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Canonical LXD CVE-2026-63293

| EUVDEUVD-2026-57540 CRITICAL
Improper Link Resolution Before File Access (CWE-59)
2026-08-12 security@ubuntu.com
9.9
CVSS 3.1 · Vendor: ubuntu
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Attack ChainAIDerived

Hypothetical attack flow derived from CVE metadata – not a confirmed exploit chain

  1. Access
    Obtain LXD image-import privilege
  2. Delivery
    Craft image archive with symlinked metadata.yaml
  3. Exploit
    Push archive to LXD API
  4. Execution
    LXD unpack follows symlink to host path
  5. Persist
    Read or overwrite host file as root
  6. Impact
    Escalate to host compromise

Vulnerability Assessment

Weakness
CWE
OWASP Top 10:2025
A01:2025 - Broken Access Control
ASVS 5.0
V5 - File Handling Symlink resolution safety
Exploitation Conditions

Exploitation requires the attacker to be able to import or unpack an image archive into LXD (an image-management privilege, consistent with PR:L), and to supply a crafted archive whose metadata.yaml entry is a symbolic link pointing to a chosen host path. The exploit is gated by LXD processing that attacker-controlled archive during import/unpack; it does not require user interaction (UI:N) and is reachable over the LXD API network vector (AV:N). Limiting factors: the attacker must already possess image-import rights rather than being fully anonymous, so environments that forbid untrusted users from importing images are not exposed, and successful host impact assumes the LXD daemon runs with sufficient (typically root) privilege to reach the targeted paths.

Impact

The provided CVSS 3.1 vector (AV:N/AC:L/PR:L/UI:N/S:C/C:H/I:H/A:H, 9.9) reflects a genuinely severe primitive - network-reachable via the LXD API, low complexity, scope-changing, and full CIA impact on the host - but PR:L confirms the attacker must already hold some authenticated privilege to import images, so this is not an anonymous internet-wide bug. No EPSS score, KEV entry, POC, or SSVC decision data was supplied, so real-world exploitation likelihood cannot be quantified from the input; the absence of KEV/POC signals means priority rests on the intrinsic severity and the value of the target rather than observed mass exploitation. One consistency note: the reference tag classifies this only as 'Information Disclosure,' which understates the vulnerability - the description and the I:H/A:H metrics indicate arbitrary file WRITE, not just read, so defenders should treat it as an integrity/host-compromise issue, not merely disclosure. Given LXD daemons typically run as root, the write primitive plausibly escalates to full host takeover, making this a real priority wherever untrusted or semi-trusted users can push images.

Exploit ScenarioDerived

A semi-trusted tenant or CI account that holds LXD image-import privileges crafts an image archive in which metadata.yaml is a symlink pointing to a sensitive host file (for example a systemd unit, an authorized_keys file, or /etc configuration). When LXD imports and unpacks the archive, it follows the symlink and reads or overwrites the targeted host path as root, enabling credential theft or code execution on the host. No public exploit code was identified at time of analysis, but the low attack complexity makes weaponization straightforward once the archive format is understood.

Act Now Prioritize within 24-48h. Why: CRITICAL severity.
Patch available 0.4% exploitation probability (EPSS)

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AnalysisAIv1 – Aug 12, 2026

Arbitrary host file read and write in Canonical LXD occurs because the image import/unpack routine does not verify whether the bundled metadata.yaml entry is a symbolic link, letting an authenticated user with image-import rights supply a crafted archive whose symlinked metadata.yaml resolves to sensitive host paths. Rated CVSS 9.9 with a scope change (S:C), successful exploitation crosses the container/management boundary to read or overwrite files as the LXD daemon (typically root) on the host. There is no public exploit identified at time of analysis and the issue is not listed in CISA KEV; details are published only in Canonical advisory GHSA-j825-cg34-5fr5.

RemediationAI

Upgrade LXD to the fixed release identified in Canonical advisory GHSA-j825-cg34-5fr5 (https://github.com/canonical/lxd/security/advisories/GHSA-j825-cg34-5fr5); the exact patched version is not present in the supplied data and must be taken from that advisory rather than assumed. Until patched, restrict who can import or upload images - limit image-import permissions to fully trusted operators and disable image acceptance from untrusted projects or remote users, accepting the trade-off that legitimate self-service image workflows are curtailed. Prefer importing only images from trusted, signed sources and, where feasible, unpack or inspect untrusted archives in an isolated sandbox before importing so a symlinked metadata.yaml cannot resolve against production host paths; note this adds operational overhead to image onboarding. Because the daemon typically runs as root, also review filesystem permissions and API access controls to reduce blast radius.

Affected VersionsENISA

LXD 5.0.0 <5.0.8
LXD 4.0.0 <4.0.12
LXD 6.0 <6.10
LXD 5.21.0 <5.21.6

Affected Packages

euvd lxd fix: 4.0.12, 5.0.8, 5.21.6, 6.10

Source: OSV (Open Source Vulnerabilities)

Affects your stack

Affects 1 package in euvd

Checking this CVE against your own stacks and servers is part of the Basic plan and up.

