AI analysis
CVE-2026-78254 is a path traversal flaw (CWE-23) in the ftp and scp download tasks of Apache Ant: in versions prior to 1.10.18, a server providing downloaded files can use relative paths to write outside the dedicated destination directory. It is triggered when an Ant build uses the ftp or scp task to fetch files from a malicious server, or via a machine-in-the-middle attack against plain ftp; for scp and ftps, the attacking server must still pass the tasks' server identity checks. A successful attack lets the attacker overwrite files of their choosing on the machine running the build, using the permissions of the user executing Ant, potentially tampering with scripts, libraries, or build outputs. Affected users are those running Apache Ant builds (before 1.10.18) that download files with the ftp or scp tasks, especially against servers that are not fully trusted or are reached over untrusted networks. No exploitation is currently known: there is no public proof-of-concept, the flaw is not in CISA's KEV, and EPSS estimates only a 0.4% probability of exploitation within 30 days.
What to do: Upgrade to Apache Ant 1.10.18, which by default prevents these tasks from writing outside the destination directory. Do not bypass server identity checks for scp and ftps, and switch ftp tasks from plain ftp to ftps where possible to prevent machine-in-the-middle attacks. Audit build files for ftp/scp download usage and restrict them to trusted, verified servers until patched.
Affected
| Apache Ant | all versions prior to 1.10.18 |
Estimated exposure
—No basis for an estimate.
Order-of-magnitude estimate by the model from install counts, market share and public scan data it knows; verify before quoting.
Description
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 have to be malicious or be subject to a machine-in-the-middle attack. Additionally in the case of scp or the ftp task using ftps the server must pass the server identity checks performed by the tasks. For ftp tasks not using ftps a malicious server could act as a machine-in-the-middle to provide malicious files. Starting with Ant 1.10.18 both tasks will prevent writing outside of the destination directory by default. An option is available to disable this behavior in the unlikely case that the old behavior is required by existing build files. Mitigations: Users of scp and ftp (when using ftps) in any version of Ant should not bypass server identity checks. Users of ftp not using ftps should switch to ftps where possible. All users are recommended to upgrade to Apache Ant 1.10.18, which fixes this issue.