CVE-2019-13118 - Improper Input Validation

Severity

50%

Complexity

99%

Confidentiality

48%

In numbers.c in libxslt 1.1.33, a type holding grouping characters of an xsl:number instruction was too narrow and an invalid character/length combination could be passed to xsltNumberFormatDecimal, leading to a read of uninitialized stack data.

In numbers.c in libxslt 1.1.33, a type holding grouping characters of an xsl:number instruction was too narrow and an invalid character/length combination could be passed to xsltNumberFormatDecimal, leading to a read of uninitialized stack data.

CVSS 3.0 Base Score 7.5. CVSS Attack Vector: network. CVSS Attack Complexity: low. CVSS Vector: (CVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N).

CVSS 2.0 Base Score 5. CVSS Attack Vector: network. CVSS Attack Complexity: low. CVSS Vector: (AV:N/AC:L/Au:N/C:P/I:N/A:N).

Demo Examples

Improper Input Validation

CWE-20

This example demonstrates a shopping interaction in which the user is free to specify the quantity of items to be purchased and a total is calculated.


               
...

The user has no control over the price variable, however the code does not prevent a negative value from being specified for quantity. If an attacker were to provide a negative value, then the user would have their account credited instead of debited.

Improper Input Validation

CWE-20

This example asks the user for a height and width of an m X n game board with a maximum dimension of 100 squares.


               
.../* board dimensions */
die("No integer passed: Die evil hacker!\n");
die("No integer passed: Die evil hacker!\n");
die("Value too large: Die evil hacker!\n");

While this code checks to make sure the user cannot specify large, positive integers and consume too much memory, it does not check for negative values supplied by the user. As a result, an attacker can perform a resource consumption (CWE-400) attack against this program by specifying two, large negative values that will not overflow, resulting in a very large memory allocation (CWE-789) and possibly a system crash. Alternatively, an attacker can provide very large negative values which will cause an integer overflow (CWE-190) and unexpected behavior will follow depending on how the values are treated in the remainder of the program.

Improper Input Validation

CWE-20

The following example shows a PHP application in which the programmer attempts to display a user's birthday and homepage.


               
echo "Birthday: $birthday<br>Homepage: <a href=$homepage>click here</a>"

The programmer intended for $birthday to be in a date format and $homepage to be a valid URL. However, since the values are derived from an HTTP request, if an attacker can trick a victim into clicking a crafted URL with <script> tags providing the values for birthday and / or homepage, then the script will run on the client's browser when the web server echoes the content. Notice that even if the programmer were to defend the $birthday variable by restricting input to integers and dashes, it would still be possible for an attacker to provide a string of the form:


               
2009-01-09--

If this data were used in a SQL statement, it would treat the remainder of the statement as a comment. The comment could disable other security-related logic in the statement. In this case, encoding combined with input validation would be a more useful protection mechanism.

Furthermore, an XSS (CWE-79) attack or SQL injection (CWE-89) are just a few of the potential consequences when input validation is not used. Depending on the context of the code, CRLF Injection (CWE-93), Argument Injection (CWE-88), or Command Injection (CWE-77) may also be possible.

Improper Input Validation

CWE-20

This function attempts to extract a pair of numbers from a user-supplied string.


               
}
die("Did not specify integer value. Die evil hacker!\n");
/* proceed assuming n and m are initialized correctly */

This code attempts to extract two integer values out of a formatted, user-supplied input. However, if an attacker were to provide an input of the form:


               
123:

then only the m variable will be initialized. Subsequent use of n may result in the use of an uninitialized variable (CWE-457).

Improper Input Validation

CWE-20

The following example takes a user-supplied value to allocate an array of objects and then operates on the array.


               
}
list[0] = new Widget();
die("Negative value supplied for list size, die evil hacker!");

This example attempts to build a list from a user-specified value, and even checks to ensure a non-negative value is supplied. If, however, a 0 value is provided, the code will build an array of size 0 and then try to store a new Widget in the first location, causing an exception to be thrown.

