cURL is a command line tool for transferring files with URL syntax,
supporting FTP, FTPS, HTTP, HTTPS, GOPHER, TELNET, DICT, FILE and LDAP.
More information about cURL and libcURL is available from:
Remote exploitation of a stack-based buffer overflow in various Unix /
Linux vendors implementations of cURL could allow for arbitrary code
execution on the targeted host.
An exploitable stack-based buffer overflow condition exists when using
NT Lan Manager (NTLM) authentication. The problem specifically exists
within Curl_input_ntlm() defined in lib/http_ntlm.c. Within this
function an unsigned stack-based character array of size 256, buffer,
is passed to the Curl_base64_decode() routine defined in lib/base64.c as
can be seen here:
size_t size = Curl_base64_decode(header, (char *)buffer);
The Curl_base64_decode() routine relies on the calling function to
validate the decoded length. This function base64 decodes and copies
data directly from the HTTP reply of a server to the destination buffer,
in this case buffer. An attacker can construct a long base64 encoded
malicious payload that upon decoding will overflow the 256 byte static
buffer and overwrite the saved EIP. This in turn can lead to arbitrary
Successful exploitation allows remote attackers to execute arbitrary code
under the privileges of the target user. Exploitation requires that an
attacker either coerce or force a target to connect to a malicious
server using NTLM authentication.
iDEFENSE has confirmed the existence of this vulnerability in cURL
version 7.12.1. It is suspected that prior versions are affected as well.
Any application built using a vulnerable version libcURL will also be
Replace the static buffer allocation on line 106 in lib/http_ntlm.c:
unsigned char buffer;
With a dynamic buffer allocation:
unsigned char *buffer = (unsigned char *)malloc(strlen(header));
and recompile cURL.
No vendor response received.
The Common Vulnerabilities and Exposures (CVE) project has assigned the
names CAN-2005-0490 to these issues. This is a candidate for inclusion
in the CVE list (http://cve.mitre.org), which standardizes names for
12/21/2004 Initial vendor notification - No response
02/10/2005 Secondary vendor notification - No response
02/21/2005 Public disclosure
infamous41md[at]hotpop.com is credited with this discovery.
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Copyright © 2005 Verisign, Inc.
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