VulnerabilityPublished 22 Oct 2026Updated 29 Oct 2026

CVE-2026-113716: virtualenv · Builtin creation follows linked environment directories

Affects pdmSource GCVE Database

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Authoritative record:CVE-2026-113716· Medium 4.5

Not known to be exploited · CVSS 4.5 Medium : upgrade to 2.29.3 or 2.9.3_2 when convenient.

Data as of 30 Oct 2026, 07:30 UTC

CVSS 3.1 base score

4.5Medium

How severe the flaw is on the 0–10 CVSS scale.

Patch: Available – fixed in 2.29.3, 2.9.3_2

CVSS:3.1/AV:L/AC:H/PR:L/UI:N/S:U/C:L/I:L/A:L

Attack Vector: Local
Attack Complexity: High
Privileges Required: Low
User Interaction: None
Scope: Unchanged
Confidentiality: Low
Integrity: Low
Availability: Low

Bold values are the worst case: easiest to exploit or largest impact.

Attack Vector: Local: The vulnerable component is not bound to the network stack and the attacker’s path is via read/write/execute capabilities. Either: the attacker exploits the vulnerability by accessing the target system locally (e.g., keyboard, console), or remotely (e.g., SSH); or the attacker relies on User Interaction by another person to perform actions required to exploit the vulnerability (e.g., tricking a legitimate user into opening a malicious document).
Attack Complexity: High: A successful attack depends on conditions beyond the attacker's control. That is, a successful attack cannot be accomplished at will, but requires the attacker to invest in some measurable amount of effort in preparation or execution against the vulnerable component before a successful attack can be expected. For example, a successful attack may require an attacker to: gather knowledge about the environment in which the vulnerable target/component exists; prepare the target environment to improve exploit reliability; or inject themselves into the logical network path between the target and the resource requested by the victim in order to read and/or modify network communications (e.g., a man in the middle attack).
Privileges Required: Low: The attacker is authorized with (i.e., requires) privileges that provide basic user capabilities that could normally affect only settings and files owned by a user. Alternatively, an attacker with Low privileges may have the ability to cause an impact only to non-sensitive resources.
User Interaction: None: The vulnerable system can be exploited without any interaction from any user.
Scope: Unchanged: An exploited vulnerability can only affect resources managed by the same security authority. In this case, the vulnerable component and the impacted component are either the same, or both are managed by the same security authority.
Confidentiality: Low: There is some loss of confidentiality. Access to some restricted information is obtained, but the attacker does not have control over what information is obtained, or the amount or kind of loss is limited. The information disclosure does not cause a direct, serious loss to the impacted component.
Integrity: Low: Modification of data is possible, but the attacker does not have control over the consequence of a modification, or the amount of modification is limited. The data modification does not have a direct, serious impact on the impacted component.
Availability: Low: Performance is reduced or there are interruptions in resource availability. Even if repeated exploitation of the vulnerability is possible, the attacker does not have the ability to completely deny service to legitimate users. The resources in the impacted component are either partially available all of the time, or fully available only some of the time, but overall there is no direct, serious consequence to the impacted component.

Definitions: FIRST CVSS v3.1 specification.

Exploitation evidence

Disclosed: evidence found.
CVE published 20 Oct 2026
Detectable: no evidence on record.
No public nuclei template indexed
Weaponized: no evidence on record.
No public exploit code indexed in Metasploit or Exploit-DB
Exploited in the wildExploited: no evidence on record.
Not in CISA KEV and no source reports exploitation
Observed by OffSeq MirageSeen by Mirage: no evidence on record.
No attack traffic recorded by OffSeq Mirage sensors

A missing step is not evidence of safety. Sources: cve.org (opens in a new tab), the Metasploit, Exploit-DB and nuclei-templates index as of 29 Oct 2026.

Disclosed: The CVE record is public on cve.org. Its publication is t = 0.
Detectable: A public nuclei template can find exposed instances, for defenders and attackers alike.
Weaponized: A Metasploit exploit module or Exploit-DB entry exists (Metasploit scanner modules do not count), or CISA SSVC or the CVSS exploit maturity reports a public proof of concept.
Exploited in the wild: CISA KEV lists it, CISA SSVC rates exploitation active, or a source reports attacks.
Observed by OffSeq Mirage: OffSeq Mirage honeypot sensors recorded attack traffic for this CVE, or found exposed hosts without attack traffic.

Moments are spaced evenly, not to scale; a dashed line marks a gap of six months or more. Deltas count from t = 0. Sources that give only a date (CISA KEV, Exploit-DB, or a time of exactly 00:00Z) read “same day” rather than hours. Metasploit modules carry the flaw’s disclosure date, not their release date, and nuclei templates carry no date, so both appear above but not on the timeline.

What to do

Upgrade pdm to 2.29.3 or 2.9.3_2.

