Vulnerability

PreparedStatement.setText(int, InputStream) and

PreparedStatemet.setBytea(int, InputStream)

will create a temporary file if the InputStream is larger than 51k

Example of vulnerable code:

java String s = "some very large string greater than 51200 bytes";

PreparedStatement.setInputStream(1, new ByteArrayInputStream(s.getBytes()) ); This will create a temporary file which is readable by other users on Unix like systems, but not MacOS.

Impact On Unix like systems, the system's temporary directory is shared between all users on that system. Because of this, when files and directories are written into this directory they are, by default, readable by other users on that same system.

This vulnerability does not allow other users to overwrite the contents of these directories or files. This is purely an information disclosure vulnerability.

When analyzing the impact of this vulnerability, here are the important questions to ask:

Is the driver running in an environment where the OS has other untrusted users. If yes, and you answered 'yes' to question 1, this vulnerability impacts you. If no, this vulnerability does not impact you. Patches Because certain JDK file system APIs were only added in JDK 1.7, this this fix is dependent upon the version of the JDK you are using.

Java 1.8 and higher users: this vulnerability is fixed in 42.2.27, 42.3.8, 42.4.3, 42.5.1 Java 1.7 users: this vulnerability is fixed in 42.2.27.jre7 Java 1.6 and lower users: no patch is available; you must use the workaround below. Workarounds If you are unable to patch, or are stuck running on Java 1.6, specifying the java.io.tmpdir system environment variable to a directory that is exclusively owned by the executing user will fix this vulnerability.

References CWE-200: Exposure of Sensitive Information to an Unauthorized Actor Fix commit https://github.com/pgjdbc/pgjdbc/commit/9008dc9aade6dbfe4efafcd6872ebc55f4699cf5 Similar Vulnerabilities Google Guava - https://github.com/google/guava/issues/4011 Apache Ant - https://nvd.nist.gov/vuln/detail/CVE-2020-1945 JetBrains Kotlin Compiler - https://nvd.nist.gov/vuln/detail/CVE-2020-15824

Impact SQL injection is possible when using the non-default connection property preferQueryMode=simple in combination with application code that has a vulnerable SQL that negates a parameter value.

There is no vulnerability in the driver when using the default query mode. Users that do not override the query mode are not impacted.

Exploitation

To exploit this behavior the following conditions must be met:

1. A placeholder for a numeric value must be immediately preceded by a minus (i.e. -) 1. There must be a second placeholder for a string value after the first placeholder on the same line. 1. Both parameters must be user controlled.

The prior behavior of the driver when operating in simple query mode would inline the negative value of the first parameter and cause the resulting line to be treated as a -- SQL comment. That would extend to the beginning of the next parameter and cause the quoting of that parameter to be consumed by the comment line. If that string parameter includes a newline, the resulting text would appear unescaped in the resulting SQL.

When operating in the default extended query mode this would not be an issue as the parameter values are sent separately to the server. Only in simple query mode the parameter values are inlined into the executed SQL causing this issue.

Example

java PreparedStatement stmt = conn.prepareStatement("SELECT -?, ?"); stmt.setInt(1, -1); stmt.setString(2, "\nWHERE false --"); ResultSet rs = stmt.executeQuery();

The resulting SQL when operating in simple query mode would be:

sql SELECT --1,' WHERE false --'

The contents of the second parameter get injected into the command. Note how both the number of result columns and the WHERE clause of the command have changed. A more elaborate example could execute arbitrary other SQL commands.

Patch Problem will be patched upgrade to 42.7.2, 42.6.1, 42.5.5, 42.4.4, 42.3.9, 42.2.28, 42.2.28.jre7

The patch fixes the inlining of parameters by forcing them all to be serialized as wrapped literals. The SQL in the prior example would be transformed into:

sql SELECT -('-1'::int4), (' WHERE false --')

Workarounds Do not use the connection propertypreferQueryMode=simple. (NOTE: If you do not explicitly specify a query mode then you are using the default of extended and are not impacted by this issue.)