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GHSA-269q-hmxg-m83q
No affected components available
Description
GHSA-5mcr-gq6c-3hq2 (CVE-2021-21290) contains an insufficient fix for the vulnerability identified.
Impact
When netty's multipart decoders are used local information disclosure can occur via the local system temporary directory if temporary storing uploads on the disk is enabled.
This only impacts applications running on Java version 6 and lower. Additionally, this vulnerability impacts code running on Unix-like systems, and very old versions of Mac OSX and Windows as they all share the system temporary directory between all users.
Vulnerability Details
To fix the vulnerability the code was changed to the following:
@SuppressJava6Requirement(reason = "Guarded by version check")
public static File createTempFile(String prefix, String suffix, File directory) throws IOException {
if (javaVersion() >= 7) {
if (directory == null) {
return Files.createTempFile(prefix, suffix).toFile();
}
return Files.createTempFile(directory.toPath(), prefix, suffix).toFile();
}
if (directory == null) {
return File.createTempFile(prefix, suffix);
}
File file = File.createTempFile(prefix, suffix, directory);
// Try to adjust the perms, if this fails there is not much else we can do...
file.setReadable(false, false);
file.setReadable(true, true);
return file;
}
Unfortunately, this logic path was left vulnerable:
if (directory == null) {
return File.createTempFile(prefix, suffix);
}
This file is still readable by all local users.
Patches
Update to 4.1.77.Final
Workarounds
Specify your own java.io.tmpdir when you start the JVM or use DefaultHttpDataFactory.setBaseDir(...) to set the directory to something that is only readable by the current user or update to Java 7 or above.
References
- CWE-378: Creation of Temporary File With Insecure Permissions
- CWE-379: Creation of Temporary File in Directory with Insecure Permissions
For more information
If you have any questions or comments about this advisory:
Open an issue in netty
The vulnerability requires local access to the device to be exploited. It is easy for an attacker to exploit this vulnerability. An attacker needs basic access or low-level privileges. No user interaction is needed for the attacker to exploit this vulnerability. The impact is confined to the system where the vulnerability exists. There is a high impact on the confidentiality of the information.
Exploitation attempts have been detected. Elevated vigilance and prompt remediation are advised.
The exploit probability is very low. The vulnerability is unlikely to be exploited in the next 30 days.
We did not find any exploit available. Neither in GitHub repositories nor in the Exploit-Database.
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