The ftp and scp tasks of Apache Ant can download files from a remote server. A malicious server can provide relative paths that allow it to write outside of the dedicated target directory for the download, making it possible to overwrite files of the attacker's choice using the permissions of the user running Ant in versions prior to Ant 1.10.18. In order to exploit this vulnerability, the server would either …
When reading a specially crafted TAR archive an Apache Ant build can be made to allocate large amounts of memory that finally leads to an out of memory error, even for small inputs. This can be used to disrupt builds using Apache Ant.
When reading a specially crafted ZIP archive, or a derived formats, an Apache Ant build can be made to allocate large amounts of memory that leads to an out of memory error, even for small inputs. This can be used to disrupt builds using Apache Ant. Commonly used derived formats from ZIP archives are for instance JAR files and many office files.
As mitigation for CVE-2020-1945 Apache Ant 1.10.8 changed the permissions of temporary files it created so that only the current user was allowed to access them. Unfortunately the fixcrlf task deleted the temporary file and created a new one without said protection, effectively nullifying the effort. This would still allow an attacker to inject modified source files into the build process.
Apache Ant uses the default temporary directory identified by the Java system property java.io.tmpdir for several tasks and may thus leak sensitive information. The fixcrlf and replaceregexp tasks also copy files from the temporary directory back into the build tree allowing an attacker to inject modified source files into the build process.