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

Exploitation

No confirmed exploitation recorded. Patch Next marks exploitation only from CISA KEV.

CVSS

5.5 · CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:N/A:N

EPSS

• CVE-2026-49406: 0.18% estimated exploitation activity in the next 30 days; percentile 7.09 (FIRST EPSS, 2026-11-03). This is a model estimate, not proof of exploitation or customer exposure.

As published by the source; long descriptions are shortened.

Summary When Deno was run in BYONM mode (nodeModulesDir: "manual"), the module resolver did not validate that a package's resolved entrypoint stayed within its nodemodules/<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. Details In BYONM mode, Deno resolved npm packages directly from a user-managed nodemodules tree. Resolution of require("pkg") proceeded by reading pkg/package.json, taking the main field, joining it to the package directory, and loading the result as a module. The path joined from main was not constrained to the package root. A package.json such as: resolved to nodemodules/pkg/../../../secret.json, escaping nodemodules entirely. The BYONM permission check…

Published by the source

16 Jun 2026, 19:11 UTC

Last modified by the source

20 Jul 2026, 13:43 UTC

Source last checked

26 Oct 2026, 15:43 UTC

1. Revision 1 · created · 26 Oct 2026

   Published from ghsa record GHSA-968w-xfqw-vp9q

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# Patch Next advisory brief: CVE-2026-49406

Advisory: Deno: BYONM module resolution allows `package.json` main path traversal to bypass `--allow-read` restrictions
IDs: CVE-2026-49406, GHSA-968w-xfqw-vp9q
Record: https://patchnext.com/advisories/cve-2026-49406 (revision 1, source checked 26 Oct 2026, 15:43 UTC)
Inventory: none attached. This brief comes from a public page and does not say whether any deployment is affected.
Severity: Medium (CVSS 5.5)
Exploitation: no confirmed exploitation recorded. Patch Next confirms exploitation only from CISA KEV.
Vendor response: Vendor fix available; fixed versions by package: deno 2.7.12. A vendor fix does not mean a deployment is fixed.

## Affected components
- crates.io deno: affected <= 2.7.11; fixed in 2.7.12

## Suggested inspection (read-only)
- crates.io deno: check the installed version with your package manager.

## Supported action
Upgrade each affected component to a fixed version on its release line. For a transitive dependency, upgrade the parent package or add an override or constraint, then regenerate the lockfile. Redeploy every environment that ran an affected version.

## Required regression checks
- Run the test suite and a production build.
- Exercise the features that depend on deno.
- Repeat the inspection and confirm that only fixed versions remain installed.

## Rollback considerations
- Keep the previous lockfile and deployment artifact. Rolling back reinstates the vulnerable version, so apply any documented mitigation while you fix forward.

## Unresolved questions
- Which deployments run an affected version?
- Exploitation status can change. Check again before lowering the priority.
- Mark the work resolved only after the fixed version is verified in production.

## Sources
- Verified: https://github.com/advisories/GHSA-968w-xfqw-vp9q (GitHub-reviewed advisory GHSA-968w-xfqw-vp9q lists affected ranges: crates.io deno >=0 <=2.7.11)

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