GHSA-4c8g-jvcx-v4hv
MEDIUMGHSA-4c8g-jvcx-v4hv is a medium-severity (CVSS 5.2) CWE-863 vulnerability in deno. O3 Security confirms whether GHSA-4c8g-jvcx-v4hv is actually reachable in your code before you act, and blocks exploitation at runtime until you patch.
Deno: process.loadEnvFile() bypasses env permission checks and mutates process.env with only read access
Blast Radius
denoReal-time download stats are indexed for npm and PyPI packages. This vulnerability affects crates.io packages — download data is not available via public APIs for these ecosystems.
Description
Summary
In Deno, environment access is gated by the env permission. You can deny it
with --deny-env, or restrict it to a specific allowlist with
--allow-env=FOO,BAR. The expectation is that a program running without env
permission cannot change process.env.
process.loadEnvFile() (the Node-compatible API for loading variables from a
.env file) does not honor this. It only checks that the program has
read permission for the dotenv file, then writes every key in that file
into the process environment — even when env access is denied.
In effect, --allow-read plus a writable or attacker-controlled .env file
is enough to defeat --deny-env.
Am I affected?
You are potentially affected if all of the following are true:
- You run Deno v2.3.0 or newer.
- Your program (or any dependency it imports) calls
process.loadEnvFile()fromnode:process. - You rely on Deno's permission model — specifically
--deny-env, an--allow-env=…allowlist, or running without grantingenv— as a security boundary. - The
.envpath passed toloadEnvFile()can be controlled or modified by a less-trusted party (untrusted input, user-writable directory, third-party dependency, etc.) and is covered by your--allow-readgrant.
If your program does not use process.loadEnvFile() at all, or if it already
grants full env access, this advisory does not change your risk.
Affected Packages
| Ecosystem | Package | Vulnerable range | Fix |
|---|---|---|---|
| 🦀crates.io | deno | all versions | 2.8.1 |
Detection & mitigation playbook
Open-source dependencyDetect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for deno. O3's reachability analysis confirms whether the vulnerable code path is actually invoked in your application, so you act on real exposure instead of every transitive match.
Fix
Update deno to 2.8.1 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms GHSA-4c8g-jvcx-v4hv is resolved across your whole dependency graph.
Workarounds
If you can't upgrade right away: gate or disable the affected feature, validate untrusted input at the boundary, and avoid passing attacker-controlled data into the vulnerable path. O3's runtime protection blocks exploitation in production as an interim safeguard until the upgrade lands.
How O3 protects you
O3 pinpoints whether GHSA-4c8g-jvcx-v4hv is reachable in your code and exactly where to fix it, then blocks exploitation in production at runtime until the patched version is deployed.
Tailored to GHSA-4c8g-jvcx-v4hv. Runtime protection reduces exposure until a permanent patch is applied and verified — it complements patching, it doesn't replace it.
Frequently Asked Questions
Is GHSA-4c8g-jvcx-v4hv in your dependencies?
O3 detects GHSA-4c8g-jvcx-v4hv across crates.io dependencies and uses function-level reachability to confirm whether the vulnerable code path is actually reachable — not just present. No false positives.