chore(deps): update dependency python-dotenv to v1.2.2 [security]

renovate commented

2026-06-27 19:22:53 -07:00

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This PR contains the following updates:

Package	Update	Change
python-dotenv	minor	`==1.0.0` → `==1.2.2`

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Some dependencies could not be looked up. Check the Dependency Dashboard for more information.

python-dotenv: Symlink following in set_key allows arbitrary file overwrite via cross-device rename fallback

CVE-2026-28684 / GHSA-mf9w-mj56-hr94 / PYSEC-2026-2270

More information

Details

Summary

set_key() and unset_key() in python-dotenv follow symbolic links when rewriting .env files, allowing a local attacker to overwrite arbitrary files via a crafted symlink when a cross-device rename fallback is triggered.

Details

The rewrite() context manager in dotenv/main.py is used by both set_key() and unset_key() to safely modify .env files. It works by writing to a temporary file (created in the system's default temp directory, typically /tmp) and then using shutil.move() to replace the original file.

When the .env path is a symbolic link and the temp directory resides on a different filesystem than the target (a common configuration on Linux systems using tmpfs for /tmp), the following sequence occurs:

shutil.move() first attempts os.rename(), which fails with an OSError because atomic renames cannot cross device boundaries.
On failure, shutil.move() falls back to shutil.copy2() followed by os.unlink().
shutil.copy2() calls shutil.copyfile() with follow_symlinks=True by default.
This causes the content to be written to the symlink target rather than replacing the symlink itself.

An attacker who has write access to the directory containing a .env file can pre-place a symlink pointing to any file that the application process has write access to. When the application (or a privileged process such as a deploy script, Docker entrypoint, or CI pipeline) calls set_key() or unset_key(), the symlink target is overwritten with the new .env content.

This vulnerability does not require a race condition and is fully deterministic once the preconditions are met.

Impact

The primary impacts are to integrity and availability:

File overwrite / destruction (DoS): An attacker can cause an application or privileged process to corrupt or destroy configuration files, database configs, or other sensitive files it would not normally have access to modify.
Integrity violation: The target file's original content is replaced with .env-formatted content controlled by the attacker.
Potential privilege escalation: In scenarios where a privileged process (running as root or a service account) calls set_key(), the attacker can leverage this to write to files beyond their own access level.

The scope of impact depends on the application using python-dotenv and the privileges under which it runs.

Proof of Concept

The following script demonstrates the vulnerability. It requires /tmp and the user's home directory to reside on different devices (common on systemd-based Linux systems with tmpfs).

import os
import sys
import tempfile
from dotenv import set_key

##### Pre-condition: /tmp must be on a different device than the target directory.
tmp_dev = os.stat("/tmp").st_dev
home_dev = os.stat(os.path.expanduser("~")).st_dev
assert tmp_dev != home_dev, "Skipped: /tmp and ~ are on the same device (no cross-device move)"

with tempfile.TemporaryDirectory(dir=os.path.expanduser("~")) as workdir:
    # File an attacker wants to overwrite
    target = os.path.join(workdir, "victim_config.txt")
    with open(target, "w") as f:
        f.write("DB_PASSWORD=supersecret\n")

    # Attacker pre-places a symlink at the path the application will use as .env
    env_symlink = os.path.join(workdir, ".env")
    os.symlink(target, env_symlink)

    before = open(target).read()

    # Application writes a new key -- triggers the cross-device fallback
    set_key(env_symlink, "INJECTED", "attacker_value")

    after = open(target).read()

    print("Before:", repr(before))
    print("After: ", repr(after))
    print("Symlink target overwritten:", target)

Expected output:

Before: 'DB_PASSWORD=supersecret\n'
After:  "DB_PASSWORD=supersecret\nINJECTED='attacker_value'\n"
Symlink target overwritten: /home/user/tmp806nut2g/victim_config.txt

Remediation

The fix changes the rewrite() context manager in the following ways:

Symlinks are no longer followed by default. When the .env path is a symlink, rewrite() now resolves it to the real path before proceeding, or (by default) operates on the symlink entry itself rather than the target.
A follow_symlinks: bool = False parameter is added to set_key() and unset_key() for users who explicitly need the old behavior.
Temp files are written in the same directory as the target .env file (instead of the system temp directory), eliminating the cross-device rename condition entirely.
os.replace() is used instead of shutil.move(), providing atomic replacement without symlink-following fallback behavior.

