CVE-2026-34177: LXD: VM lowlevel restriction bypass via raw.apparmor and raw.qemu.conf

Should you act?

Critical, preconditions apply

Severe if exploited, but exploitation needs conditions that may not apply to you. This signal is computed from CISA KEV, EPSS and CVSS data; it is not an editorial verdict.

• Not in CISA KEV, but CISA’s SSVC assessment records a public proof-of-concept, so attack code exists.
• EPSS 0.6%, percentile 49: FIRST’s model estimates a 0.6% chance of exploitation activity in the next 30 days, higher than 49% of all scored CVEs (low). EPSS is a probability, not a verdict.
• Needs an account (high (admin)). Exposure depends on who can log in.
• Only applies if your dependency tree includes github.com/canonical/lxd (Go) >= 0.0.0-20210305023314-538ac3df036e, <= 0.0.0-20260226085519-736f34afb267, no fixed version listed. Check your lockfile, including transitive dependencies.

What it is

Canonical LXD versions 4.12 through 6.7 contain an incomplete denylist in isVMLowLevelOptionForbidden (lxd/project/limits/permissions.go), which omits raw.apparmor and raw.qemu.conf from the set of keys blocked under the restricted.virtual-machines.lowlevel=block project restriction. A remote attacker with canedit permission on a VM instance in a restricted project can inject an AppArmor rule and a QEMU chardev configuration that bridges the LXD Unix socket into the guest VM, enabling privilege escalation to LXD cluster administrator and subsequently to host root.

From the GitHub advisory

Summary

The isVMLowLevelOptionForbidden function in lxd/project/limits/permissions.go is missing raw.apparmor and raw.qemu.conf from its hardcoded forbidden list. A user with canedit permission on a VM instance in a restricted project can combine these two omissions to bridge the LXD unix socket into the guest VM and gain full cluster administrator access. This bypasses the restricted.virtual-machines.lowlevel=block project restriction, which is the security control specifically designed to prevent raw config injection.

Details

Affected code

The enforcement point for VM lowlevel restrictions is isVMLowLevelOptionForbidden at lxd/project/limits/permissions.go:924-926:

Weakness type: CWE-184.

Product: github.com/canonical/lxd (Go) · Assigned by: canonical · Published: 2026-04-09

Affected and fixed versions

Severity scores

• Attack vector: network (remotely reachable)
• Attack complexity: low
• Privileges required: high (admin)
• User interaction: none
• Scope: changed (can affect other components)

CVSS measures how bad a flaw is if exploited, not how likely exploitation is. Read it next to the exploitation data below.

Exploitation and urgency

• CISA KEV: not listed (no confirmed in-the-wild exploitation known to CISA).
• CISA SSVC assessment: exploitation poc, automatable no, technical impact total.
• FIRST EPSS (model of 2026-10-21): 0.61% probability of exploitation activity in the next 30 days; percentile 49.

Timeline

• 2026-04-09 — CVE record last updated
• 2026-04-09 — CVE record published by canonical
• 2026-04-10 — GitHub-reviewed advisory GHSA-fm2x-c5qw-4h6f published (critical)

Sources and references

Original sources first. Version and fix details should always be confirmed against the vendor or project advisory.

Vendor and project advisories, patches

1. VM lowlevel restriction bypass via raw.apparmor and raw.qemu.conf github.com
2. lxd: Prevent use of raw.apparmor and raw.qemu.conf when low level options are blocked github.com

Vulnerability records

1. GitHub Advisory GHSA-fm2x-c5qw-4h6f github.com
2. CVE.org record CVE-2026-34177 cve.org
3. NVD entry CVE-2026-34177 nvd.nist.gov

Critical Go advisories · Today’s Security Digest