The XRootD project provides a high-performance, fault-tolerant, and secure solution for handling large amounts of data distributed across multiple storage resources. Prior to version 5.9.2, XRootD's rpCheck() function in src/XrdXrootd/XrdXrootdXeq.cc rejects a parent-directory component only when two dots are followed by a slash and does not reject a terminal two-dot component. An unauthenticated attacker can append /.. to an exported path in xrdfs ls or an HTTP PROPFIND request, bypass the all.export directory scope, and cause directory and filename enumeration in the parent directory under oss.localroot. The demonstrated vector does not permit file download or disclose file contents. This issue is fixed in version 5.9.2.

Affected: PyPI: xrootd

## Summary

A path traversal vulnerability in XRootD allows users to escape the exported directory scope and enumerate the contents of the parent directory by appending `/..` (specifically without trailing slash) to an exported path in `xrdfs ls` or `HTTP PROPFIND` requests.

This bypass ignores the `all.export` restriction.

## Affected component

`src/XrdXrootd/XrdXrootdXeq.cc`, and more precisely the functions `rpCheck()` and `Squash()` used in `do_Dirlist()` ([link](https://github.com/xrootd/xrootd/blob/19aa6dee76906fb4d56ded55e49bbe4171ade915/src/XrdXrootd/XrdXrootdXeq.cc#L696)), as they do not check if the path ends with ".." (without trailing slash). Then the path is passed directly to the filesystem layer.

## PoC

### Configuration

- **Configuration file:** ```conf xrd.port 1094

# Exposing only /alice/ oss.localroot /srv/xrootd/data/ all.export /alice/

# HTTP xrd.protocol http:1094 libXrdHttp.so

# Logs / monitoring all.adminpath /var/spool/xrootd all.pidpath /var/run/xrootd ```

- **Filesystem layout on the server:** ``` /srv/xrootd/data/ ├── alice/ ← only exported directory ├── bob/ ← not exported └── secret.txt ← not exported ```

- **Starting the server:** `xrootd -c /etc/xrootd/xrootd.cfg`

### Steps to reproduce

**Normal behavior (access outside export is denied):** ```bash $ xrdfs root://<xrootd-server> ls / [ERROR] Server responded with an error: [3010] Stating path '/' is disallowed. ```

**Bypass via trailing `..`:** ```bash $ xrdfs…

Affected: Ubuntu:22.04:LTS: xrootd, Ubuntu:24.04:LTS: xrootd, Ubuntu:26.10: xrootd, Ubuntu:26.04:LTS: xrootd

The XRootD project provides a high-performance, fault-tolerant, and secure solution for handling large amounts of data distributed across multiple storage resources. Prior to version 5.9.2, XRootD's rpCheck() function in src/XrdXrootd/XrdXrootdXeq.cc rejects a parent-directory component only when two dots are followed by a slash and does not reject a terminal two-dot component. An unauthenticated attacker can append /.. to an exported path in xrdfs ls or an HTTP PROPFIND request, bypass the all.export directory scope, and cause directory and filename enumeration in the parent directory under oss.localroot. The demonstrated vector does not permit file download or disclose file contents. This issue is fixed in version 5.9.2.