Improper Input Validation

CWE-20

This application has registered to handle a URL when sent an intent:


               
}......
}
}
int length = URL.length();
...

The application assumes the URL will always be included in the intent. When the URL is not present, the call to getStringExtra() will return null, thus causing a null pointer exception when length() is called.

Overview

First reported 5 years ago

2019-07-01 02:15:00

Last updated 4 years ago

2020-05-29 00:15:00

Affected Software

XMLSoft libxslt 1.1.33

1.1.33

References

20190816 APPLE-SA-2019-8-13-1 Additional information for APPLE-SA-2019-7-22-2 macOS Mojave 10.14.6, Security Update 2019-004 High Sierra, Security Update 2019-004 Sierra

20190816 APPLE-SA-2019-8-13-2 Additional information for APPLE-SA-2019-7-22-1 iOS 12.4

20190816 APPLE-SA-2019-8-13-3 Additional information for APPLE-SA-2019-7-22-4 watchOS 5.3

20190816 APPLE-SA-2019-8-13-4 Additional information for APPLE-SA-2019-7-22-5 tvOS 12.4

20190723 APPLE-SA-2019-7-22-2 macOS Mojave 10.14.6, Security Update 2019-004 High Sierra, Security Update 2019-004 Sierra

20190723 APPLE-SA-2019-7-22-1 iOS 12.4

20190723 APPLE-SA-2019-7-22-4 watchOS 5.3

20190723 APPLE-SA-2019-7-22-5 tvOS 12.4

20190726 APPLE-SA-2019-7-23-3 iCloud for Windows 10.6

20190726 APPLE-SA-2019-7-23-1 iCloud for Windows 7.13

20190726 APPLE-SA-2019-7-23-2 iTunes for Windows 12.9.6

[oss-security] 20191117 Nokogiri security update v1.10.5

https://bugs.chromium.org/p/oss-fuzz/issues/detail?id=15069

Permissions Required

https://gitlab.gnome.org/GNOME/libxslt/commit/6ce8de69330783977dd14f6569419489875fb71b

Patch, Third Party Advisory

[debian-lts-announce] 20190722 [SECURITY] [DLA 1860-1] libxslt security update

FEDORA-2019-fdf6ec39b4

https://oss-fuzz.com/testcase-detail/5197371471822848

Permissions Required

20190814 APPLE-SA-2019-8-13-1 Additional information for APPLE-SA-2019-7-22-2 macOS Mojave 10.14.6, Security Update 2019-004 High Sierra, Security Update 2019-004 Sierra

20190814 APPLE-SA-2019-8-13-3 Additional information for APPLE-SA-2019-7-22-4 watchOS 5.3

20190814 APPLE-SA-2019-8-13-4 Additional information for APPLE-SA-2019-7-22-5 tvOS 12.4

20190814 APPLE-SA-2019-8-13-2 Additional information for APPLE-SA-2019-7-22-1 iOS 12.4

20190723 APPLE-SA-2019-7-22-1 iOS 12.4

20190723 APPLE-SA-2019-7-22-4 watchOS 5.3

20190723 APPLE-SA-2019-7-22-5 tvOS 12.4

20190724 APPLE-SA-2019-7-23-3 iCloud for Windows 10.6

20190724 APPLE-SA-2019-7-23-1 iCloud for Windows 7.13

20190724 APPLE-SA-2019-7-23-2 iTunes for Windows 12.9.6

https://security.netapp.com/advisory/ntap-20190806-0004/

https://security.netapp.com/advisory/ntap-20200122-0003/

https://support.apple.com/kb/HT210346

https://support.apple.com/kb/HT210348

https://support.apple.com/kb/HT210351

https://support.apple.com/kb/HT210353

https://support.apple.com/kb/HT210356

https://support.apple.com/kb/HT210357

https://support.apple.com/kb/HT210358

USN-4164-1

https://www.oracle.com/security-alerts/cpujan2020.html

openSUSE-SU-2020:0731

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