CVE-2021-29425: 
Java vulnerability analysis and mitigation

CVE-2021-29425 is a path traversal vulnerability discovered in Apache Commons IO versions before 2.7. When invoking the method FileNameUtils.normalize with an improper input string, like '//../foo' or '..oo', the result would be the same value, thus possibly providing access to files in the parent directory, but not further above (thus 'limited' path traversal), if the calling code would use the result to construct a path value (CVE Mitre).

The vulnerability exists in the FileNameUtils.normalize method implementation. When processing path strings containing specific patterns like '//../foo' or '..oo', the method fails to properly sanitize these inputs, resulting in a limited path traversal vulnerability. The issue is considered of moderate severity, as it only allows traversal to the immediate parent directory (Apache JIRA).

If exploited, this vulnerability could allow attackers to access files in the parent directory of the intended directory, potentially leading to unauthorized access to sensitive files. The impact is limited since the traversal is restricted to one directory level up, preventing access to files further up in the directory structure (Debian Security).

The recommended mitigation is to upgrade Apache Commons IO to version 2.7 or later. For systems that cannot be immediately upgraded, careful validation of input strings before passing them to FileNameUtils.normalize is advised (NetApp Security).

The vulnerability has received attention from various organizations and has led to security patches across multiple products that depend on Apache Commons IO. Multiple vendors including Oracle, NetApp, and Debian have issued advisories and patches for their affected products (Oracle CPU, NetApp Security).