Users are advised to upgrade to the patched version as soon as it is available on PyPI.

Timeline

Date	Event
2026-01-09	Initial report received from Giorgos Tsigourakos regarding a separate, unrelated issue also located in `rewrite()`
2026-01-10	Co-maintainer acknowledged report, requested clarification
2026-01-11	Initial report assessed as not exploitable and closed
2026-02-24	Reporter identified new, distinct cross-device symlink attack vector with deterministic exploitation
2026-02-26	Co-maintainer confirmed vulnerability and shared draft patch
2026-02-26	Reporter validated fix with monkeypatched PoC, proposed CVSS
2026-03-01	Patch merged to main
2026-03-01	Patched version released to PyPI
2026-04-20	Advisory published

Patches

Upgrade to v.1.2.2 or use the patch from 790c5c0299.patch

Severity

CVSS Score: 6.6 / 10 (Medium)
Vector String: CVSS:3.1/AV:L/AC:L/PR:L/UI:R/S:U/C:N/I:H/A:H

References

This data is provided by OSV and the GitHub Advisory Database (CC-BY 4.0).

CVE-2026-28684 / GHSA-mf9w-mj56-hr94 / PYSEC-2026-2270

More information

Details

python-dotenv reads key-value pairs from a .env file and can set them as environment variables. Prior to version 1.2.2, set_key() and unset_key() in python-dotenv follow symbolic links when rewriting .env files, allowing a local attacker to overwrite arbitrary files via a crafted symlink when a cross-device rename fallback is triggered. Users should upgrade to v.1.2.2 or, as a workaround, apply the patch manually.

Severity

CVSS Score: 6.6 / 10 (Medium)
Vector String: CVSS:3.1/AV:L/AC:L/PR:L/UI:R/S:U/C:N/I:H/A:H

References

This data is provided by OSV and the PyPI Advisory Database (CC-BY 4.0).

