CVE-2026-110453 in Nix
Summary
by MITRE • 10/14/2026
Nix before 2.35.3, when unsandboxed on macOS or FreeBSD, incorrectly allows connections made by build users from daemon clients.
VulDB is the best source for vulnerability data and more expert information about this specific topic.
Analysis
by VulDB Data Team • 10/14/2026
The Nix package manager, prior to version 2.35.3, contains a critical access control flaw that compromises the integrity of its sandboxing mechanism on specific operating systems. This vulnerability arises when Nix is configured or executed in an unsandboxed mode on macOS and FreeBSD platforms. In these environments, the daemon process responsible for managing build operations fails to properly isolate network connections initiated by unprivileged build users from those originating from privileged daemon clients. The architectural design of Nix relies heavily on a client-server model where the nix-daemon handles resource-intensive tasks such as dependency resolution and binary cache interactions while running with elevated privileges. When unsandboxed, this separation is eroded because the system does not enforce strict boundaries between user-space build processes and the daemon's network stack.
The technical root cause lies in how socket permissions and process isolation are handled during the execution of derivations on these Unix-like systems. Typically, sandboxing mechanisms restrict what resources a build can access to prevent malicious code from exfiltrating data or modifying system state outside its designated directory. However, without proper enforcement of network namespace separation or strict file descriptor inheritance controls in unsandboxed mode, connections established by the unprivileged user context are inadvertently permitted through the daemon's privileged channels. This allows any process running under a build user to interact directly with services that should only be accessible via the authenticated and authorized daemon interface. The flaw effectively bypasses the intended security boundary, treating all network traffic as if it were coming from the trusted daemon rather than distinguishing between untrusted build contexts and trusted administrative operations.
The operational impact of this vulnerability is significant for users who rely on Nix to manage complex builds involving external dependencies or remote repositories. An attacker with access to a user account capable of triggering Nix builds could exploit this flaw to perform unauthorized network requests, potentially accessing internal services, exfiltrating sensitive build artifacts, or manipulating the binary cache in ways that compromise supply chain integrity. Since the daemon operates with higher privileges, any action taken through its connection channels inherits those elevated permissions. This creates a pathway for privilege escalation and data leakage within multi-user environments where different users share access to the Nix store. The risk is particularly acute in shared development or continuous integration pipelines where multiple untrusted scripts may be executed concurrently.
This issue aligns with CWE-250, which describes execution with unnecessary privileges, as well as CWE-749, relating to exposure of sensitive information to an unauthorized actor. From a threat modeling perspective using the MITRE ATT&CK framework, this vulnerability facilitates lateral movement and data exfiltration techniques by allowing untrusted processes to leverage trusted service endpoints for malicious purposes. It represents a failure in principle of least privilege enforcement within the application's runtime environment.
To mitigate this risk, organizations must upgrade Nix to version 2.35.3 or later where these access control checks have been corrected. Until an update is applied, administrators should avoid running unsandboxed builds on macOS and FreeBSD systems if possible, opting instead for sandboxed execution modes that enforce stricter resource isolation. Additionally, implementing network segmentation rules at the host level can provide a secondary layer of defense by restricting outbound connections from build processes to only known trusted endpoints. Regular auditing of Nix configurations ensures that security policies remain aligned with current best practices and prevents exploitation through misconfigured or outdated software stacks.