CVE-2026-49406: Deno: BYONM module resolution allows `package.json` main path traversal to bypass `--allow-read` restrictions

Severity: medium (CVSS 5.5 v3.1)
Exploited in the wild: not listed in CISA KEV
EPSS: 0.2% probability of exploitation in the next 30 days
Public exploit or detection template: yes
Published: 2026-06-23 · updated 2026-10-25
Weakness: CWE-22

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.

Affected products

denoland deno: before 2.7.12 — fixed in 2.7.12

How to fix

Upgrade to a fixed version: denoland deno 2.7.12. Check the vendor advisory for mitigations.

References

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