CVE-2026-49406 Deno: BYONM module resolution allows `package.json` main path traversal to bypass `--allow-read` restrictions
A path traversal in Deno's BYONM mode allows malicious packages to bypass read restrictions and access arbitrary files on disk.
- Exploited in the wild
- Not known
- Login needed
- Any signed-in user
- Attackable
- Local or same network only
- Victim action needed
- Not needed
- Fix
- Available
What is CVE-2026-49406?
CVE-2026-49406 is a medium-severity path traversal vulnerability in denoland deno, published on 23 Jun 2026. It can only be exploited from the same machine or local network, with no action from the victim.
Official description
Deno is a JavaScript, TypeScript, and WebAssembly runtime. Prior to 2.7.12, when Deno was run in BYONM mode (nodeModulesDir: "manual"), the module resolver did not validate that a package's resolved entrypoint stayed within its node_modules/<pkg>/ directory. A malicious package.json whose main field contained .. segments was able to resolve to an arbitrary path on disk, and the resolver then read that file without consulting the --allow-read allowlist. This let a require("evil-pkg") call return the contents of a file that a direct Deno.readTextFileSync(...) call would have been blocked from reading. This vulnerability is fixed in 2.7.12.
Weakness: CWE-22
Which versions are affected by CVE-2026-49406?
2 open source packages ship an affected version, including deno. It affects 1 product.
| Package | Affected | Fixed in |
|---|---|---|
deno crates.io | All versions | 2.7.12 |
deno crates.io | All versions | 2.7.12 |
Products include Deno Deno.
How do I fix CVE-2026-49406?
Upgrade deno to 2.7.12 or later.
Upgrade, and resolve every user-supplied path against an allowed base folder before opening it. More about Path traversal.
Is CVE-2026-49406 being exploited?
It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-49406 exists.
Other vulnerabilities in denoland deno
- CVE-2023-28445 Deno improperly handles resizable ArrayBuffer
- CVE-2022-24783 Sandbox bypass leading to arbitrary code execution in Deno
- CVE-2021-32619 Static imports inside dynamically imported modules do not adhere to permission checks
- CVE-2026-22863 Deno node:crypto doesn't finalize cipher
- CVE-2024-27936 Deno interactive permission prompt spoofing via improper ANSI stripping
Sources
Also known as GHSA-968w-xfqw-vp9q, JLSEC-2026-657.