Affected software

Product	Affected	Fixed in
Homebrewpdm`pkg:brew/pdm`Other threats	Affected >=2.0.0 <2.9.3_2 >=2.12.3 <2.29.3	Fixed in 2.9.3_2 2.29.3

Check your own hosts for these packages with threat-finder (opens in a new tab), our free open-source scanner.

Description

## Summary The builtin creator accepts existing directory symlinks through ensure_dir() and writes environment files through those directories. This permits writes outside the requested destination. Anthropic's OSS Scanner reported this as `ANT-2026-MUFJEG11` in `virtualenv-20261015-005`, received on 15 October 2026. ## Affected area Directory preparation before environment files are created. ## Attacker-controlled input Another account must be able to prepare linked entries below the chosen destination before creation. The invoking user must have access to the linked destination. This does not require write access to the target itself under the other account. ## Affected code The relevant 21.14.8 source is in [builtin creator](https://github.com/pypa/virtualenv/blob/a795ab116356afde11039cf2763d77e8a06da738/src/virtualenv/create/via_global_ref/builtin/via_global_self_do.py), [ensure_dir()](https://github.com/pypa/virtualenv/blob/a795ab116356afde11039cf2763d77e8a06da738/src/virtualenv/util/path/_sync.py). ## Mechanism The builtin creator calls `ensure_dir()` for `bin`, `lib`, and package directories. `ensure_dir()` accepts an existing symlink to a directory because `exists()` follows it. Interpreter creation, seed installation, and activation-script generation then write through that parent link. A final-file check cannot prevent a write through a linked parent. `--clear` removes the planted tree first; ordinary creation over a prepared destination reaches it. ## Reproduction and evidence The scanner's project tree contains `venv/bin -> ../../.local/bin` and a `.pth` file in the environment's package tree. With the user's initially empty `~/.local/bin` first on `PATH`, `virtualenv venv` exited successfully and wrote `python*`, `pip*`, and `activate*` into `~/.local/bin`. The marker was absent immediately after creation; a later `pip --version` on the user's `PATH` loaded the seeded environment and the planted `.pth` code wrote the marker. A second case began with the `bin` link resolving inside the environment; replacement of a planted package link during seeding changed where it resolved, and writes again reached `~/.local/bin`. The attacker must prepare entries in an existing destination. The `.pth` content is already attacker-controlled and would run if the user used that environment directly; the added effect is creation-time writing or replacement outside the requested tree and an executable on the user's `PATH` pointing at it. The scanner traces this default builtin path to 20.0.0b1. [PR #3429](https://github.com/pypa/virtualenv/pull/3429) replaces linked directory components before creation. Concurrent parent replacement remains a separate case. ## Attack sequence ```mermaid sequenceDiagram participant A as Prepared destination participant V as Builtin creator participant L as venv/bin symlink participant H as ~/.local/bin participant U as User A->>L: point to ../../.local/bin V->>L: ensure_dir accepts existing directory link V->>H: write python, pip and activate files through link V-->>U: creation reports success U->>H: run pip found on PATH H->>A: interpreter loads planted .pth A-->>U: marker created ``` ## Reproducer files The following files are from the scanner report for `ANT-2026-MUFJEG11`. They were tested against commit `a857a7823c73` in the scanner image. The `repro` entrypoint expects companion files under `/tmp/repro.d`; cases that change user IDs need a disposable root-capable container. The last output line is `BUG` when the reported behavior occurs. These files are included as evidence and were not rerun for this advisory update. **`repro`** ```text #!/usr/bin/env python3 import os import shutil import subprocess import sys from pathlib import Path WORK = Path("/tmp/planted-bin-link") shutil.rmtree(WORK, ignore_errors=True) def user_creates_venv_in_checkout_then_runs_pip(home, make_checkout): local_bin = home / ".local/bin" user_env = {"HOME": str(home), "PATH": f"{local_bin}:{os.environ['PATH']}"} local_bin_before = set(os.listdir(local_bin)) payload_marker = home / "PWNED" # the attacker's checkout arrives at ~/project subprocess.run([sys.executable, f"/tmp/repro.d/{make_checkout}", home / "project"], check=True) venv = home / "project/venv" print(f"CONTROL venv/bin before the run resolves to {os.path.realpath(venv / 'bin')}") # default options; the flag only keeps the run off the network subprocess.run(["virtualenv", "--no-periodic-update", "--quiet", "venv"], cwd=home / "project", env=user_env, check=True) written = sorted(set(os.listdir(local_bin)) - local_bin_before) payload_ran_at_creation = payload_marker.exists() print(f"OBSERVED venv/bin after the run resolves to {os.path.realpath(venv / 'bin')}") print(f"OBSERVED virtualenv wrote to {local_bin}: {written}") print(f"OBSERVED ~/PWNED exists after virtualenv: {payload_ran_at_creation}") # lat

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