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7.5
Deno: Malicious Programs Can Trick Users into Granting Access
JLSEC-2026-100
Summary
If you use Deno's permission prompts, a malicious program can trick users into granting access by clearing the screen and displaying a fake message. This only affects users who run Deno in an interactive environment, such as a terminal. To fix this, update to Deno version 1.29.3 or use the --no-prompt flag to disable interactive prompts.
What to do
- Update deno_jll to version 1.33.4+0.
Affected software
| Vendor | Product | Affected versions | Fix available |
|---|---|---|---|
| – | deno_jll | <= 1.33.4+0 | 1.33.4+0 |
Original title
Deno is vulnerable to race condition via interactive permission prompt spoofing
Original description
### Impact
Multi-threaded programs were able to spoof interactive permission prompt by rewriting the prompt to suggest that program is waiting on user confirmation to unrelated action.
A malicious program could clear the terminal screen after permission prompt was shown and write a generic message like so:
```
// Expected prompt
⚠️ ┌ Deno requests read access to "./log.txt".
├ Requested by `Deno.open()` API
├ Run again with --allow-read to bypass this prompt.
└ Allow? [y/n] (y = yes, allow; n = no, deny) >
// Prompt that users would see
Do you want to continue?
```
This situation impacts users who use Web Worker API and relied on interactive permission prompt. The reproduction is very timing sensitive and can’t be reliably reproduced on every try.
This problem can not be exploited on systems that do not attach an interactive prompt (for example headless servers).
### Patches
The problem has been fixed in Deno v1.29.3; it is recommended all users update to this version.
### Workarounds
Run with `--no-prompt` flag to disable interactive permission prompts.
Multi-threaded programs were able to spoof interactive permission prompt by rewriting the prompt to suggest that program is waiting on user confirmation to unrelated action.
A malicious program could clear the terminal screen after permission prompt was shown and write a generic message like so:
```
// Expected prompt
⚠️ ┌ Deno requests read access to "./log.txt".
├ Requested by `Deno.open()` API
├ Run again with --allow-read to bypass this prompt.
└ Allow? [y/n] (y = yes, allow; n = no, deny) >
// Prompt that users would see
Do you want to continue?
```
This situation impacts users who use Web Worker API and relied on interactive permission prompt. The reproduction is very timing sensitive and can’t be reliably reproduced on every try.
This problem can not be exploited on systems that do not attach an interactive prompt (for example headless servers).
### Patches
The problem has been fixed in Deno v1.29.3; it is recommended all users update to this version.
### Workarounds
Run with `--no-prompt` flag to disable interactive permission prompts.
osv CVSS3.1
7.5
Published: 14 Apr 2026 · Updated: 14 Apr 2026 · First seen: 14 Apr 2026