Build-user privilege escalation via descriptor smuggling
Published Jun 27, 2025 · Updated Jun 27, 2025
Build isolation bypass in Nix allows local users to gain build-user privileges by submitting untrusted derivations. A fixed-output derivation can pass an output-directory file descriptor over a shared abstract Unix socket, retaining access after sandbox teardown. Local build access and a cooperating process are required; the direct result is execution as a nixbld account, not root.
Summary
What happened
Build isolation bypass in Nix allows local users to gain build-user privileges by submitting untrusted derivations. A fixed-output derivation can pass an output-directory file descriptor over a shared abstract Unix socket, retaining access after sandbox teardown. Local build access and a cooperating process are required; the direct result is execution as a nixbld account, not root.
The record
- CVE
- CVE-2025-46416
- Published
- Jun 27, 2025
- Updated
- Jun 27, 2025
- Vendor
- NixOS
- Product
- Nix
- Classifications
- CWE-282, T1068
- Attack vector
- local
- Privileges
- unauthenticated
Timeline
How it unfolded
- Jun 27, 2025CVE publishedPublication date reported by the CVE source.
- Jun 27, 2025Record updatedLatest update available in the CVE record.
Exploitability
Present is not the same as exploitable
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Is a vulnerable build present?
Compare these published version ranges with your installed build and any vendor patches.
- Affected versionversion=0 <=2.24.15
- Affected versionversion=2.25.0 <=2.26.4
- Affected versionversion=2.27.0 <=2.28.4
- Affected versionversion=2.29.0 <=2.29.1
What conditions does exploitation require?
What is affected?
Published CVSS scores
CVSS describes severity. EPSS estimates exploitation probability.
Attacks
What attackers are doing with it
Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.
Weakness, pattern, technique
Public exploit references
- NixOS privilege-escalation proof of conceptfunctional · demonstrated
Labels summarize the accepted research assessment. They do not indicate a test against your environment.
Technologies
Your stack
See the directory against your own environment.
Your stack
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