Security readout for executives and security teams
Plain-English summary
An authenticated Incus user can use a specially prepared image to make the instance metadata API read or overwrite arbitrary host files with root privileges. This could expose secrets, compromise the host, disrupt workloads, and potentially affect other tenants. Incus versions before 7.3.0 are affected.
Executive priority
Treat this as an immediate patching priority for affected multi-user or multi-tenant Incus systems. Root-level host file access can turn limited platform access into full host compromise. Accelerate version verification and access review, while avoiding claims of an ongoing campaign because active exploitation is not established.
Technical view
A malicious image can replace metadata.yaml with a symbolic link to an arbitrary host path. Incus then follows that link during metadata API operations, enabling root-level host file reads or writes. Earlier confinement and symbolic-link protections covered exec-output and templates/ but omitted metadata.yaml. Version 7.3.0 corrects the omission.
Likely exposure
Exposure requires Incus earlier than 7.3.0 and an authenticated user able to introduce or use a malicious image and access the instance metadata API. Shared or multi-tenant environments with less-trusted Incus users have the greatest risk. The supplied sources do not identify specific default configurations or internet-exposure requirements.
Exploitation context
The CVSS 3.1 score is 9.9, reflecting low-complexity, network-reachable exploitation by a low-privileged authenticated user without user interaction. Successful abuse crosses a security boundary and can affect confidentiality, integrity, and availability. The supplied bundle says this CVE is not in KEV and provides no evidence of active exploitation.
Researcher notes
The flaw is classified as CWE-73 and concerns insufficient confinement of a filename or path. The important regression detail is that prior protections using Lstat rejection and os.OpenRoot covered related paths but excluded metadata.yaml. The supplied evidence does not describe public proof-of-concept availability, observed attacks, or indicators of compromise.
Mitigation direction
- Upgrade Incus to version 7.3.0 or later.
- Prioritize shared environments containing untrusted or delegated Incus users.
- Restrict image-management and instance-metadata access until upgrades are complete.
- Check the vendor advisory for any additional operational guidance.
Validation and detection
- Inventory Incus hosts and confirm every installed version is 7.3.0 or later.
- Identify users permitted to import images or access instance metadata.
- Review relevant activity for unexpected metadata operations involving metadata.yaml.
- Check sensitive host files for unexplained reads, modifications, or integrity changes.
Public sources used
Generated from the cited source records. This long-tail analysis has not been individually reviewed by a named human.
Conservative CVE-to-ATT&CK context
These mappings and lookup hints may be relevant to the vulnerability behavior, CWE, affected product, or exposure path. Glexia-inferred context is not an official MITRE, ATT&CK, CWE, or CVE Program mapping.
ATT&CK lookup starting points
Use these exact CWE pages and searches to review the Glexia ATT&CK library from this CVE's weakness and description context.
CWE-73: File access and web shell behavior lookup
File traversal and upload weaknesses can lead teams to review file, web shell, execution, and collection telemetry. Open the exact CWE lookup page first, then review the ATT&CK searches from that MITRE weakness context. This is a Glexia lookup hint, not an official ATT&CK mapping.
Open ATT&CK lookupFile access behavior lookup
The CVE wording references file access or upload behavior, so file telemetry and web shell review may help. This is a Glexia inferred lookup path, not an official MITRE, ATT&CK, or CVE Program mapping.
Open ATT&CK lookupContainer behavior lookup
The affected technology mentions containers, so container-specific ATT&CK technique review may help. This is a Glexia inferred lookup path, not an official MITRE, ATT&CK, or CVE Program mapping.
Open ATT&CK lookupCVE-2026-63343 mapping review
Open the CVE-to-ATT&CK bridge for reviewed, inferred, or future official mappings tied to this CVE.
Open ATT&CK lookup- Severity
- Critical
- CVSS
- 9.9 (3.1)
- Known Exploited
- No
- Published
Vector: CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:C/C:H/I:H/A:H
CNA and ADP enrichment extracted from CVE v5
These fields come from the CVE record and ADP containers, not from Glexia's Take. They preserve time-varying source decisions such as CISA SSVC, KEV status, CVSS metrics, and provider references.
SSVC decision data
CVSS vector scores
1 official scoreWe collect every scored CVSS vector available in the official CNA and ADP containers. When more than one version is present, the table keeps the source vectors side by side instead of collapsing them into the highest score.
CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:C/C:H/I:H/A:H3.16GitHub_MVulnerability scoring details
Base CVSS 3.1 score
9.9CriticalVector: CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:C/C:H/I:H/A:H
Vulnerability timeline
Timeline events are normalized from CVE metadata, CNA source timelines, ADP timelines, and KEV metadata when present.
- CVE reservedCVE Program
The CVE ID was reserved by the assigning CNA.
- CVE publishedCVE Program
The CVE record was published.
- CVE updatedCVE Program
The CVE record metadata indicates this as the latest update time.
ADP provider summaries
Source materials
- CVE List V5 sourceCVE List V5
- https://github.com/lxc/incus/security/advisories/GHSA-fmjx-5j3g-997pCVE reference, GitHub_M · x_refsource_CONFIRM
Products and packages named in the record
CWE details
CWE links open Glexia weakness intelligence pages with official CWE context, developer remediation guidance, and related CVE mappings.
External Control of File Name or Path
External Control of File Name or Path represents a recurring weakness pattern that can create exploitable paths when design, validation, or implementation controls are missing.