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This PR contains the following updates: | Package | Update | Change | |---|---|---| | [python-dotenv](https://github.com/theskumar/python-dotenv) | minor | `==1.0.0` → `==1.2.2` | --- > ⚠️ **Warning** > > Some dependencies could not be looked up. Check the [Dependency Dashboard](issues/3) for more information. --- ### python-dotenv: Symlink following in set_key allows arbitrary file overwrite via cross-device rename fallback [CVE-2026-28684](https://nvd.nist.gov/vuln/detail/CVE-2026-28684) / [GHSA-mf9w-mj56-hr94](https://github.com/advisories/GHSA-mf9w-mj56-hr94) / PYSEC-2026-2270 <details> <summary>More information</summary> #### Details ##### Summary `set_key()` and `unset_key()` in python-dotenv follow symbolic links when rewriting `.env` files, allowing a local attacker to overwrite arbitrary files via a crafted symlink when a cross-device rename fallback is triggered. ##### Details The `rewrite()` context manager in `dotenv/main.py` is used by both `set_key()` and `unset_key()` to safely modify `.env` files. It works by writing to a temporary file (created in the system's default temp directory, typically `/tmp`) and then using `shutil.move()` to replace the original file. When the `.env` path is a symbolic link and the temp directory resides on a different filesystem than the target (a common configuration on Linux systems using tmpfs for `/tmp`), the following sequence occurs: 1. `shutil.move()` first attempts `os.rename()`, which fails with an `OSError` because atomic renames cannot cross device boundaries. 2. On failure, `shutil.move()` falls back to `shutil.copy2()` followed by `os.unlink()`. 3. `shutil.copy2()` calls `shutil.copyfile()` with `follow_symlinks=True` by default. 4. This causes the content to be written to the **symlink target** rather than replacing the symlink itself. An attacker who has write access to the directory containing a `.env` file can pre-place a symlink pointing to any file that the application process has write access to. When the application (or a privileged process such as a deploy script, Docker entrypoint, or CI pipeline) calls `set_key()` or `unset_key()`, the symlink target is overwritten with the new `.env` content. This vulnerability does not require a race condition and is fully deterministic once the preconditions are met. ##### Impact The primary impacts are to **integrity** and **availability**: - **File overwrite / destruction (DoS):** An attacker can cause an application or privileged process to corrupt or destroy configuration files, database configs, or other sensitive files it would not normally have access to modify. - **Integrity violation:** The target file's original content is replaced with `.env`-formatted content controlled by the attacker. - **Potential privilege escalation:** In scenarios where a privileged process (running as root or a service account) calls `set_key()`, the attacker can leverage this to write to files beyond their own access level. The scope of impact depends on the application using python-dotenv and the privileges under which it runs. ##### Proof of Concept The following script demonstrates the vulnerability. It requires `/tmp` and the user's home directory to reside on different devices (common on systemd-based Linux systems with tmpfs). ```python import os import sys import tempfile from dotenv import set_key ##### Pre-condition: /tmp must be on a different device than the target directory. tmp_dev = os.stat("/tmp").st_dev home_dev = os.stat(os.path.expanduser("~")).st_dev assert tmp_dev != home_dev, "Skipped: /tmp and ~ are on the same device (no cross-device move)" with tempfile.TemporaryDirectory(dir=os.path.expanduser("~")) as workdir: # File an attacker wants to overwrite target = os.path.join(workdir, "victim_config.txt") with open(target, "w") as f: f.write("DB_PASSWORD=supersecret\n") # Attacker pre-places a symlink at the path the application will use as .env env_symlink = os.path.join(workdir, ".env") os.symlink(target, env_symlink) before = open(target).read() # Application writes a new key -- triggers the cross-device fallback set_key(env_symlink, "INJECTED", "attacker_value") after = open(target).read() print("Before:", repr(before)) print("After: ", repr(after)) print("Symlink target overwritten:", target) ``` **Expected output:** ``` Before: 'DB_PASSWORD=supersecret\n' After: "DB_PASSWORD=supersecret\nINJECTED='attacker_value'\n" Symlink target overwritten: /home/user/tmp806nut2g/victim_config.txt ``` ##### Remediation The fix changes the `rewrite()` context manager in the following ways: 1. **Symlinks are no longer followed by default.** When the `.env` path is a symlink, `rewrite()` now resolves it to the real path before proceeding, or (by default) operates on the symlink entry itself rather than the target. 2. **A `follow_symlinks: bool = False` parameter** is added to `set_key()` and `unset_key()` for users who explicitly need the old behavior. 