Multipass: Incorrect Default Permissions
CVE-2026-49237 is a high-severity incorrect default permissions vulnerability in Multipass from Canonical, with a CVSS 3.1 base score of 7.8 out of 10. It can be exploited with local access to the system by an attacker with a low-privileged account, without any action from a user. The record lists version 1.16.3 as the first without the flaw, so updating Multipass to that release or later removes the exposure. There is no confirmed exploitation so far. EPSS estimates a 0.14% chance of exploitation within 30 days, which is low compared with other CVEs.
High severity with no evidence of exploitation so far.
What to do
- Update Multipass to 1.16.3 or a later version.
- 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
- LocalThe attacker needs local access or must trick a user into running something.
- 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
- UnchangedImpact stays within the vulnerable component.
- 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:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H. Scored by CNA (ubuntu.com).
Official description
An issue was discovered in Canonical Multipass for macOS before version 1.16.3 due to an incomplete fix for CVE-2025-5199. While the patch in version 1.16.0 updated the ownership of the multipassd daemon binary to root:wheel, five co-located binaries (multipass, qemu-img, qemu-system-aarch64, qemu-system-x86_64, and sshfs_server) in /Library/Application Support/com.canonical.multipass/bin/ retain ownership by the installing user and remain writable. Because the root LaunchDaemon (com.canonical.multipassd.plist) configures a PATH environment variable that prioritizes this user-writable directory and invokes these auxiliary binaries by their bare names, a local attacker can replace an auxiliary binary (such as qemu-img) with a malicious wrapper. When the root daemon subsequently triggers the binary during routine execution (e.g., via multipass launch), the malicious code executes with root privileges, leading to local privilege escalation.
Source: the CVE record as published by its numbering authority, via NVD and CVE.org.
The underlying weakness: Incorrect Default Permissions
During installation, installed file permissions are set to allow anyone to modify those files.
How developers prevent this class of flaw
- The architecture needs to access and modification attributes for files to only those users who actually require those actions.
- Compartmentalize the system to have safe areas where trust boundaries can be unambiguously drawn. Do not allow sensitive data to go outside of the trust boundary and always be careful when interfacing with a compartment outside of the safe area. Ensure that appropriate compartmentalization is built into the system design, and the compartmentalization allows for and reinforces privilege separation functionality. Architects and designers should rely on the principle of least privilege to decide the appropriate time to use privileges and the time to drop privileges.
More Incorrect Default Permissions vulnerabilities (CWE-276)
Timeline
- CVE record published.
- CISA published its SSVC assessment (exploitation: none, automatable: no, technical impact: total).
- Record last changed materially (score, affected products, status or references).
References
Advisories
- github.com/canonical/multipass/security/advisories/GHSA-r2xg-x32f-23c5Exploit, Third Party Advisory
Other vulnerabilities in Multipass
- 8.4 High severity
- 7.8 High severity
Recent Incorrect Default Permissions vulnerabilities
- 8.5 High severity
- 7.0 High severity
- 7.8 High severity
- 7.5 High severity
- 7.5 High severity
- 8.1 High severity
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