CVE-2021-21698: Path traversal vulnerability in Jenkins Subversion Plugin allows reading arbitrary files

The vulnerability stems from the lack of path validation in the getKeyFile method before version 2.15.1. The commit diff shows a security check was added to this method to prohibit directory separator characters in the 'id' parameter. Since this method constructs the key file path using Jenkins' root directory + 'subversion-credentials' + untrusted 'id' input, the absence of validation in vulnerable versions allowed path traversal attacks. The direct correlation between the patch location and vulnerability description confirms this function's role in the security flaw.