3. **Temp files are written in the same directory** as the target `.env` file (instead of the system temp directory), eliminating the cross-device rename condition entirely. 4. **`os.replace()` is used instead of `shutil.move()`**, providing atomic replacement without symlink-following fallback behavior. Users are advised to upgrade to the patched version as soon as it is available on PyPI. ##### Timeline | Date | Event | | ------------ | ---------------------------------------------------------------------------------------------------- | | 2026-01-09 | Initial report received from Giorgos Tsigourakos regarding a separate, unrelated issue also located in `rewrite()` | | 2026-01-10 | Co-maintainer acknowledged report, requested clarification | | 2026-01-11 | Initial report assessed as not exploitable and closed | | 2026-02-24 | Reporter identified new, distinct cross-device symlink attack vector with deterministic exploitation | | 2026-02-26 | Co-maintainer confirmed vulnerability and shared draft patch | | 2026-02-26 | Reporter validated fix with monkeypatched PoC, proposed CVSS | | 2026-03-01 | Patch merged to main | | 2026-03-01 | Patched version released to PyPI | | 2026-04-20 | Advisory published | ##### Patches Upgrade to v.1.2.2 or use the patch from https://github.com/theskumar/python-dotenv/commit/790c5c02991100aa1bf41ee5330aca75edc51311.patch #### Severity - CVSS Score: 6.6 / 10 (Medium) - Vector String: `CVSS:3.1/AV:L/AC:L/PR:L/UI:R/S:U/C:N/I:H/A:H` #### References - [https://github.com/theskumar/python-dotenv/security/advisories/GHSA-mf9w-mj56-hr94](https://github.com/theskumar/python-dotenv/security/advisories/GHSA-mf9w-mj56-hr94) - [https://nvd.nist.gov/vuln/detail/CVE-2026-28684](https://nvd.nist.gov/vuln/detail/CVE-2026-28684) - [https://github.com/theskumar/python-dotenv/commit/790c5c02991100aa1bf41ee5330aca75edc51311](https://github.com/theskumar/python-dotenv/commit/790c5c02991100aa1bf41ee5330aca75edc51311) - [https://github.com/theskumar/python-dotenv/commit/790c5c02991100aa1bf41ee5330aca75edc51311.patch](https://github.com/theskumar/python-dotenv/commit/790c5c02991100aa1bf41ee5330aca75edc51311.patch) - [https://github.com/theskumar/python-dotenv](https://github.com/theskumar/python-dotenv) - [https://github.com/theskumar/python-dotenv/releases/tag/v1.2.2](https://github.com/theskumar/python-dotenv/releases/tag/v1.2.2) This data is provided by [OSV](https://osv.dev/vulnerability/GHSA-mf9w-mj56-hr94) and the [GitHub Advisory Database](https://github.com/github/advisory-database) ([CC-BY 4.0](https://github.com/github/advisory-database/blob/main/LICENSE.md)). </details> --- ### [CVE-2026-28684](https://nvd.nist.gov/vuln/detail/CVE-2026-28684) / [GHSA-mf9w-mj56-hr94](https://github.com/advisories/GHSA-mf9w-mj56-hr94) / PYSEC-2026-2270 <details> <summary>More information</summary> #### Details python-dotenv reads key-value pairs from a .env file and can set them as environment variables. Prior to version 1.2.2, `set_key()` and `unset_key()` in python-dotenv follow symbolic links when rewriting `.env` files, allowing a local attacker to overwrite arbitrary files via a crafted symlink when a cross-device rename fallback is triggered. Users should upgrade to v.1.2.2 or, as a workaround, apply the patch manually. #### Severity - CVSS Score: 6.6 / 10 (Medium) - Vector String: `CVSS:3.1/AV:L/AC:L/PR:L/UI:R/S:U/C:N/I:H/A:H` #### References - [https://github.com/theskumar/python-dotenv/releases/tag/v1.2.2](https://github.com/theskumar/python-dotenv/releases/tag/v1.2.2) - [https://github.com/theskumar/python-dotenv/commit/790c5c02991100aa1bf41ee5330aca75edc51311](https://github.com/theskumar/python-dotenv/commit/790c5c02991100aa1bf41ee5330aca75edc51311) - [https://github.com/theskumar/python-dotenv/security/advisories/GHSA-mf9w-mj56-hr94](https://github.com/theskumar/python-dotenv/security/advisories/GHSA-mf9w-mj56-hr94) This data is provided by [OSV](https://osv.dev/vulnerability/PYSEC-2026-2270) and the [PyPI Advisory Database](https://github.com/pypa/advisory-database) ([CC-BY 4.0](https://github.com/pypa/advisory-database/blob/main/LICENSE)). </details> --- ### Configuration 📅 **Schedule**: (UTC) - Branch creation - At any time (no schedule defined) - Automerge - At any time (no schedule defined) 🚦 **Automerge**: Disabled by config. Please merge this manually once you are satisfied. ♻ **Rebasing**: Whenever PR becomes conflicted, or you tick the rebase/retry checkbox. 🔕 **Ignore**: Close this PR and you won't be reminded about this update again. --- - [ ] If you want to rebase/retry this PR, check this box --- This PR has been generated by [Mend Renovate](https://github.com/renovatebot/renovate).

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chore(deps): update dependency python-dotenv to v1.2.2 [security] #9

python-dotenv: Symlink following in set_key allows arbitrary file overwrite via cross-device rename fallback

Details

Summary

Details

Impact

Proof of Concept

Remediation

Timeline

Patches

Severity

References

CVE-2026-28684 / GHSA-mf9w-mj56-hr94 / PYSEC-2026-2270

Details

Severity

References

Configuration

Checkout

Merge