CVE-2026-49983
Official description Straight from the sourceThe vendor's or NVD's own wording, published unedited. Authoritative, but often terse — it says what broke, rarely what to do.
NVD · uneditedDeno is a JavaScript, TypeScript, and WebAssembly runtime. Prior to 2.8.1, 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. This vulnerability is fixed in 2.8.1.
Technical summary Written by usOur analysis, written from the advisory, the CVSS vector and the affected-version data. It adds context the advisory leaves out, and never invents facts that are not in the source.
dbcve analysis · high confidenceIn Deno prior to 2.8.1, the process.loadEnvFile() API bypasses the env permission system. Even when --deny-env is set, loadEnvFile() will write all variables from a .env file into process.env, provided the attacker has read access to the .env file. This allows environment variable injection through a malicious or writable .env file.
Verify against the referenced sources before acting — the references below are authoritative for this CVE, this summary is not.
Affected products & versions What the vendor confirmedThe version ranges the vendor confirmed as vulnerable. If your version sits inside a range here, treat yourself as exposed until you have upgraded.
NVD · CPE data>= 2.3.0, < 2.8.1CVSS breakdown How the score is builtThe industry scoring standard. It rates how the flaw is reached, what it takes to exploit, and what an attacker gains — the score is derived from those, not the other way round.
From the vector- Attack vector
- Local
- Complexity
- Low
- Privileges
- Low
- User interaction
- None
- Scope
- Changed
- Confidentiality
- Low
- Integrity
- Low
- Availability
- None
CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:C/C:L/I:L/A:N
Am I affected? How to checkSteps we derive from the advisory and the affected-version data, so you can decide whether this CVE reaches your setup. They are a guide, not a scan — your own configuration is the authority.
dbcve checksWork through these to decide whether this CVE applies to you.
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Check installed Deno versionRun `deno --version` and compare the version number to the affected range (>= 2.3.0 and < 2.8.1)Affected if The installed version is between 2.3.0 and 2.8.0 inclusive
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Identify use of process.loadEnvFile()Search codebase for `loadEnvFile` or `Deno.loadEnvFile` calls in source filesAffected if The codebase contains calls to process.loadEnvFile() or Deno.loadEnvFile()
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Verify .env file existenceCheck for .env, .env.local, or other environment file variants in the project directoryAffected if A .env file exists and could be read or modified by an attacker
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Check permission flags in useReview runtime permission flags such as --deny-env, --allow-env, or granular env permissions in run commands or deno.json configurationAffected if The application relies on --deny-env or restrictive env permissions while using loadEnvFile()
You are affected if you run Deno version 2.3.0 through 2.8.0, use process.loadEnvFile() in your code, and depend on --deny-env to restrict environment variable access.
Generated from the published advisory. Verify against your own configuration.
Remediation Closing itWhat it takes to close this. Where a vendor fix exists we point at it; where none exists we say so plainly, and can build one. Effort estimates are scoped from the advisory, not from your codebase.
dbcve · scoped2.8.1
Upgrade Deno to version 2.8.1 or later where the vulnerability is fixed. Avoid using process.loadEnvFile() in untrusted code contexts until the upgrade is applied.
Deno 2.8.1
- Upgrade Deno to version 2.8.1 or later by running: deno upgrade
- Verify the fix by running a test script with both --allow-read and --deny-env flags to confirm process.loadEnvFile() now properly respects the env permission
Generated from the published advisory — verify against the referenced sources before acting.
- Consultation1.0 h
- Implementation1.0 h
- Testing2.0 h
- Review / QA1.0 h
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Scan for this in your stack
Free · runs locallyCheck whether your project pulls in CVE-2026-49983 — or any other known-vulnerable package — straight from your lock files. Free and open source; it runs locally and uploads nothing.
References Go to the primary sourcePrimary sources — vendor advisories, patches and trackers. Where our summary and a reference disagree, the reference wins.
Primary sourcesPractitioner notes
ContributedPeer-ranked notes from engineers who’ve handled CVE-2026-49983 in production — separate from our analysis above.
The advisory tells you what broke. It rarely tells you what actually worked. If you’ve dealt with this one, that detail is what the next engineer is searching for.
- The version that genuinely resolved it — not the one the vendor claimed
- A config change or rule that shut the vector down
- A gotcha in the upgrade path that cost you an afternoon
No notes yet
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- Version or environment caveats, and links to real fixes
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