Multiple Unix/Linux Vendor cURL/libcURL Kerberos
iDEFENSE Security Advisory 02.21.05:
February 21, 2005
cURL is a command line tool for transferring files with
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' implementation of cURL could allow for
execution on the targeted host.
An exploitable stack-based buffer overflow condition
exists when using
Kerberos authentication. The problem specifically
exists within the
functions Curl_krb_kauth() and krb4_auth() defined in
Within these functions a statically allocated
stack-based buffer of size
1250, from struct KTEXT_ST.dat, is passed to the
routine defined in lib/base64.c as can be seen here:
len = Curl_base64_decode(p, (char *)adat.dat);
tmp = Curl_base64_decode(p, (char *)tkt.dat);
The Curl_base64_decode() routine relies on the calling
validate the decoded length. This function base64
decodes and copies
data directly from the HTTP reply of a server to the
in this case buffer. An attacker can construct a long
malicious payload that upon decoding will overflow the
static buffer and
overwrite the saved EIP. This in turn can lead to
Successful exploitation allows remote attackers to
under the privileges of the target user. Exploitation
requires that an
attacker either coerce or force a target to connect to
server using Kerberos authentication.
iDEFENSE has confirmed the existence of this
vulnerability in cURL
version 7.12.1. It is suspected that prior versions are
Any application built using a vulnerable version
libcURL will also be
Recompile cURL without Kerberos support if it is not
VI. VENDOR RESPONSE
No vendor response received.
VII. CVE INFORMATION
A Mitre Corp. Common Vulnerabilities and Exposures
(CVE) number has not
been assigned yet.
VIII. DISCLOSURE TIMELINE
12/23/2004 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.
Get paid for vulnerability research
X. LEGAL NOTICES
Copyright (c) 2005 iDEFENSE, Inc.
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to be accurate
at the time of publishing based on currently available
of the information constitutes acceptance for use in an
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