incus: Improper Link Resolution Before File Access
CVE-2026-63125 is a critical-severity improper link resolution before file access vulnerability in incus from Lxc, with a CVSS 3.1 base score of 9.9 out of 10. It can be exploited remotely over the network by an attacker with a low-privileged account, without any action from a user. Affected incus versions: < 7.3.0. The record does not name a fixed version, so check the vendor advisory. There is no confirmed exploitation so far. EPSS estimates a 0.66% chance of exploitation within 30 days, higher than 52% of scored CVEs.
Critical severity: a successful attack would have severe impact.
What to do
- Check which version of incus you run against the affected versions below, and install the vendor's latest release.
- Read the advisory on github.com for workarounds and exact fixed builds.
Affected products and versions
Version data comes from the organisation that assigned the CVE. Confirm against the vendor advisory before deciding you are unaffected.
How the severity score breaks down
- Attack vector
- NetworkCan be exploited remotely over a network, including the internet.
- Attack complexity
- LowNo special conditions are needed; the attack works reliably.
- Privileges required
- LowA basic user account is enough.
- User interaction
- NoneNo action by a victim is required.
- Scope
- ChangedThe attack can reach beyond the vulnerable component into other systems.
- Confidentiality
- HighAll data handled by the component can be read.
- Integrity
- HighData or code can be modified at will.
- Availability
- HighThe component can be taken down completely.
Vector: CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:C/C:H/I:H/A:H. Scored by CNA (github.com).
Official description
Incus is a system container and virtual machine manager. Prior to version 7.3.0, an unprivileged, project-confined Incus user (a non-admin TLS/RBAC identity with `can_create_images` and `can_create_instances`) can execute arbitrary code as root on the host. A crafted image ships `backup.yaml` as a symlink to a host file. When the root daemon writes the instance's backup file, it follows the symlink. Version 7.3.0 patches the issue.
Source: the CVE record as published by its numbering authority, via NVD and CVE.org.
The underlying weakness: Improper Link Resolution Before File Access
The product attempts to access a file based on the filename, but it does not properly prevent that filename from identifying a link or shortcut that resolves to an unintended resource.
How developers prevent this class of flaw
- Follow the principle of least privilege when assigning access rights to entities in a software system. Denying access to a file can prevent an attacker from replacing that file with a link to a sensitive file. Ensure good compartmentalization in the system to provide protected areas that can be trusted.
More Improper Link Resolution Before File Access vulnerabilities (CWE-59)
Timeline
- CVE record published.
- CISA published its SSVC assessment (exploitation: poc, automatable: no, technical impact: total).
- Record last changed materially (score, affected products, status or references).
References
Other vulnerabilities in incus
- 9.9 Critical severity
- 7.7 High severity
- 9.9 Critical severity
- 7.1 High severity
- 8.5 High severity
- 7.1 High severity
Recent Improper Link Resolution Before File Access vulnerabilities
- 7.5 High severity
- 9.3 Critical severity
- 8.4 High severity
- 7.1 High severity
- 7.8 High severity
- 7.5 High severity
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