema (http://volema.com/).

It was reported to the curl project on January 30th 2013.

curl 7.29.0 was released on February 6th 2013, coordinated with the
publication of this flaw.

6. CREDITS

Reported and fixed by Volema. Thanks a lot!

Taged in: buffer, libcurl, overflow, vulnerability