Description
Insecure Temporary File vulnerability in Mix deps.partition in Elixir allows a local user to execute code as another user via a swapped partition config file. Partitioned dependency compilation passes the project configuration to each partition VM through a file in a fixed-name directory under the shared system temporary directory, and the partition trusts what it reads back. Another local user on the same host can exploit this during a mix deps.compile run that uses partitioned compilation.

Mix.Tasks.Deps.Partition.server/4 in lib/mix/lib/mix/tasks/deps.partition.ex creates the directory with File.mkdir_p/1, which accepts an existing directory without checking its owner, so a user who created it first can replace the file before client/0 reads it.

This issue affects mix: from 1.20.0-rc.4 before 1.20.5.
Published: 2026-10-30
Score: 5.4 Medium
EPSS: < 1% Very Low
KEV: No
Impact: n/a
Action: n/a
AI Analysis

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Remediation

Vendor Workaround

On a multi-user host, set TMPDIR to a private per-user directory with mode 0700 before running Mix, so that System.tmp_dir/0 resolves to a location other users cannot pre-create or read. Alternatively, keep partitioned compilation disabled by leaving MIX_OS_DEPS_COMPILE_PARTITION_COUNT unset or at 1, which keeps the configuration inside the parent process.

Tracking

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Advisories

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History

Fri, 30 Oct 2026 09:15:00 +0000

Type Values Removed Values Added
Description Insecure Temporary File vulnerability in Mix deps.partition in Elixir allows a local user to execute code as another user via a swapped partition config file. Partitioned dependency compilation passes the project configuration to each partition VM through a file in a fixed-name directory under the shared system temporary directory, and the partition trusts what it reads back. Another local user on the same host can exploit this during a mix deps.compile run that uses partitioned compilation. Mix.Tasks.Deps.Partition.server/4 in lib/mix/lib/mix/tasks/deps.partition.ex creates the directory with File.mkdir_p/1, which accepts an existing directory without checking its owner, so a user who created it first can replace the file before client/0 reads it. This issue affects mix: from 1.20.0-rc.4 before 1.20.5.
Title Insecure temporary file in mix deps.partition lets a local user execute code in another user's dependency build
First Time appeared Elixir-lang
Elixir-lang elixir
Weaknesses CWE-377
CPEs cpe:2.3:a:elixir-lang:elixir:*:*:*:*:*:*:*:*
Vendors & Products Elixir-lang
Elixir-lang elixir
References
Metrics cvssV4_0

{'score': 5.4, 'vector': 'CVSS:4.0/AV:L/AC:L/AT:P/PR:L/UI:P/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N'}


Subscriptions

Elixir-lang Elixir
cve-icon MITRE

Status: PUBLISHED

Assigner: EEF

Published:

Updated: 2026-10-30T16:50:46.465Z

Reserved: 2026-10-14T21:45:01.541Z

Link: CVE-2026-97209

cve-icon Vulnrichment

No data.

cve-icon NVD

Status : Received

Published: 2026-10-30T09:17:15.640

Modified: 2026-10-30T09:17:15.640

Link: CVE-2026-97209

cve-icon Redhat

No data.

cve-icon OpenCVE Enrichment

Updated: 2026-10-30T11:15:11Z

Weaknesses