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CVE-2026-85526— Path traversal via Btrfs optimized-backup subvolumes[].path enables root file/dir manipulation in LXD

Quick assessment

Affected
Canonical LXD
Exploitation
No confirmed in-the-wild exploitation; assess based on exposure
Recommended action
Check the vendor advisory and references for a fixed version. If immediate upgrade is impossible, restrict exposure and increase monitoring.

Canonical LXD 在 Linux 上的 Btrfs 存储驱动（unpackVolume 函数）中存在路径遍历漏洞。拥有实例创建权限的认证用户，可在导入 Btrfs 优化备份时，通过构造 backup/optimized_header.yaml 文件中的 subvolumes[].path 字段，以 root 权限删除或替换主机文件系统上的任意文件和目录。

CVSS 9.9 · Critical

Possible ATT&CK Techniques 1 AI

T1083 · File and Directory Discovery
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I. Basic Information for CVE-2026-85526

Vulnerability Information
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Vulnerability Title
Path traversal via Btrfs optimized-backup subvolumes[].path enables root file/dir manipulation in LXD
Source: CVE Program / CVE List V5
Vulnerability Description
Path traversal in the Btrfs storage driver (unpackVolume) in Canonical LXD on Linux allows an authenticated user with instance creation privileges to delete or replace arbitrary files and directories on the host filesystem as root via a crafted subvolumes[].path entry in backup/optimized_header.yaml during a btrfs optimized backup import.
Source: CVE Program / CVE List V5
CVSS Information
CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:C/C:H/I:H/A:H
Source: CVE Program / CVE List V5
Vulnerability Type
对路径名的限制不恰当(路径遍历)
Source: CVE Program / CVE List V5

Affected Products

Vendor Product Affected Versions CPE Subscribe
Canonical LXD 4.0.0 ~ 4.0.14 -

II. Public POCs for CVE-2026-85526

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III. Intelligence Information for CVE-2026-85526

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Other References for CVE-2026-85526 (6)

Same Patch Batch · Canonical · 2026-09-28 · 7 CVEs total

CVE-2026-87799 9.9 CRITICAL Arbitrary file write on LXD host via symlink in migration stream
CVE-2026-85185 9.6 CRITICAL Path traversal in LXD btrfs storage driver allows arbitrary file deletion and write on hos
CVE-2026-97335 7.7 HIGH Incorrect authorization in LXD storage volume API allows reading volumes from other projec
CVE-2026-86335 6.3 MEDIUM LXD Cross-Project Private Image Theft via Unsanitized GetImageFromAnyProject Local Reuse
CVE-2026-87798 5.8 MEDIUM LXD client recursive file pull allows directory escape via malicious VM agent
CVE-2026-86334 4.2 MEDIUM CLI Path Traversal via Content-Disposition in LXD Image Export/Copy

IV. Related Vulnerabilities

Same product: LXD
Same vendor: Canonical
Same weakness: CWE-22

V. Comments for CVE-2026-85526

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