Vulnerability-Lookup

CVE-2026-49983 (GCVE-0-2026-49983)

Vulnerability from cvelistv5 – Published: 2026-06-23 17:16 – Updated: 2026-06-23 17:54

Title

Deno: process.loadEnvFile() bypasses env permission checks and mutates process.env with only read access

Summary

Deno 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.

Severity

5.2 (Medium)


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

SSVC

Exploitation: none Automatable: no Technical Impact: partial

CISA Coordinator (v2.0.3)

CWE

CWE-863 - Incorrect Authorization

Assigner

GitHub_M

References

1 reference

URL	Tags
https://github.com/denoland/deno/security/advisor…	x_refsource_CONFIRM

Impacted products

1 product

Vendor	Product	Version
denoland	deno	Affected: < 2.8.1

Show details on NVD website

JSON

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{
  "containers": {
    "adp": [
      {
        "metrics": [
          {
            "other": {
              "content": {
                "id": "CVE-2026-49983",
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                  },
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                    "Technical Impact": "partial"
                  }
                ],
                "role": "CISA Coordinator",
                "timestamp": "2026-06-23T17:54:45.354967Z",
                "version": "2.0.3"
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        }
      ],
      "metrics": [
        {
          "cvssV3_1": {
            "attackComplexity": "LOW",
            "attackVector": "LOCAL",
            "availabilityImpact": "NONE",
            "baseScore": 5.2,
            "baseSeverity": "MEDIUM",
            "confidentialityImpact": "LOW",
            "integrityImpact": "LOW",
            "privilegesRequired": "LOW",
            "scope": "CHANGED",
            "userInteraction": "NONE",
            "vectorString": "CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:C/C:L/I:L/A:N",
            "version": "3.1"
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      },
      "references": [
        {
          "name": "https://github.com/denoland/deno/security/advisories/GHSA-4c8g-jvcx-v4hv",
          "tags": [
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          "url": "https://github.com/denoland/deno/security/advisories/GHSA-4c8g-jvcx-v4hv"
        }
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        "discovery": "UNKNOWN"
      },
      "title": "Deno: process.loadEnvFile() bypasses env permission checks and mutates process.env with only read access"
    }
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  "cveMetadata": {
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    "datePublished": "2026-06-23T17:16:17.026Z",
    "dateReserved": "2026-06-02T18:30:51.282Z",
    "dateUpdated": "2026-06-23T17:54:51.686Z",
    "state": "PUBLISHED"
  },
  "dataType": "CVE_RECORD",
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      "percentile": "0.02233"
    },
    "vulnrichment": {
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GHSA-4C8G-JVCX-V4HV

Vulnerability from github – Published: 2026-06-16 19:04 – Updated: 2026-06-16 19:04

Summary

Deno: process.loadEnvFile() bypasses env permission checks and mutates process.env with only read access

Details

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() from node:process.
You rely on Deno's permission model — specifically --deny-env, an --allow-env=… allowlist, or running without granting env — as a security boundary.
The .env path passed to loadEnvFile() 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-read grant.

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.

Severity

5.2 (Medium)


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

Show details on source website

JSON

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{
  "affected": [
    {
      "database_specific": {
        "last_known_affected_version_range": "\u003c= 2.8.0"
      },
      "package": {
        "ecosystem": "crates.io",
        "name": "deno"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "0"
            },
            {
              "fixed": "2.8.1"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ]
    }
  ],
  "aliases": [
    "CVE-2026-49983"
  ],
  "database_specific": {
    "cwe_ids": [
      "CWE-863"
    ],
    "github_reviewed": true,
    "github_reviewed_at": "2026-06-16T19:04:57Z",
    "nvd_published_at": null,
    "severity": "MODERATE"
  },
  "details": "## Summary\n\nIn Deno, environment access is gated by the `env` permission. You can deny it\nwith `--deny-env`, or restrict it to a specific allowlist with\n`--allow-env=FOO,BAR`. The expectation is that a program running without `env`\npermission cannot change `process.env`.\n\n`process.loadEnvFile()` (the Node-compatible API for loading variables from a\n`.env` file) does **not** honor this. It only checks that the program has\n**read** permission for the dotenv file, then writes every key in that file\ninto the process environment \u2014 even when `env` access is denied.\n\nIn effect, **`--allow-read` plus a writable or attacker-controlled `.env` file\nis enough to defeat `--deny-env`.**\n\n## Am I affected?\n\nYou are potentially affected if **all** of the following are true:\n\n1. You run Deno **v2.3.0 or newer**.\n2. Your program (or any dependency it imports) calls `process.loadEnvFile()`\n   from `node:process`.\n3. You rely on Deno\u0027s permission model \u2014 specifically `--deny-env`, an\n   `--allow-env=\u2026` allowlist, or running without granting `env` \u2014 as a\n   security boundary.\n4. The `.env` path passed to `loadEnvFile()` can be controlled or modified by\n   a less-trusted party (untrusted input, user-writable directory, third-party\n   dependency, etc.) and is covered by your `--allow-read` grant.\n\nIf your program does not use `process.loadEnvFile()` at all, or if it already\ngrants full `env` access, this advisory does not change your risk.",
  "id": "GHSA-4c8g-jvcx-v4hv",
  "modified": "2026-06-16T19:04:57Z",
  "published": "2026-06-16T19:04:57Z",
  "references": [
    {
      "type": "WEB",
      "url": "https://github.com/denoland/deno/security/advisories/GHSA-4c8g-jvcx-v4hv"
    },
    {
      "type": "PACKAGE",
      "url": "https://github.com/denoland/deno"
    }
  ],
  "schema_version": "1.4.0",
  "severity": [
    {
      "score": "CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:C/C:L/I:L/A:N",
      "type": "CVSS_V3"
    }
  ],
  "summary": "Deno: process.loadEnvFile() bypasses env permission checks and mutates process.env with only read access"
}

Sightings

Author	Source	Type	Date	Other

Nomenclature

Seen: The vulnerability was mentioned, discussed, or observed by the user.
Confirmed: The vulnerability has been validated from an analyst's perspective.
Published Proof of Concept: A public proof of concept is available for this vulnerability.
Exploited: The vulnerability was observed as exploited by the user who reported the sighting.
Patched: The vulnerability was observed as successfully patched by the user who reported the sighting.
Not exploited: The vulnerability was not observed as exploited by the user who reported the sighting.
Not confirmed: The user expressed doubt about the validity of the vulnerability.
Not patched: The vulnerability was not observed as successfully patched by the user who reported the sighting.

Detection rules are retrieved from Rulezet.

Action not permitted

CVE-2026-49983 (GCVE-0-2026-49983)

GHSA-4C8G-JVCX-V4HV

Summary

Am I affected?

Tags

Sightings

Nomenclature