PSA-2026-00059: Proxmox Backup Server: pxar/container restore target rootfs escape
This Proxmox advisory covers a security issue in Proxmox Backup Server.
Key facts
- Fixed in
- proxmox-backup-client 4.2.7-1
- Advisory id
- PSA-2026-00059
- Source published
- Listed by VulniPulse
Compiled by VulniPulse from the linked sources. How records are collected and checked.
Affected products & platforms
Description
An attacker with direct access to a PBS datastore configured as storage on a Proxmox VE host can construct and upload a malicious pxar archive with two root entries. When such a backup archive was restored by pve-container, the archive contents were written outside of the target rootfs mountpoint.
If a container is restored as privileged container, the extraction runs as root. proxmox-backup-client will now refuse to follow symlinks during extraction of directories or hardlinks. This issue was reported privately by Project Loupe.
Packages: pve-container, proxmox-backup-client, rust-pxar.
Affected product named by the advisory: Proxmox Backup Server.
Text from the source record.
Fix and mitigation
Upgrade to a fixed release named by Proxmox:
- proxmox-backup-client 4.2.7-1
Vendor guidance
- Update to the fixed package versions: proxmox-backup-client >= 4.2.7-1.
End-of-life dates for Proxmox Backup Server
More Proxmox advisories
PSA-2026-00099Nov 10, 2026Proxmox: Incomplete validation of UPID when handling "stop task" API requestsPSA-2026-00087Nov 10, 2026Proxmox Backup Server: Missing privilege check in sync-job modificationPSA-2026-00086Nov 10, 2026Proxmox Backup Server: Missing protections against bogus snapshot creationPSA-2026-00062Oct 7, 2026Proxmox Backup Server: Missing privilege checksPSA-2026-00061Oct 7, 2026Proxmox Backup Server: Missing validation of chunk sizes during pull syncPSA-2026-00060Oct 7, 2026Proxmox Backup Server: Missing privilege checks when removing namespace from prune job
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