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AUSCERT External Security Bulletin Redistribution
libcurl SASL buffer overflow vulnerability
8 February 2013
AusCERT Security Bulletin Summary
Operating System: Windows
UNIX variants (UNIX, Linux, OSX)
Impact/Access: Execute Arbitrary Code/Commands -- Remote with User Interaction
CVE Names: CVE-2013-0249
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libcurl SASL buffer overflow vulnerability
Project cURL Security Advisory, February 6th 2013
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
Both curl the command line tool and applications using the libcurl library
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.
We suggest you take one of the following actions immediately, in order of
A - Upgrade to curl and libcurl 7.29.0
B - Apply this patch and rebuild libcurl
C - Rebuild curl with support for vulnerable protocols IMAP, POP3 and SMTP
D - Disable the vulnerable protocols IMAP, POP3 and SMTP at run-time to
forbid libcurl from using them. You can do this with the
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.
Reported and fixed by Volema. Thanks a lot!
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