Technical ContextAI · show details

LXD is Canonical's system container and virtual-machine manager whose daemon (lxd) generally runs as root and exposes a REST API for image management. Images are distributed as archives (unified or split tarballs) that include a metadata.yaml describing the image; during import/unpack LXD reads and processes this file. The flaw is a CWE-59 link-following (symlink) weakness: LXD treats the metadata.yaml path inside the archive as a regular file without checking st_mode/lstat semantics, so a symlink placed at that path is dereferenced against the host filesystem. Because the daemon runs with high privilege and the unpack step operates on host paths, dereferencing an attacker-controlled symlink yields read or write primitives against arbitrary host locations rather than being confined to the image staging directory.

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Severity by source

Vendor (ubuntu) PRIMARY 9.9 CRITICAL
AV:N/AC:L/PR:L/UI:N/S:C/C:H/I:H/A:H
vuln.today AI 9.9 CRITICAL

Reachable via the LXD API (AV:N) with low complexity; requires image-import privilege (PR:L, no UI); crosses container-to-host boundary (S:C) yielding root-level read/write, so C/I/A all High.

3.1 AV:N/AC:L/PR:L/UI:N/S:C/C:H/I:H/A:H
4.0 AV:N/AC:L/AT:N/PR:L/UI:N/VC:H/VI:H/VA:H/SC:H/SI:H/SA:H
SUSE CRITICAL

Primary rating from Vendor (ubuntu).

CVSS VectorVendor: ubuntu

Attack Vector
Network
Attack Complexity
Low
Privileges Required
Low
User Interaction
None
Scope
Changed
Confidentiality
High
Integrity
High
Availability
High

Lifecycle Timeline

2
Patch available
Aug 12, 2026 - 21:17 EUVD
CVE Published
Aug 12, 2026 - 20:17 cve.org
CRITICAL 9.9

DescriptionCVE.org

A link following vulnerability in LXD allows an attacker to achieve arbitrary file read and write operations on the host system. When importing or unpacking an image archive, LXD fails to validate whether the metadata.yaml file is a symbolic link. An attacker can exploit this flaw by providing a crafted image archive with a symlinked metadata.yaml file pointing to target file paths on the host system.

Executive ViewAI

Why It Matters

Canonical LXD contains a critical container escape vulnerability (CVE-2026-63293, CVSS 9.9) enabling authenticated users with image-import rights to read or overwrite arbitrary files on the host operating system with root-level daemon privileges. This crosses the container boundary to compromise the underlying infrastructure, exposing data stored on affected hosts and enabling lateral movement within the environment.

Business Impact: Severe
Compensating Controls

Restrict image-import authorization to minimal set of named administrators; maintain approved image source whitelist and validate all images through external security scanning before import; disable image-import functionality if not mission-critical; isolate LXD environments on restricted network segments with egress controls; implement host-level file integrity monitoring and real-time alerting for modifications to sensitive paths; monitor LXD daemon logs and system call activity for exploitation indicators.

Threat Intelligence Overview

EPSS Score
0.4%
Top 69% exploitable
Prevalence
Medium
common container/VM manager in Ubuntu server estates, not universal
Data Quality
8 sources
Confidence: High
EUVD NVD CVE.org EPSS Vulnrichment Vendor GitHub VulDB

How this decision was reached

The engine reads each signal below and applies a fixed list of rules from top to bottom. The first rule that matches sets the recommended action – like a statement, every line is shown.

SignalValue
Severity CRITICAL
CISA KEV No
Public POC No
EPSS 0.4%
Patch available Yes
Active threat No
Deciding rule
CRITICAL severity
What every action level means
Emergency Immediate action required. Criteria: CRITICAL + in CISA KEV (actively exploited) without patch, OR CRITICAL + EPSS > 30% without patch, OR CRITICAL + active threat signals without patch.
Act Now Prioritize within 24-48h. Criteria: in KEV with patch available, OR CRITICAL + public POC, OR HIGH + EPSS > 10%, OR CRITICAL + active threat, OR any CRITICAL severity.
This Week Schedule remediation this week. Criteria: HIGH severity (CVSS 7.0-8.9). Patch within normal change window.
This Month Plan within 30 days. Criteria: MEDIUM severity (CVSS 4.0-6.9), lower exploitation probability. Include in regular patch cycle.
Monitor Track and reassess. Criteria: LOW severity (CVSS 0.1-3.9), minimal exploitation risk. No immediate action needed.

SSVC AssessmentENISA

SSVC Decision
Out-of-Cycle
Exploitation
Poc
System Exposure· derived
Open
Automatable
No
Human Impact
Very High
Technical Impact
Total

Priority Score

50
Low Medium High Critical
KEV: 0
EPSS: 0
CVSS: +50
PoC: 0
Weaponized: 0
Threat intel: 0
Gov advisory: 0

Attack Technique

Information disclosure occurs when an application unintentionally exposes sensitive data that aids attackers in reconnaissance or directly compromises security.

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Vendor StatusVendor

SUSE

Severity: Critical

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