7.6

CVSS Score

3.1

-

CVSS Score

Basic Information

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CVE-2026-32606

CVE-2026-32606: IncusOS has a LUKS encryption bypass due to insufficient TPM policy

IncusOS is an immutable OS image dedicated to running Incus. Prior to 202603142010, the default configuration of systemd-cryptenroll as used by IncusOS through mkosi allows for an attacker with physical access to the machine to access the encrypted data without requiring any interaction by the system's owner or any tampering of Secure Boot state or kernel (UKI) boot image. That's because in this configuration, the LUKS key is made available by the TPM so long as the system has the expected PCR7 value and the PCR11 policy matches. That default PCR11 policy importantly allows for the TPM to release the key to the booted system rather than just from the initrd part of the signed kernel image (UKI). The attack relies on the attacker being able to substitute the original encrypted root partition for one that they control. By doing so, the system will prompt for a recovery key on boot, which the attacker has defined and can provide, before booting the system using the attacker's root partition rather than the system's original one. The attacker only needs to put a systemd unit starting on system boot within their root partition to have the system run that logic on boot. That unit will then run in an environment where the TPM will allow for the retrieval of the encryption key of the real root disk, allowing the attacker to steal the LUKS volume key (immutable master key) and then use it against the real root disk, altering it or getting data out before putting the disk back the way it was and returning the system without a trace of this attack having happened. This is all possible because the system will have still booted with Secure Boot enabled, will have measured and ran the expected bootloader and kernel image (UKI). The initrd selects the root disk based on GPT partition identifiers making it possible to easily substitute the real root disk for an attacker controlled one. This doesn't lead to any change in the TPM state and therefore allows for retrieval of the LUKS key by the attacker through a boot time systemd unit on their alternative root partition. IncusOS version 202603142010 (2026/03/14 20:10 UTC) includes the new PCR15 logic and will automatically update the TPM policy on boot. Anyone suspecting that their system may have been physically accessed while shut down should perform a full system wipe and reinstallation as only that will rotate the LUKS volume key and prevent subsequent access to the encrypted data should the system have been previously compromised. There are no known workarounds other than updating to a version with corrected logic which will automatically rebind the LUKS keys to the new set of TPM registers and prevent this from being exploited.

(GitHub Advisory)

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CVE-2026-32606

CVE-2026-32606:

7.6

CVSS Score

3.1

-

CVSS Score

Basic Information

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Technical Details

Package Name	Ecosystem	Vulnerable Versions	First Patched Version
github.com/lxc/incus-os/incus-osd	go	< 0.0.0-20260313012803-e3b35f230d23	0.0.0-20260313012803-e3b35f230d23

Technical Details

Vulnerability Intelligence
Miggo AI

Root Cause Analysis

The vulnerability is a logical flaw in the TPM policy for LUKS disk encryption in IncusOS, identified as GHSA-wj2j-qwcf-cfcc. The system was configured to bind the LUKS encryption key to TPM PCRs 7 and 11 (and 4 if not using Secure Boot). This policy was insufficient because it allowed the TPM to release the encryption key even after the initial boot phase (initrd) had completed.

An attacker with physical access could exploit this by substituting the real root partition with a malicious one. The system would still boot with the correct Secure Boot and TPM state up to the end of the initrd, as the signed kernel image (UKI) was not modified. The attacker's malicious OS would then run, and because the TPM state was still considered 'good' under the vulnerable policy, a script on the attacker's OS could request the LUKS key for the original (now detached) root partition from the TPM, thus bypassing the disk encryption.

The fix, implemented in commit e3b35f230d23443d27752eac27ebb2b22c957b75, was to add a binding to PCR15. PCR15 is extended by systemd when the root LUKS volume is unlocked in the initrd. By binding the key to an uninitialized (all zeros) value of PCR15, the key can only be released by the TPM during the initrd phase. Once the root volume is unlocked, PCR15's value changes, and the TPM will no longer release the key. This prevents the attacker's OS, which runs after the initrd phase, from accessing the key.

The identified vulnerable functions are those that were responsible for creating the original, insecure TPM binding by calling systemd-cryptenroll without including the PCR15 binding. These functions were modified in the patch to include the +15:sha256=00...0 argument in the systemd-cryptenroll command. The main.startup function is also included as it's the high-level entry point that orchestrates this configuration on boot and is where the check for the vulnerable configuration is now performed.

Vulnerable functions

main.startup

incus-osd/cmd/incus-osd/main.go

This is the main entry point function that runs on system startup. The patch adds a check to this function to verify if the LUKS volumes are bound to PCR15. If they are not, it calls `secureboot.HandleSecureBootKeyChange` to apply the corrected TPM policy. On a vulnerable system, this function would proceed without the secure PCR15 binding, leaving the system in a state that can be exploited.

secureboot.HandleSecureBootKeyChange

incus-osd/internal/secureboot/secureboot.go

This function is responsible for setting the TPM PCR bindings for LUKS volumes when a Secure Boot key change is handled. The original implementation was vulnerable because it only bound to PCR7 (and PCR4), which was insufficient to prevent the attack. The patch modifies this function to add a binding to an uninitialized PCR15, which ensures the LUKS key can only be released by the TPM during the initrd phase.

secureboot.UpdatePCR4Binding

incus-osd/internal/secureboot/secureboot.go

Similar to `HandleSecureBootKeyChange`, this function updates the PCR4 binding but was also creating an insecure TPM policy by not including PCR15. The patch corrects this by adding the PCR15 binding to the `systemd-cryptenroll` command.

secureboot.ForceUpdatePCRBindings

incus-osd/internal/secureboot/pcrs.go

This function is used to forcibly update the PCR bindings. The original implementation created a vulnerable configuration by omitting the PCR15 binding, which is corrected in the patch.

secureboot.appendEFIVarUpdate

incus-osd/internal/secureboot/efi_vars.go

This function, which handles updates to EFI variables, also updates the LUKS volume bindings. It was vulnerable as it called `systemd-cryptenroll` without the necessary PCR15 binding, a flaw that the patch rectifies.

storage.LUKSBoundToPCR

incus-osd/internal/storage/luks.go

This new function was added as part of the fix to check if a LUKS volume is bound to a specific PCR. It is used by the `main.startup` function to detect if the system has the vulnerable configuration and needs to be updated. While not vulnerable itself, it is a key component of the mitigation logic.

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WAF Rule

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Reasoning

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